poison

any agent that may produce chemically an injurious or deadly effect when introduced into the body in sufficient quantity. Some poisons can be deadly in minute quantities, others only if relatively large amounts are involved. Factors of importance in determining the severity of a poison include the nature of the poison itself, the concentration and amount, the route of administration, the length of exposure, and the age, size, and physical health of the individual. If poisoning is suspected a physician or poison control center should be called immediately. The remainder of the poison and its container should be saved; the label may list ingredients, first aid measures, or antidotes. For most ingested poisons emptying the stomach is the most important treatment; vomiting is best accomplished in the conscious individual by administering syrup of ipecac with large quantities of water. The major exceptions to this treatment are in cases of ingestion of corrosives, such as lye, and certain hydrocarbons, such as kerosene. In corrosive ingestions a small amount of milk may be given, but vomiting should not be induced since the damage that may have already been sustained by the mucous membranes of the esophagus and stomach may advance to perforation; the patient should be seen by a physician as soon as possible. Hydrocarbons are extremely volatile, and the dangers of their being aspirated into the lungs when vomiting is induced are greater than their toxicity if absorbed into the body. In gas or vapor poisoning the patient should be carried to a nonpolluted atmosphere; artificial respiration should be employed if necessary. If any poison has been absorbed through the skin, all contaminated garments should be removed immediately and the skin washed with soap and water. Poisoning is a significant cause of accidental death in children and is best treated by prevention; potential poisons in the home should be stored in locked cabinets. In chemistry, poison refers to a substance that inhibits or slows a chemical reaction. See separate articles on botulism; carbon monoxide; food poisoning; lead poisoning; mercury poisoning; poison gas; poison ivy; snakebite; toxin.












poliomyelitis

poliomyelitis or polio,or infantile paralysis is an acute viral infection, mainly of children but also affecting older persons. There are three immunologic types of poliomyelitis virus; exposure to one type produces immunity only to that type, so infection with the other types is still possible. Spread of the infection is primarily through contact with an infected person. Most people who contract polio either exhibit no symptoms or experience only minor illness; however, such individuals can harbor the virus and spread it to others. Less than 1% of the people who get infected develop paralysis.

The virus enters the body by way of the mouth, invades the bloodstream, and may be carried to the central nervous system, where it causes lesions of the gray matter of the spinal cord and brain. The illness begins with fever, headache, stiff neck and back, and muscle pain and tenderness. If there is involvement of the central nervous system, paralysis ensues. Of those patients who develop paralytic poliomyelitis, about 25% sustain severe permanent disability, another 25% have mild disabilities, and 50% recover with no residual paralysis. The disease is usually fatal if the nerve cells in the brain are attacked (bulbar poliomyelitis), causing paralysis of essential muscles, such as those controlling swallowing, heartbeat, and respiration. There is no specific drug for treatment. For reasons not clearly understood, some people who have had severe polio experience postpolio syndrome, a condition in which new weakness and pain occurs years later in previously affected muscles.

The incidence of poliomyelitis declined radically in the United States when a mass immunization program with the Salk vaccine, a preparation made from killed organisms and injected, was begun in 1955. By 1961 the Sabin vaccine, a preparation made from weakened living organisms and taken orally, was released for use. Since then the disease has been virtually eliminated in the Americas, Europe, and Australasia, but vaccination programs continue because of polio's existence in other parts of the world (mainly South Asia and parts of East and West Africa) and the ease of travel.

In 1988 the World Health Organization began a global vaccination campaign to eradicate the disease—which continued to paralyze hundreds of thousands of children each year—by 2000. Although the date of eradication was later pushed back to 2005 (and even later a set deadline was abandoned), by 2003 there were less than a thousand new cases of polio worldwide. In 2003–4 the campaign was slowed when Muslim states in N Nigeria refused to use vaccines they believed would sterilize women, leading to an increase in cases there and in neighboring countries and to outbreaks of the disease in 17 countries including Yemen and Indonesia. Some other African countries also experienced new outbreaks of the disease from other sources. However, by early 2007, polio was, according to WHO, endemic in India, Pakistan, Afghanistan, and Nigeria. Other experts also classified cases in Somalia and Ethiopia as endemic, and the status of the disease in Congo (Kinshasa), where civil war had long disrupted medical care, was unclear.










polycythemia

condition characterized by an increase in the production of red blood cells, or erythrocytes, in the blood. Primary polycythemia, also called erythremia, or polycythemia vera, is a chronic, progressive disease, most common in middle-aged men. It is characterized by overgrowth of the bone marrow, abnormally increased red blood cell production, and an enlarged spleen. Symptoms, include headache, inability to concentrate, and pain in the fingers and toes. There is a danger of blood clotting or hemorrhage (see thrombosis). Primary polycythemia is treated by radiation, periodic removal of some blood (phlebotomy), or chemotherapy with antimetabolite drugs, e.g., Cytoxan. In secondary polycythemia, or erythrocytosis, the proliferation of red blood cells results from the body's attempt to compensate for other conditions, such as prolonged lack of oxygen at high altitudes or chronic lung or heart insufficiency. Certain tumors are also associated with increased red blood cell production. In secondary polycythemia the treatment is directed toward the underlying cause.












polyp

polyp, in medicine, a benign tumor occurring in areas lined with mucous membrane such as the nose, gastrointestinal tract (especially the colon), and the uterus. Some polyps are pedunculated tumors, i.e., they grow on stems; others, attached by a broad base, are called sessile. Nasal polyps are usually associated with an allergic condition; since they interfere with breathing, it is advisable that they be removed. Uterine and gastrointestinal polyps are likely to cause bleeding, but, more important, they may undergo malignant degeneration and for this reason are also usually removed.













prostate cancer

The canceroriginating in the prostate gland. Prostate cancer is the leading malignancy in men in the United States and is second only to lung cancer as a cause of cancer death in men. It occurs predominantly in older men; the median age at diagnosis is 72 years. Black men have a higher incidence than white men. The cause of prostate cancer is unknown, but the incidence varies markedly by geographic region, an indication that there are environmental factors that may trigger the disease. For example, men in China and Japan have a low rate of prostate cancer, but the incidence rises in Chinese and Japanese men who move to the United States. The hormone testosterone is believed to have a role in the development of prostate cancer, and studies have shown a relationship between high dietary fat intake and increased testosterone levels. Prostate tumors are often slow growing. Around 95% are classified as adenocarcinomas (arising from epithelial glandular tissue). The most common site of metastasis is the bone.


Screening and Diagnosis

Traditionally, prostate cancer screening consisted of digital-rectal examination. Since 1986, however, a blood test for a tumor marker called prostate-specific antigen (PSA) has greatly increased the number of early-stage prostate cancers diagnosed. An elevated level of PSA can indicate the presence of prostatic malignancy. Elevated PSA is further investigated by an ultrasound test and needle biopsy, in which a fine needle is inserted into the gland and cells are extracted for laboratory analysis. In some cases a bone scan is also performed to rule out metastatic disease. Because PSA tests detect not only aggressive cancers but slow-growing cancers that are not life-threatening, many people disagree with routine PSA testing of asymptomatic men, fearing that the test might lead to unnecessary anxiety or treatments that compromise quality of life without assuring a longer life than a man ignorant of his condition would enjoy.


Treatment

For most patients with localized tumors, surgical removal of the prostate gland (prostatectomy) is the initial treatment, despite possible side effects of urinary incontinence and impotence. Localized prostate cancer can often be cured. After surgery, a repeated blood test for protein-specific antigen can indicate whether any cancer remains. In metastatic disease, other treatments are employed depending on the stage of the disease and the age and health of the patient. Treatment options include external-beam radiation, implantation of radioactive isotopes, and palliative surgery. Hormonal manipulation by giving estrogens or other drugs, or by orchiectomy (removal of the testes), is sometimes used to decrease levels of testosterone. Very small cancers or slow-growing cancers in older men are sometimes watched, but not treated, without compromising life expectancy. Experimental treatments under investigation include cryosurgery, destroying the tumor by freezing.











premenstrual syndrome

premenstrual syndrome (PMS), any of various symptoms experienced by women of childbearing age in the days immediately preceding menstruation. It is most common in women in their twenties and thirties. Some 70%–90% of menstruating women are said to have PMS on a cyclical basis. There are over 150 symptoms associated with the syndrome, including behavioral changes, eating binges, moodiness, irritability, fatigue, fluid retention, breast tenderness, and headaches. Some women have mild symptoms; others have symptoms that interfere with work or home life. A few are completely incapacitated, a condition called premenstrual dysphoric disorder. The symptoms vary from woman to woman, and each woman's symptoms may vary from month to month, making diagnosis difficult.

The exact cause is unknown. Hormonal imbalances, nutritional deficiencies, and neurotransmitter (serotonin and norepinephrine) fluctuations are being studied. PMS patients who have had hysterectomies may continue to have symptoms, but the symptoms in all patients disappear with menopause. There is no cure for PMS. In some women, dietary changes and exercise provide some relief through the loss of water weight, the alleviation of stress, and an increase in the production of endorphins. Antidepressants or antianxiety drugs are sometimes prescribed. In severe cases hormones that induce a premature menopause may be administered.











prickly heat

prickly heat (miliaria), inflammatory skin eruption due to obstruction of the sweat glands by keratin, the substance that forms the horny cells of the epidermis. It consists of blisterlike elevations with burning and itching, and is common in infants, obese persons, and those exposed to a hot, moist atmosphere for long periods of time. Relief may be obtained by applying soothing and drying lotions.











prion

An infectious agent thought to cause a group of diseases known as prion diseases. or transmissible spongiform encephalopathies. Well-known prion diseases are Creutzfeldt-Jakob disease (CJD) and kuru in humans, scrapie in sheep, bovine spongiform encephalopathy (BSE), also called “mad cow disease,” in cattle, and chronic wasting disease in deer and elk (wapiti). There is no effective treatment for any prion disease.

Sometimes taking more than 30 years to display symptoms, the diseases slowly attack brain tissue, often leaving spongelike holes. They are characterized by accumulations of abnormal forms of a protein, called prion protein, which, unlike viruses or bacteria, contain no genetic material and have no known ability to reproduce themselves. Normal prion proteins occur naturally in brain tissue. The abnormal form differs in shape from the normal prions and is not susceptible to enzymes that normally break down proteins. In the brain, abnormal prions appear to increase their number by directly converting normal prions.

Prion diseases have both infectious and hereditary components. The gene that codes for prions can mutate and be passed on to the next generation. Most of the diseases also can be acquired directly by infection, but unlike other infectious agents, prions provoke no immune response.

An epidemic of BSE in Great Britain that was diagnosed in 1986 and infected some 178,000 cows appears to have been caused by a protein feed supplement that contained rendered remains of scrapie-infected sheep brains. In 1996 a suspicion that BSE had been transmitted to humans who died of a variant of CJD in Britain caused a scientific and economic furor as the European Union imposed a ban (1996) on the export of British beef, which was partially lifted in 1999 and fully lifted in 2006. The U.S. Dept. of Agriculture banned the import of cattle and many cattle byproducts from most European nations because of BSE. Instances of BSE in cattle have also occurred in many other European countries, Canada, the United States, and Japan, but the vast majority of cases occurred in Britain in the 1980s. There is now compelling evidence that BSE is the same disease as variant CJD (vCJD), which ultimately killed more than 130 people, but it is not yet known exactly how the disease is passed from animals to humans.

The idea of disease-causing protein particles was first put forward in 1981 by Stanley B. Prusiner, the neurologist who coined the term prion (from proteinaceous infectious particle). The prion theory has been controversial from the beginning, and although scientific evidence for the existence of such infectious particles has increased, an exact causal link between prions and the diseases they are believed to cause remains to be established. Critics believe that these diseases are caused by unidentified viruses.











prostatitis

The inflammation of the prostate gland. Acute prostatitis is usually a result of infection in the urinary tract or infection carried by the blood; in many cases the infection spreads from the urethra and is contracted through sexual transmission. Symptoms include fever, low back pain, and difficulty or pain in urination; the gland is tender and swollen. Infection, caused by a variety of pathogenic bacteria and certain protozoans, is treated by an appropriate antibiotic. Healing is usually complete, but the condition may become chronic if the infecting organism persists.










psittacosis

psittacosis or parrot fever is an infectious disease caused by the species of Chlamydia psittaci and transmitted to people by birds, particularly parrots, parakeets, and lovebirds. In birds the disease takes the form of an intestinal infection, but in people the illness runs the course of a virus pneumonia; infection follows inhalation of dust from feathers or cage contents or the bite of an infected bird. Human psittacosis, which can be transmitted to others by cough droplets and sputum, is treated the same as pneumonia. The mortality rate may run as high as 30%. Restrictions on bird importation and attention to infected flocks of pigeons have been used to control the disease. Treatment with tetracycline antibiotic is usually effective.









psoriasis

occasionally acute but usually chronic and recurrent inflammation of the skin. The exact cause is unknown, but the disease appears to be an inherited, possibly autoimmune disorder that causes the overproduction of skin cells. Psoriasis may occur at any age but is uncommon in children. The characteristic lesion is a scaly “mother-of-pearl” patch, appearing anywhere on the body. Involvement may range from a single plaque to numerous patches that cover most of the skin. A variety of treatments are used for patients with mild to moderate cases. Treatments directed at the symptoms include the application of ointments and exposure to sunlight and ultraviolet (UVB) light. Retinoids help stabilize follicular epithelial cells. Vitamin D analogs and metabolites, although effective in treatment, have side effects. Photochemotherapy (psoralen combined with UVA radiation) is also effective, but increases the risk of skin cancer. Alfacept and other drugs that interfere with T-cell activation, and etanercept, infliximab, and other drugs that block tumor-necrosis factor are effective in many patients with moderate to severe psoriasis.









pus

thick white or yellowish fluid that forms in areas of infection such as wounds and abscesses. It is constituted of decomposed body tissue, bacteria (or other micro-organisms that cause the infection), and certain white blood cells. These white cells form one of the defense mechanisms of the body. Known as phagocytes, they rush to the area of infection and engulf the invading bacteria in a process called phagocytosis. Many white cells themselves succumb in the process and become one of the constituents of pus.











pyorrhea

inflammation and degeneration of the gums and other tissues surrounding the teeth. The onset of the disease is marked by bleeding of the gums. As the disease proceeds, the gums recede from the teeth, loosening of the teeth occurs, and the bone supporting the teeth is resorbed. Pus is discharged from pockets in the gums, which are formed as the jawbone recedes from the roots of the teeth. Pyorrhea, known medically as pyorrhea alveolaris, is most common in persons over 40. There are numerous possible causes, toward which therapy is directed, including poor nutrition, poor oral hygiene, ill-fitting dentures, and irritation of the tissues by dental tartar.

R

rabies

rabies or hydrophobia is an acute viral infection of the central nervous system in dogs, foxes, raccoons, skunks, bats, and other animals, and in humans. The virus is transmitted from an animal to a person, or from one animal to another, via infected saliva, most often by biting but also by the contact of torn skin with infected saliva. The virus travels from the bite or contact location to the spinal cord and brain. In humans the incubation period ranges from 10 days to a year or more. Symptoms are fever, uncontrollable excitement, and pronounced spasms of the throat muscles. Salivation is extreme, and despite great thirst the victim cannot swallow water; hence the misnomer hydrophobia (fear of water). Once symptoms develop, death (caused by convulsions, exhaustion, or paralysis) is usually inevitable.

Following a bite from a rabid or possibly rabid animal, preventive treatment involves administration of immune globulin for passive immunization followed by vaccinations over several weeks for active immunization. The only treatment after symptoms appear is rest and sedation. Dogs have been immunized from the time Louis Pasteur demonstrated a successful vaccine in 1885. Since then, human rabies has become rare in the United States and other industrialized countries due to comprehensive vaccination programs for domestic animals. Mass vaccination of susceptible animals in the wild with vaccine-laced bait has been used in an effort to stem an increase of rabies cases in the United States and Canada that began in the late 1980s. A similar wild animal vaccination program has been used with some success in parts of Europe.






radiation sickness

A harmful effect produced on body tissues by exposure to radioactive substances. The biological action of radiation is not fully understood, but it is believed that a disturbance in cellular activity results from the chemical changes caused by ionization (see ion). Some body tissues are more sensitive to radiation than others and are more easily affected; the cells in the blood-forming tissues (bone marrow, spleen, and lymph nodes) are extremely sensitive. Radiation sickness may occur from exposure to a single massive emanation such as a nuclear explosion (such as Hiroshima and Nagasaki), or it may occur after repeated large exposure or to even very small doses in a plant or laboratory, since radiation effects are cumulative. Moreover, exposure to the ultraviolet radiation of the sun can cause tissue destruction and trigger mutations that can lead to skin cancer. Radiation sickness may be fairly mild and transitory, consisting of weakness, loss of appetite, vomiting, and diarrhea. Since even in a mild dose of radiation the blood-forming tissue is destroyed to some extent, there is a reduction in the supply of blood cells and platelets. This increases the tendency to bleed and reduces the body's defense against infection. After a massive dose of radiation the reaction may be so severe that death quickly ensues. This is usually due to severe anemia or hemorrhage, to infection, or to dehydration. Extremely high doses damage the tissues of the brain, and death usually follows within 48 hr, as was demonstrated at Chernobyl. There is no treatment for radiation sickness, although it is sometimes possible for persons to survive otherwise lethal doses of radiation if bone marrow transplants are performed. Potassium iodide is to protect against thyroid cancer from radiation exposure, but the drug should ideally be taken four hours prior to the exposure. Exposure to radiation can cause genetic mutation; the progeny of those subjected to excessive radiation tend to show deleterious genetic changes. The genetic damage from the atomic bombs dropped on Japan is still evident and such damage will continue to surface in people directly affected by the nuclear diasaster at Chernobyl. Persons working with radioactive materials or X rays protect themselves from excessive exposure to radiation by shields and special clothing usually containing lead. Processes involving radioactive substances are observed through thick plates of specially prepared glass that exclude the harmful rays. A dosimeter, a device measuring the amount of radiation to which an individual has been exposed, is always worn by persons working in radioactive areas.










rash

nonspecific term for an eruption of the skin. It may result from skin allergy, skin irritation, or skin disease, or it may be a symptom of a systemic disease like measles, smallpox, or scarlet fever. A rash may appear as discolored spots or a general redness, or as blisters or pustules, either flat or raised above the surface of the skin. The rash may cause skin irritation—itching, tingling, burning, or pain—or it may not cause any discomfort. The appearance and distribution of a rash are often important factors for consideration in diagnosing a particular disease.










repetitive stress injury

repetitive stress injury or repetitive strain injury(RSI), injury caused by repeated movement of a particular part of the body. Often seen in workers whose physical routine is unvaried, RSI has become epidemic since computers have entered the workplace in large numbers. Many RSIs develop when the sheaths that cover muscle tendons swell and press on nerves. Constant typing can cause one form of RSI, carpal tunnel syndrome, a sometimes disabling pain and tingling in the thumb and first two fingers. It is caused by swelling and pressure on the median nerve passing through the wrist. Other common problems are rotator cuff injury, from overuse of the shoulder; tennis elbow, inflammation of a tendon in the elbow from overuse of the forearm; and back injuries from repeated heavy lifting. A 1998 report by the National Academy of Sciences in the United States called RSI a serious national problem, with financial costs ranging up to $20 billion annually.

Treatment of RSI usually begins with attempts to change the conditions that caused the injury. Often, exercises and anti-inflammatory drugs are prescribed; in some cases surgery is necessary. Many workers' compensation cases and lawsuits relating to RSI have been brought against employers and product manufacturers. To avoid the high costs of RSI, some businesses have introduced ergonomic workstations and enforced rest periods.










Reye's syndrome

rare but life-threatening disease characterized by acute encephalopathy and fatty infiltration of internal organs, especially the liver. It occurs almost entirely in children under age 15. The cause is unknown, but the disease usually follows an acute viral infection (particularly influenza or chicken pox), especially when aspirin or other salicylates have been given. The symptoms, which occur about a week after the virus infection, are vomiting and disorientation; these may be followed by seizures, coma, and respiratory arrest. Treatment is directed toward reducing brain swelling, correcting blood chemistry changes due to liver damage, and providing respiratory support if needed. Doctors recommend that children be given acetaminophen rather than aspirin for viral infections or fever.












rheumatic fever

systemic inflammatory disease, extremely variable in its manifestation, severity, duration, and aftereffects. It is frequently followed by serious heart disease, especially when there are repeated attacks. Rheumatic fever usually affects children. It is closely related to a preceding streptococcal infection (e.g., streptococcal tonsillitis or pharyngitis). Some of its symptoms are tenderness and inflammation about the joints, fever, jerky movements, nodules under the skin, and skin rash. If inflammation of the heart, or myocarditis, is mild, there is no permanent heart damage, but if the valves of the heart become inflamed, they may become scarred and deformed, permanently impairing their function. Such heart damage can sometimes be corrected by surgery.













rickets

bone disease caused by a deficiency of vitamin D or calcium. Essential in regulating calcium and phosphorus absorption by the body, vitamin D can be formed in the skin by ultraviolet rays contained in sunlight; it can also be consumed in such foods as fish oils, eggs, and butter. Since calcium and phosphorus are essential for proper development and hardening of bones, the disease manifests itself in children as softening of bones, abnormal bone growth, and enlargement of cartilage at the ends of long bones. Where bones must support weight, such as the legs and pelvis, the skeleton is likely to become bent or deformed. The result is often knock-knees, bowlegs, and deformities of the chest and pelvis. In temperate climates or the tropics, vitamin-D deficiency usually results from poor diet rather than from lack of exposure to ultraviolet rays of sunlight. Rickets is no longer common in developed countries because milk is readily obtained and is usually fortified with vitamin D; infants commonly receive vitamin D as a supplement. Treatment of rickets is largely preventive, i.e., by early recognition and by including adequate amounts of vitamin D and calcium in the diet.










rickettsia

any of a group of very small microorganisms, many disease-causing, that live in vertebrates and are transmitted by bloodsucking parasitic arthropods such as fleas, lice (see louse), and ticks. Rickettsias are named after their discoverer, the American pathologist Harold Taylor Ricketts, who died of typhus in Mexico after confirming the infectious agent of that rickettsial disease. Rickettsias are gram-negative, coccoid-shaped or rod-shaped bacteria; unlike other bacteria, but like viruses, they require a living host (a living cell) to survive. Rickettsias from infected vertebrates, usually mammals, live and multiply in the gastrointestinal tract of an arthropod carrier but do not cause disease there; they are transmitted to another vertebrate, possibly one of another species, by the arthropod's mouthparts or feces.

Types of Rickettsial Diseases

Rickettsia prowazekii causes louse-borne typhus, carried from person to person by two species of lice. Flea, or murine, typhus, caused by R. mooseri, is transmitted from rodents to people by fleas. Trench fever, caused by R. quintana, was an epidemic disease in World War I; it is transmitted by the rat flea from rat to person or from person to person. Trench fever disease reservoirs (perpetuation of the disease in wild animal populations) exist in some parts of E Europe, Mexico, and N Africa. Various typhuslike rickettsial diseases, such as Rocky Mountain spotted fever and African tick typhus, are transmitted by ticks from animal hosts to people. Mite-borne rickettsial infections include rickettsialpox, caused by Rickettsia akari and transmitted from house mice to people, and scrub typhus, or tsutsugamushi fever, caused by R. tsutsugamushi and found in Japan and SE Asia. Q fever, caused by Coxiella burnetii, a more hardy rickettsia viable outside the living host, is usually transmitted to humans by inhalation of contaminated airborne particles or from contaminated materials, often from infected livestock; it is an occupational hazard among dairy farm and slaughterhouse workers. A new rickettsia, Ehrlichia chaffeenis, which results in human ehrlichiosis, was identified in 1986.


Symptoms and Treatment

The similar symptoms of rickettsial infections often make it difficult to distinguish one disease from another. In people the organisms grow in cells lining blood and lymph vessels; a rash, fever, and flulike symptoms are usually present. Q fever also causes lung damage. All rickettsial diseases respond to treatment with antibiotics such as doxycycline (a tetracycline) and chloramphenicol.










rigor mortis

rigidity of the body that occurs after death. The onset may vary from about 10 min to several hours or more after death, depending on the condition of the body at death and on factors in the atmosphere, particularly temperature. Rigor mortis affects the facial musculature first and then spreads to other parts of the body. It is caused by chemical changes in the muscle tissue. The state of rigor usually lasts about 24 hours or until muscle decomposition takes place by acid formation.











ringworm

superficial eruption of the skin caused by a fungus, chiefly Microsporum, Trichophyton, or Epidermophyton. Any area of the skin may be affected, including the scalp and nails, but the most common site is the feet. That disorder is often called athlete's foot in the belief that the infection is contracted during the use of communal shower facilities. Actually, fungi are present on the bodies of most persons, but some individuals are more resistant to fungus invasion than others. Moreover, a prolonged moist, airless condition caused by excessive perspiration may subject a formerly resistant person to fungus invasion. Ringworm infection causes dry, scaly patches or blisterlike elevations, usually with burning or itching. Griseofulvin, a modified form of penicillin, is effective against scalp infection but is ineffective against foot fungi. In mild cases of athlete's foot, often the only treatment is to keep the feet scrupulously dry. In more persistent cases local antifungal ointments, sprays, or soaks are recommended.










river blindness

river blindness or onchocerciasis means disease caused by the parasitic nematode worm Onchocerca volvulus. The worm larvae are transmitted by the bites of blackflies (genus Simulium) that live in fast moving streams. Inside the body the worms form disfiguring skin nodules, where they mate. Their tiny larvae, or microfilariae, migrate through the skin, causing severe itching. If the infection reaches the area of the eye, allergic reaction to the microfilariae can cause blindness.

Tests can now detect infestation before the disease has progressed, and the new drugs ivermectin, which kills the larvae, and amocarzine, which kills adult forms, have begun to help control the disease. Blackfly eradication programs have had limited success because the flies can quickly develop resistance to pesticides.

River blindness, which occurs primarily in Africa, Central and South America, and Yemen, affects an estimated 18 million people. In Africa, two strains have been identified, a savanna strain and a forest strain. The forest strain does not usually lead to blindness, but it does cause severe skin symptoms (lesions, itching, discoloration, change in texture) that can result in social ostracism.








rubella

rubella or German measles can be defined as acute infectious disease of children and young adults. It is caused by a filterable virus that is spread by droplet spray from the respiratory tract of an infected individual. Rubella is a much milder infection than rubeola (measles) and the rash, appearing after an incubation period of two to three weeks, rarely lasts more than three days. The lymph nodes behind the ears become tender and swollen, but otherwise German measles is almost always uncomplicated. However, during the first trimester of pregnancy it is associated with an increased risk of congenital damage to the fetus, producing stillbirths, abortion, low birth weight, and such malformations as cardiac defects, eye defects (especially cataracts), and mental retardation. During the first 16 weeks of pregnancy the infection has been estimated to carry a risk of fetal damage of between 30% and 35%. Pregnant women who have been exposed to rubella are given gamma globulin in an effort to prevent the disease. Research to develop a vaccine that would confer immunity was spurred by an epidemic of rubella in 1964 and the evidently related rise in the number of birth deformities. A live attenuated vaccine has been developed and is given to girls from 15 months to puberty and often to boys as well. Approximately 13% to 15% of women develop acute arthitis from vaccination. Before the vaccine can be administered to an adult woman it must be determined that she is not pregnant, and the test for the presence of rubella antibodies (which would indicate immunity to the disease from previous exposure) is given. Birth control should be practiced for at least three months after receiving the vaccine.

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S

salmonellosis

any of a group of infectious diseases caused by intestinal bacteria of the genus Salmonella, including typhoid fever, paratyphoid fever, blood poisoning, and food poisoning (gastroenteritis).

Typhoid fever, caused by S. typhi, is spread by fecal contamination of water or milk or by food handlers who are carriers. It is characterized by a high fever and a rash on the chest and abdomen and can be fatal. Paratyphoid fever, caused by S. paratyphi, is also spread in the feces of victims or carriers. Outbreaks often occur where adequate hygiene, especially in food preparers, is not practiced. Paratyphoid is characterized by mild fever and a rash on the chest. Bacteremia is characterized by the presence of S. choleraesuis, S. typhimurium, or S. heidelberg in the blood. All three diseases are treated with the antibiotic chloramphenicol.

The most common form of salmonellosis is food poisoning caused by S. typhimurium and other Salmonella species. Sources of infection include eggs, beef, poultry, unpasteurized dairy products, and fruits and vegetables. In 1998 a new product called CF-3, or Preempt, which could reduce but not eliminate Salmonella in chickens, was approved for sale to poultry farmers. Delivered as a spray to newly hatched chicks, it consists of a mixture of beneficial bacteria that the mother hen normally transferred to her chicks before the advent of factory farms.

Outbreaks of salmonellosis food poisoning occasionally result from contaminated institutional or other mass-prepared food. In the home the bacteria can spread via contaminated cooking areas. Carriers and household pets, especially pet reptiles, can also spread the disease. Symptoms arise 6 to 72 hours after exposure and include severe diarrhea, fever and chills, vomiting, and abdominal cramps. Symptoms usually last three to five days.









sarcoma

highly malignant tumor arising in connective- and muscle-cell tissue. It is the result of oncogenes (the cancer causing genes of some viruses) and proto-oncogenes (cancer causing genes in human cells). It may affect bone, cartilage, blood vessels, lymph nodes, and skin.










SARS

SARS or severe acute respiratory syndrome is a communicable viral disease that can progress to a potentially fatal pneumonia. The first symptoms of SARS are usually a high fever, headache and body aches, sore throat, and mild respiratory symptoms; diarrhea may occur. A dry cough and shortness of breath typically develop two to seven days after the first symptoms, and in most persons pneumonia develops in a lobe of the lungs. In 10%–20% of all patients, the pneumonia spreads to other lobes, and death occurs in about 9% of all cases. The death rate is higher among older persons. There is no vaccine or treatment for the virus that causes the disease.

SARS is caused by a coronavirus, one of a group of viruses that are responsible for about one third of all cases of the common cold. The variety that causes SARS had not been previously identified, and may have been transmitted to humans from a civet species in whose blood the virus is also found. Civets are considered a delicacy in SE China, where the disease originated. Infection with SARS mainly occurs when a person in close contact with someone who has the disease is exposed to exhaled droplets. The spread of the disease has been controlled by isolating infected patients and quarantining those exposed to them.

The disease apparently first occurred in Nov., 2002, in Foshan, Guangdong prov., China, but provincial authorities withheld information about it, and when it spread to Beijing local authorities there acted similarly. In Feb., 2003, the World Health Organization first noted reports of cases of atypical pneumonia from China, but Chinese officials did not begin cooperating fully with international experts until April. SARS subsequently spread to some 30 countries on five continents, and affected the economies of China, Hong Kong, and Toronto, where cases were the highest; Taiwan and Singapore were also hard hit. The rapid international spread of the 2002–3 outbreak was facilitated by air travel and the lack of prompt, early information about SARS from Chinese officials.










starvation

condition in which deprivation of food has forced the body to feed on itself. Causes are famine, fasting, malnutrition, or abnormalities of the mucosal lining of the digestive system. Famines are often compounded by political strifes that restrict the distribution of aid and imports, as has been demonstrated in Ethiopia, Somalia, Iraq after the Persian Gulf War, and the conflict between the Serbs and Croats in former Yugoslavia. Fasting, usually conducted as a religious discipline or political protest, results in dizziness, weakness, and loss of bone mass; these lead to malnutrition. First to be lost are fat deposits and large quantities of water. The liver, spleen, and muscle tissue then suffer the greatest loss of weight. The heart and brain show little loss proportionately. The starving person becomes weak and lethargic. Body temperature, pulse rate, blood pressure, and basal metabolism continue to fall as starvation progresses, and death eventually ensues.












strabismus

inability of the eyes to focus together because of an imbalance in the muscles that control eye movement; also called squint. It is a consequence of weakness or uneven development of one or more of the six small muscles that surround the eye. One or both eyes may be affected. Horizontal strabismus is caused when the eyes do not move together laterally; this condition is known as cross-eye if the eye turns inward or walleye if the eye turns outward. Vertical strabismus results when the eye rolls upward or downward in its socket. There is also torsional strabismus in which the eyes do not rotate together about their optical axes. Strabismus is usually present at birth and becomes apparent early in infancy, but it may also result from illness or injury. Because the condition results in perception of a double image, there is a tendency to use only one eye. It is important that treatment be started as soon as possible to prevent loss of sight in the unused eye. Corrective therapy includes exercise that strengthens eye muscles and prescription of corrective lenses. Sometimes a patch is placed alternately on each eye so that neither is allowed to become completely unused. If necessary, the eye muscles may be shortened or lengthened surgically.









stroke

The destruction of brain tissue as a result of intracerebral hemorrhage or infarction caused by thrombosis (clotting) or embolus (obstruction in a blood vessel caused by clotted blood or other foreign matter circulating in the bloodstream); formerly called apoplexy. Cerebral hemorrhage or thrombosis occurs most often in elderly persons with constricted arteries, although either may also be caused by inflammatory or toxic damage to the cerebral blood vessels. Cerebral embolism may occur at any age, even in children.

Symptoms of stroke develop suddenly. In cases of severe brain damage there may be deep coma, paralysis of one side of the body, and loss of speech, followed by death or permanent neurological disturbances after recovery. If the brain damage sustained has been slight, there is usually complete recovery, but most survivors of stroke require extensive rehabilitation. Hypertension, which is a major cause of intracranial hemorrhage and stroke, can be treated by preventive measures using diet (e.g., increasing nutrients such as antioxidants and folate), drug therapy, and stress reduction techniques. Other preventive measures for people at high risk include daily aspirin to retard clot formation and surgical correction of the narrowed carotid artery. Sometimes surgical removal of the clot is possible on larger vessels, but it is usually pointless after the stroke or when blockage is widespread. The thrombolytic drug tissue plasminogen activator, widely used to treat heart attacks, has been approved for use within three hours of the onset of strokes caused by clots.







sty

in medicine terms, acute localized infection of one or more of the glands of the eyelid, with pain, swelling, and redness of the lid margin, usually caused by a staphylococcus infection. An external sty usually releases its pus and disappears in a day or so. Hot or cold compresses and antibiotic ointments are used to treat sties. Recurring sties are usually due to uncorrected refractive errors, poor general health, or infection elsewhere in the body. If a sty does not disappear in a few days, a physician should be consulted.










scabies

highly contagious parasitic skin disease caused by the itch mite (Sarcoptes scabiei). The disease is also known as itch. It is acquired through close contact with an infested individual or contaminated clothing and is most prevalent among those living in crowded and unhygienic conditions. The female mite burrows her way into the skin, depositing eggs along the tunnel. The larvae hatch in several days and find their way into the hair follicles. Itching is most intense at night because of the nocturnal activity of the parasites. Aside from the burrows, which are usually clearly visible, there are a variety of skin lesions, many of them brought on by scratching and infection. All clothing and bedding of the victim and his household should be disinfected. Disinfestation of the skin is accomplished by applying creams or ointments containing gamma benzene hexachloride or benzyl benzoate. A variety of S. scabiei causes mange in animals.











scar

fibrous connective tissue that forms at the site of injury or disease in any tissue of the body. Scar tissue may replace injured skin and underlying muscle, damaged heart muscle, or diseased areas of internal organs such as the liver. Dense and thick, it is usually paler than the surrounding tissue because it is poorly supplied with blood, and although it structurally replaces destroyed tissue, it cannot perform the functions of the missing tissue. Scar tissue may therefore limit the range of muscle movement or prevent proper circulation of fluids when affecting the lymphatic or circulatory system. Extensively scarred tissue may lose its ability to function normally.










to be continued

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scarlet fever

scarlet fever or scarlatina,an acute, communicable infection, caused by group A hemolytic streptococcal bacteria that produce an erythrogenic toxin. The disease is now uncommon, probably because antibiotic therapy has lessened the likelihood of spread. It occurs in young children, usually between two and eight years of age, and is spread by droplet spray from carriers and from individuals who have contracted the disease. The incubation period is from three to five days, and infectivity lasts about two weeks. Scarlet fever may be mild or severe, but it is rarely fatal if treated. Typical symptoms are sore throat, headache, fever, flushed face with a ring of pallor about the mouth, red spots in the mouth, coated tongue with raw beefy appearance and inflamed papillae underneath it (strawberry tongue), and a characteristic eruption on the body. The streptococcal bacterium that causes scarlet fever is identical to the streptococcal pharyngitis (strep throat) organism, the difference being the production of a toxin to which the patient is susceptible in the case of scarlet fever. Severe infections are occasionally complicated by rheumatic fever, kidney disease, ear infection, pneumonia, meningitis, or encephalitis. Mild scarlet fever requires only bed rest, antibiotics, analgesics or antipyretics, and symptomatic treatment. Antibiotics, immune serum, and antitoxin may be required for severe cases.









schistosomiasis

schistosomiasis OR bilharziasis,or snail fever,parasitic disease caused by blood flukes, trematode worms of the genus Schistosoma. Three species are human parasites: S. mansoni, S. japonicum, and S. haematobium. The disease is prevalent in Asia, some Pacific islands, Africa, the West Indies, South America, Spain, Puerto Rico, and Cyprus. The larvae of the parasite are harbored by snails, which serve as intermediate hosts, and infect humans who bathe in or otherwise come in contact with infested waters. The larvae enter through the skin, migrate via the blood vessels, and mature in the lungs. From there they travel to the veins of the upper or lower intestine or bladder and reproduce. Some eggs pass out in the feces. Others are carried into the liver, where the body surrounds them with white blood cells, forming hundreds of tiny ball-like granulomas that eventually impair the liver's ability to function. It is believed that the flukes settle in blood vessels that have a particular human immune substance, tumor necrosis factor, that they require in order to reproduce.

The disease is characterized by a skin eruption at the site of entry, fever, diarrhea, and other symptoms, depending on the tissues affected; cirrhosis of the liver is common. The disease can be cured with the drug praziquantel, but reinfection can occur. Although symptoms vary according to the species of infecting fluke, all forms can result in general weakening and eventual death. Control of the disease is difficult, but attempts have been made to eradicate the snail hosts. Proper sanitation and disposal of human wastes are also important.










sciatica

severe pain in the leg along the sciatic nerve and its branches. It may be caused by injury or pressure to the base of the nerve in the lower back, or by metabolic, toxic, or infectious disease. Treatment is for the underlying condition; measures for the relief of pain include bed rest, immobilization of the leg, heat, and sedation.








scurvy

deficiency disorder resulting from a lack of vitamin C (ascorbic acid) in the diet. Scurvy does not occur in most animals because they can synthesize their own vitamin C, but humans, other primates, guinea pigs, and a few other species lack an enzyme necessary for such synthesis and must obtain vitamin C through their diet. Vitamin C is widespread in plant tissues, with particularly high concentrations occurring in citrus fruits (oranges, lemons, limes, grapefruits); tomatoes, potatoes, cabbages, and green peppers are also good sources of this vitamin.

Scurvy results in the weakening of capillaries, which causes hemorrhages into the tissues, bleeding of the gums, loosening of the teeth, anemia, and general debility. In infants there is also interference with bone development. Severe phases of the disorder can result in death. Scurvy is treated with large doses of vitamin C. Modern methods of transporting and preserving foods have made a diet rich in vitamin C available everywhere throughout the year, and even infants' diets include orange juice. Vitamin C is also available in tablet or syrup form.

Scurvy was a serious problem in the past, when fresh fruits and vegetables were not available during the winter in many parts of the world. It was especially common among sailors in the days when only nonperishable foods could be stocked aboard ship. More than half the crew of Vasco da Gama died from scurvy on his first trip (1497–99) around the Cape of Good Hope. In 1747 the Scottish naval surgeon James Lind treated scurvy-ridden sailors with lemons and oranges and obtained dramatic cures. In 1795 the British navy began to distribute regular rations of lime juice during long sea voyages (hence the name limeys for British sailors), a measure that was largely successful in preventing scurvy. It was probably the first disease to be definitely associated with a dietary deficiency.











serum sickness

hypersensitive response that occurs after injection of a large amount of foreign protein. The condition is named for the serum taken from horses or other animals immunized against a particular disease, e.g., tetanus or diphtheria. Such serum, which contains antibodies against the disease toxins, was formerly widely used to temporarily immunize humans. However, the antibodies from the animal serum are also foreign proteins that can act as antigens when injected into humans. The recipient's body responds by producing, within 8 to 12 days, antibodies that react against the animal serum proteins; the reaction causes injury to blood vessel walls and such allergic symptoms as rash, itching, and swelling of the lymph nodes. Fever, joint pain, spleen enlargement, and even shock may occur. The reaction subsides as continued production of antibodies removes foreign protein from circulation. A person who has once had a serum injection is sensitized to the serum antigens, and a second injection can bring on the acute reactions typical of anaphylaxis. Today, serum preparations are rarely used. Instead, inoculations of tetanus and diphtheria toxoids are given in childhood; they confer active immunity against those diseases. Serum sickness may occur in response to proteins other than those found in serum.











senility

deterioration of body and mind associated with old age. Indications of old age vary in the time of their appearance. Stooped posture, wrinkled skin, decrease in muscle strength, changes in the lens and muscles of the eye, brittleness of bone and stiffness of the joints, and hardening of the arteries (arteriosclerosis) are among the physical changes associated with old age. The mental changes associated with senility include impairment of judgment, loss of memory, and sometimes childish behavior. The psychological changes are thought to be related to aging of the cortical brain cells. Whereas the physical changes associated with aging occur in all individuals to some extent, evidence of psychological degeneration is not universal. In common usage, the term senility is applied only to mental deterioration.









septicemia

invasion of the bloodstream by virulent bacteria that multiply and discharge their toxic products. The disorder, which is serious and sometimes fatal, is commonly known as blood poisoning. The invasive organisms are usually streptococci or staphylococci but may be any type of bacteria. Septicemia occurs most often in older people who have underlying disease that makes them more susceptible to the infection. The primary causes of septicemia are infection within the walls of the blood vessels, rapidly progressing tissue infections (osteomyelitis, cellulitis), virulent systemic disease (meningitis, typhoid), and local infections (abscess, carbuncle) that the defense mechanisms of the body are unable to contain. The microorganisms usually spread to other organs, such as the lungs, liver, and brain.

Symptoms of septicemia are fever (usually quite high), chills, low blood pressure, confusion, and rash; it often results in multiple organ failure if not treated promptly with antibiotics. The diagnosis can be confirmed with blood cultures for the organism or with blood tests for antibodies or high levels of white blood cells.








shock

any condition in which the circulatory system is unable to provide adequate circulation to the body tissues, also called circulatory failure or circulatory collapse. Shock results in the slowing of vital functions and in severe cases, if untreated, in death. It may be caused by inadequate pumping by the heart, by reduction of the blood volume due to dehydration or to loss of blood or plasma, or by reduced blood pressure resulting from dilation of the blood vessels. Inadequate pumping may occur as a result of various kinds of heart disease. Blood loss may result from injuries or from such internal conditions as bleeding ulcers. Burns produce extensive plasma loss from blood vessels into the burned area; crush injuries may result in loss of blood and plasma into the injured tissues. Dilation of blood vessels may be caused by injury to the nervous system, or by pain or emotional stress. Fainting is a form of shock brought about by a sudden reduction of the blood supply to the brain. Symptoms of shock include weakness, pallor, cold and moist skin, and thirst. The arterial blood pressure is reduced, the pulse is weak and rapid, and the surface veins of the limbs may collapse. Emergency aid for shock victims includes maintaining a clear breathing passage, administering oxygen, controlling bleeding, and keeping the patient warm and in a supine position with legs elevated. Therapy may include blood or plasma transfusion to restore the normal circulation, as well as treatment of the underlying cause of shock. The term shock is also applied to a variety of other conditions such as electric shock, allergic shock, and emotional shock.










Siamese twins

congenitally united organisms that are complete or nearly complete individuals. They develop from a single fertilized ovum that has divided imperfectly; complete division would produce identical twins, having the same sex and general characteristics. Siamese twins remain attached at the abdomen, chest, back, or top of the head, depending on where the division of the ovum has failed. In some instances the individuals are joined only by a band of musculofibrous tissue and can be separated surgically, but in other instances they share vital organs and separation may not be possible. Sometimes an ovum divides in such a way that an organism develops having one body and two heads, or one head and two sets of limbs; such organisms are known as monsters. Only rarely do Siamese twins survive birth. When they do, fatal illness in one dooms the other unless separation is possible. The name Siamese twins derives from the most famous of conjoined male twins, Chang and Eng, born in Siam of Chinese parents in 1811. They were exhibited in Barnum's circus for many years; although never separated, they married and fathered a total of 22 children. They died within 2 hours of each other in 1874.








sickle cell disease

sickle cell disease or sickle cell anemia,inherited disorder of the blood in which the oxygen-carrying hemoglobin pigment in erythrocytes (red blood cells) is abnormal. This “hemoglobin-S” crystallizes in small capillaries, where the concentration of oxygen in the blood is low (but sufficient for normal hemoglobin), causing the red blood cells to assume distorted, sicklelike shapes. Linus Pauling discovered the chemical abnormality of the hemoglobin molecule that causes the erythrocyte sickling in 1949.

The sickled red blood cells tend to clog small blood vessels, depriving the tissues they serve of blood and oxygen. Painful “crises” result, with symptoms depending on the site affected (e.g., joint and abdominal pain or kidney damage). Strokes or seizures can occur if the brain is affected. Lung infections resulting from the patient's disinclination to take painful deep breaths are a frequent complication. In addition, the sickled erythrocytes are fragile and subject to rupture and destruction, leading to hemolytic anemia (reduction of oxygen-carrying hemoglobin caused by premature destruction of red blood cells) and such symptoms as fatigue, jaundice, and headaches.


Treatment

There is no cure for the disease, but advancements in treatment have improved median survival to 42 years for men and 48 years for women. Cerebral hemorrhage or shock is the usual cause of mortality in children. Recent studies have indicated that regular blood transfusions can prevent strokes in children. Anemia is treated with folic acid. Sickle cell crises may be treated with intravenous hydration, pain medication, antibiotics, oxygen, and transfusions. Hydroxyurea, formerly used as a cancer treatment, has been helpful to many adults with the disease, lessening the frequency and severity of crises. New drugs for reducing the severity of crises are being tested as well. One acts as a lubricant, allowing sickled cells to flow more easily through tiny vessels. The other helps to prevent tissue deprived of blood from dying during a crisis.


Incidence

The disease is confined mainly to blacks, especially those of W African descent, but it also occurs in persons of Mediterranean, Middle Eastern, and Indian origin. The mutation may at one time have had an advantageous effect; those afflicted with the abnormality have a higher survival rate in malaria-infested zones.

Under normal circumstances the disease occurs only in those patients who inherit the gene for the abnormal hemoglobin from both parents. This so-called homozygous form of the disease occurs in 1 in 400 African Americans. About 8% of African Americans have sickle cell trait; that is, they are heterozygotes, usually symptomless carriers who have inherited a normal hemoglobin gene from one parent and hemoglobin-S from the other. There are also intermediate forms of the disease that result when a gene for hemoglobin-S is inherited from one parent and a gene for any of several other abnormal kinds of hemoglobin is inherited from the other. Genetic screening is recommended for prospective parents at risk of passing on the disease. If both parents are carriers (i.e., have sickle cell trait), then each child has a one in four chance of having sickle cell disease.











silicosis

occupational disease of the lungs caused by inhalation of free silica (quartz) dust over a prolonged period of time. Free silica is dispersed in the air and inhaled by workers engaged in the mining of lead, hard coal, and gold, in cutting sandstone and granite, in sandblasting, and in the manufacture of silica abrasives. The irritative action of the silica in the lung results in the formation of nodular lesions; these may coalesce and form massive areas of fibrous tissue. In advanced cases patients experience difficult breathing, coughing with sputum, chest pain, and a tendency to develop tuberculosis or repeated attacks of pneumonia. Once fibrosis has developed there is no cure, and treatment is directed at the management of symptoms. Preventive measures adopted in industries where the hazard of silicosis exists have greatly reduced its incidence.











skin cancer

malignant tumor of the skin. The most common types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Rarer forms include mycosis fungoides (a type of lymphoma) and Kaposi's sarcoma. Overexposure to the sun is the primary cause of the common skin cancers, and the popularity of tanning since the 1930s lies behind the rise in skin cancer rates. The depletion of the earth's protective ozone layer also plays a role. The most effective way of preventing skin cancer is to avoid exposure to the sun's ultraviolet rays by consistently applying effective sunscreens (see sunburn) and wearing protective clothing.


Basal and Squamous Cell Carcinomas

Basal and squamous cell carcinomas are the most common types of cancer. Both arise from epithelial tissue. They are rare in dark-skinned people; light-skinned, blue-eyed people who do not tan well but who have had significant exposure to the rays of the sun are at highest risk. Both types usually occur on the face or other exposed areas.

Basal cell carcinoma typically is seen as a raised, sometimes ulcerous nodule. The nodule may have a pearly appearance. It grows slowly and rarely metastasizes (spreads), but it can be locally destructive and disfiguring. Squamous cell carcinoma typically is seen as a painless lump that grows into a wartlike lesion, or it may arise in patches of red, scaly sun-damaged skin called actinic keratoses. It can metastasize and can lead to death.

Basal and squamous cell carcinomas are easily cured with appropriate treatment. The lesion is usually removed by scalpal excision, curettage, cryosurgery (freezing), or micrographic surgery in which successive thin slices are removed and examined for cancerous cells under a microscope until the samples are clear. If the cancer arises in an area where surgery would be difficult or disfiguring, radiation therapy may be employed. Genetic scientists have discovered a gene that, when mutated, causes basal cell carcinoma.


Melanoma

Melanoma is the most virulent type of skin cancer and the type most likely to be fatal. As with the other common skin cancers, melanoma can be caused by exposure to the sun, and its incidence is increasing around the world. There also appears to be a hereditary factor in some cases. Although light-skinned people are the most susceptible, melanomas are also seen in dark-skinned people. Melanomas arise in melanocytes, the melanin-containing cells of the epidermal layer of the skin. Melanin is the pigment that gives skin color and that helps to protect the skin from sun damage. In light-skinned people, melanomas appear most frequently on the trunk in men and on the arms or legs in women. In blacks melanomas appear most frequently on the hands and feet. It is unknown whether melanoma in blacks is related to sun exposure. It is recommended that people examine themselves regularly for any evidence of the characteristic changes in a mole that could raise a suspicion of melanoma. These include asymmetry of the mole, a mottled appearance (variations in color from shades of brown to a bluish tint), irregular or notched borders, and oozing or bleeding or a change in texture. Surgery performed before the melanoma has spread is the only effective treatment for melanoma.











to be continued

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sleep apnea

episodes of interrupted breathing during sleep. Obstructive sleep apnea is a common disorder in which relaxation of muscles in the throat repeatedly close off the airway during sleep; the person wakes just enough to take a gasping breath. This process is repeated many times during sleep and usually is not remembered the next day. Those suffering from severe obstructive sleep apnea typically complain of sleepiness, irritability, forgetfulness, and difficulty in concentrating. They may have difficulties in their occupational or social lives and be prone to motor vehicle accidents.

Most people with obstructive sleep apnea tend to be obese and snore loudly. The disorder has been medically linked to hypertension, which in turn puts people at greater risk of heart failure and stroke. Weight reduction in persons who are overweight is an important factor in effective treatment. Alcoholic drinks near bedtime and sleeping pills should be avoided. Sometimes obstructive sleep apnea can be treated by surgically correcting the narrowing of the airway. Another option is continuous positive airway pressure, which involves wearing a mask over the nose and mouth during sleep; this treatment keeps the airway open by forcing air into the nasal passages. A different type of sleep apnea, called central sleep apnea, is believed to be caused by an abnormality in the brain's regulation of breathing during sleep.








slow virus

technically a virus, such as a lentivirus, that causes symptoms in an infected host long after the original infection and progresses slowly. Although many viruses fit this description, the term slow virus is usually reserved for the first recognized lentiviruses, such as the virus that causes visna (a disease of sheep). A slow virus was proposed as a cause for those diseases now generally recognized as prion diseases (e.g., Creutzfeld-Jacob disease and scrapie).











slipped disc

rupture or herniation of an intervertebral disc. These discs separate and cushion the vertebrae, the segments of the spinal column. They are composed of an outer rim of fibrous connective tissue and a gelatinlike inner core. If the fibrous rim breaks the core may leak into the spinal canal, resulting in severe pain that is aggravated by bending, straining, or coughing. Material from the disc may press on spinal nerves and cause numbness or tingling, weakness, or paralysis in the area of the body enervated by those nerves. Slipped discs occur as a result of severe strain or without any apparent stress at all. They are most common in the lower back and neck. Treatment consists of bed rest, usually with a hard board placed beneath the mattress, local application of heat, and the administration of muscle relaxants to relieve spasms. If natural healing fails to occur surgery may be required to remove the disc, and the affected vertebrae fused to keep them from rubbing together.







smallpox

acute & highly contagious disease causing a high fever and successive stages of severe skin eruptions. The disease dates from the time of ancient Egypt or before. It has occurred worldwide in epidemics throughout history, killing up to 40% of those who contracted it and accounting for more deaths over time than any other infectious disease. Spreading to the New World with European colonization, it killed huge numbers of the indigenous people, who had no immunity, greatly contributing to the annihilation of native cultures.

Smallpox is caused by a virus that may be airborne or spread by direct contact. After an incubation period of about two weeks, fever, aching, and prostration occur, lasting two or three days. An eruption then appears and spreads over the entire body; the lesions become blisterlike and pustular within a week. The lesions then open and crust over, causing itching and pain. When the crusts fall off, usually in another one or two weeks, the extent of permanent damage to the skin (pockmarks) becomes evident. There is no specific treatment for smallpox; an antibiotic may be administered to prevent secondary bacterial infection.

A crude vaccination method began with Emanuel Timoni, a Greek physician, in the early 18th cent. Edward Jenner modified the procedure (1796) by using the related cowpox virus to confer immunity. By 1977, vaccination programs, such as those by the World Health Organization (WHO), had eliminated the disease worldwide.

After 1980, when WHO officially declared smallpox eradicated as a disease, scientists retained some samples of the virus in laboratories for study. They mapped the genetic sequence of three strains of smallpox, and the destruction of the remaining samples of the live virus was scheduled and postponed several times. Owing to fears of a new natural outbreak or of the potential use of smallpox as a terrorist weapon against populations no longer vaccinated, research with the virus continued. The last declared samples of live virus are now stored by the U.S. and Russian governments under strict security, but it is believed that some nations may have secret stores of the virus that they could use as biological weapons. Responding to these concerns, WHO postponed the scheduled 1999 destruction of all remaining stocks of the smallpox virus until 2002. The 2001 bioterror attacks in the United States with anthrax led the United States and other nations to stockpile doses of smallpox vaccine out of concern that the smallpox virus might be used by terrorists, and WHO agreed to delay the destruction of virus stocks beyond 2002 to allow for the development of new vaccines. In 2002, because of bioterrorism concerns, the G. W. Bush administration decided to vaccinate frontline military personnel and health-care and emergency workers against smallpox.








smoking

inhalation and exhalation of the fumes of burning tobacco in cigars and cigarettes and pipes. Some persons draw the smoke into their lungs; others do not. Smoking was probably first practiced by the indigenous peoples of the Western Hemisphere. Originally used in religious rituals, and in some instances for medicinal purposes, smoking and the use of tobacco became a widespread practice by the late 1500s. Tobacco was introduced into Europe by the explorers of the New World; however, many rulers prohibited its use and penalized offenders. By the end of the 19th cent. mass production of cigarettes had begun, and the smoking of cigarettes became prevalent as the use of cigars and pipes declined. Despite controversy as to the effects of smoking and bans on smoking by certain religious groups, the use of tobacco continued to increase.


Health Effects

Smoking is considered a health hazard because tobacco smoke contains nicotine, a poisonous alkaloid, and other harmful substances such as carbon monoxide, acrolein, ammonia, prussic acid, and a number of aldehydes and tars; in all tobacco contains some 4,000 chemicals. In 1964 definitive proof that cigarette smoking is a serious health hazard was contained in a report by the Surgeon General's Advisory Committee on Health, appointed by the U.S. Public Health Service. The committee drew evidence from numerous studies conducted over decades. They concluded that a smoker has a significantly greater chance of contracting lung cancer than a nonsmoker, the rate varying according to factors such as the number of cigarettes smoked per day, the number of years the subject smoked, and the time in the person's life when he or she began smoking. Cigarette smoking was also found to be an important cause of cancers of the esophagus, nasopharynx, mouth, larynx, kidney, and bladder as well as a cause of chronic obstructive pulmonary disease, emphysema, and heart disease, stroke, and other cardiovascular diseases. Since then it has been found to be an independent risk factor in male impotence. Smoking also increases risks associated with oral contraceptive use and exposure to occupational hazards, such as asbestos. Pipe and cigar smokers, if they do not inhale, are not as prone to lung cancer as cigarette smokers, but they are as likely to develop cancers of the mouth, larynx, and esophagus. Those who use snuff or chewing tobacco (sometimes called “smokeless tobacco”) run a greater risk of developing cancer of the mouth.

Inhalation of tobacco smoke by nonsmokers has been found to increase the risk of heart disease and respiratory problems; this has created a movement for smokeless environments in public spaces, including government buildings, office buildings, and restaurants. Fetal damage can be caused if a mother smokes or is exposed to smoke during pregnancy. Children of smokers have a higher risk of asthma and lung disease.



Regulation of Smoking

Because of mounting evidence of health risks, television advertisements for cigarettes were banned beginning in 1971. In the 1980s, Congress began to require stronger warning labels on all print advertising; soon afterward it banned smoking on domestic air flights. A 1988 report of the Surgeon General of the United States recognized nicotine as an addictive substance, leading the Food and Drug Administration (FDA) to consider treating nicotine as any other addictive drug and implementing stricter regulations. The authority of the FDA to regulate smoking was, however, denied by the Supreme Court. The habit of smoking continues to increase in the young despite the illegality of cigarette sales to those under 18 years of age in all 50 states.

The Framework Convention on Tobacco Control, a treaty adopted by World Health Organization members in 2003, will establish international standards for antismoking measures once it is ratified. The convention creates restrictions on the marketing and sale of tobacco products and require health warnings on packages of cigarettes. Indoor air quality laws, high taxes on tobacco, and meansures against cigarette smuggling are encouraged under the pact.


Legal Battles

In the mid- and late 1990s the tobacco industry in the United States faced grave legal and financial threats. Under heavy attack from states seeking compensation to recover costs for smoking-related health care, from the federal government seeking further regulation, and from individual smokers seeking damages for illness, the major cigarette producers sought ways to protect themselves. After a tentative $368 billion settlement (1997) with state attorneys and plaintiffs' lawyers fell apart, lawsuits were brought against the industry by Florida, Minnesota, Mississippi, and Texas; the suits were settled for $40 billion, to be paid over 25 years. In 1998 the remaining 46 states accepted a $206 billion plan to settle lawsuits they had filed against the industry. Individual lawsuits continued to pose potential significant financial threats. The Framework Convention on Tobacco Control, which came into affect in 2005 and has been ratified by more than 55 nations, seeks to reduce the number of tobacco-related illnesses and deaths by such measures as banning tobacco product advertising and putting warning labels on tobacco packaging. The treaty has been signed, but not ratified, by the United States.








snakebite

wound inflicted by the teeth of a snake. The bite of a nonvenomous snake is rarely serious. Venomous snakes have fangs, hollow teeth through which poison is injected into a victim. All types of snake venom contain a toxin that affects the nerves and tends to paralyze the victim. In addition, the venom of the coral snake, the cobra, and the South American rattlesnake contains constituents that damage blood cells and dissolve the linings of the blood vessels and the lymphatic vessels, causing severe or fatal internal hemorrhage and collapse. First aid for venomous snakebites consists of retarding the spread of the poison through the circulatory system by applying a constricting band or an ice pack, or by spraying ethyl chloride on the wound. It is essential that the patient avoid exertion and the taking of stimulants, as both increase the pulse rate. The constricting band should be applied above the swelling caused by the wound; it should be tight, but not tight enough to stop the pulsing of the blood. If only a few minutes have passed since the infliction of the bite, it is possible to remove much of the poison by suction. Antivenins, which counteract the toxins, are available for most types of snake venom. The two main groups of poisonous snakes in the United States are the coral snakes, which rarely attack humans unless provoked, and the pit vipers (copperhead, cottonmouth moccasin, the various rattlers), which require no provocation.









sneeze

involuntary violent expiration of air through the nose and mouth. It results from stimulation of the nervous system in the nose, causing sudden contraction of the muscles of expiration. The stimulus can include any irritating factor in the nose—inflammation of the tissues as the result of a cold or infection, allergic irritants (hay fever), or irritating substances such as dust or pollutants in the air. An occasional sneeze usually has little significance. Repeated sneezing indicates that some condition of the nose or in the immediate atmosphere requires attention.







snoring

rough & vibratory sounds made in breathing during sleep or coma. The noisy breathing is the result of an open mouth and a relaxation of the palate; it is frequently induced by lying on one's back. Snoring may indicate some obstruction to nasal breathing such as enlarged adenoids; this is especially true in children. In some individuals it is merely a poor breathing habit and usually disappears when the person lies on his side.










streptococcal sore throat

infection and inflammation of the pharynx caused by certain streptococcal bacteria. These organisms are known as hemolytic streptococci because they secrete toxins that dissolve, or cause hemolysis of, red blood cells. Acute streptococcal sore throat is usually characterized by an extremely painful throat, enlarged tonsils, and sometimes gastrointestinal disturbances. Scarlet fever, which is caused by the same streptococcal bacteria, occurs when the microorganisms produce a toxin that, in sensitive individuals, causes appearance of a characteristic rash. Complications of streptococcal infection, which include rheumatic fever and sometimes arthritis and nephritis, can be prevented by early, vigorous treatment with penicillin or other suitable antibiotics.








spasm

involuntary rigid muscle contraction, often persistent and often accompanied by pain. It usually has some underlying physical cause such as disease, strain, or injury to the muscle or nearby tissues, impairment of circulation, or a disturbance of body chemistry. The spasm may be confined to one group of muscles or it may be severe and fairly generalized, as in convulsions. Painless localized spasms are called tics. These purposeless movements, usually of some part of the face, may begin as purposeful movement in response to some stimulus but eventually are carried out automatically, apparently without reason. They may disappear spontaneously after a time, or may require the elimination of some physical or psychic cause.






spastic paralysis

form of paralysis in which the part of the nervous system that controls coordinated movement of the voluntary muscles is disabled. In spastic paralysis the nerves controlling muscle movement are hyperirritable and do not function in a coordinated manner, so that impulses from them cause spasmodic muscle contraction. Extreme spastic paralysis occurs after various kinds of brain damage, e.g., stroke. Spinal cord injury, such as that produced by inflammatory diseases of nerve tissue, can injure motor neuron fibers in the spine and cause spastic paralysis. Congenital spastic paralysis, or cerebral palsy, is often a result of intrauterine disease or birth injury, or occasionally some inherited nervous system defect.







speech defect

any condition that interferes with the mental formation of words or their physical production. Speech defects in children generally become apparent in the early school years. Speech problems may arise from organic or functional abnormalities, but in practice the two are often hard to differentiate. Organic defects include deafness, cleft palate, dental abnormalities, and brain damage; most functional problems are basically psychological. Speech defects are generally categorized as disorders of sound production; disorders of voicing, e.g., loudness, pitch, and quality deviations; disorders of rhythm, such as stuttering and stammering; and disorders of language formulation and expression, including aphasia, the inability to use words as symbols of ideas. Treatment of a speech defect may include correction of organic conditions, psychotherapy, and training in proper articulation; it is rarely limited to a single type of therapy









sprain

stretching or wrenching of the ligaments and tendons of a joint, often with rupture of the tissues but without dislocation. Sprains occur most commonly at the ankle, knee, or wrist joints, causing pain, swelling, and difficulty in moving the involved joint. Treatment consists of application of ice bags or cold compresses, elevation of the injured part, and strapping or bandaging to substitute for the support usually given by the ligaments. A severe ankle sprain may require a cast to immobilize the joint for healing.







sprue

chronic disorder of the small intestine caused by impaired absorption of fat and other nutrients. Two forms of the disease exist. Tropical sprue occurs in central and northern South America, Asia, Africa, and other specific locations. No cause has been identified, but suggested causes include infection, parasitic infestation, vitamin deficiency, and food toxin. Tropical sprue responds to antibiotic and folic acid therapy. Nontropical sprue, also called celiac disease, is primarily a disease of young children and usually begins between the ages of 6 and 18 months. It is a hereditary congenital disorder caused by a sensitivity to the gliadin fraction of gluten, a cereal protein. Nontropical sprue can be fatal, particularly if growth abnormalities are ignored or unrecognized. It is not known if scrupulous adherence in this disease decreases the likelihood of intestinal lymphoma, but the deletion of gluten from the diet and the intake of vitamin, mineral, and hematinic supplements facilitate remission. Steroid treatments are often used if a gluten-free diet is ineffective; if steroid treatment is ineffective the prognosis is not good. The symptoms of both types of sprue are generally the same: diarrhea with bulky, frothy, foul-smelling stools containing large amounts of fatty acids and soaps, and later weight loss, anemia, and other symptoms related to malabsorption of vitamins. X-ray examination of the small intestine revealing dilation, segmentation, and other typical changes is used in diagnosis.








sudden infant death syndrome

sudden infant death syndrome (SIDS) or crib death,sudden, unexpected, and unexplained death of an apparently healthy infant under one year of age (usually between two weeks and eight months old). SIDS accounts for 10% of infant deaths and is the second highest cause of death (after accidents) in infancy. The risk is higher in males, in low-birth-weight infants, in lower socioeconomic levels, during cold months, and for babies who sleep face down.

Causal theories suggest that the infant may have immature or hypersensitive lungs, may have a defect in brain-stem control of breathing, or may be rebreathing carbon dioxide. Recent studies have shown persistent high levels of an infant form of hemoglobin in babies with known risk factors for the condition.

SIDS victims are thought to have brief episodes of apnea (breathing stoppage) before the fatal one. An alarm system that detects breathing abnormalities is sometimes used with infants suspected of being prone to SIDS. The American Academy of Pediatrics has recommended that babies be laid to sleep on their backs or sides.









sunburn

inflammation of the skin caused by actinic rays from the sun or artificial sources. Moderate exposure to ultraviolet radiation is followed by a red blush, but severe exposure may result in blisters, pain, and constitutional symptoms. As ultraviolet rays penetrate the skin, they break down collagen and elastin, the two main structural components of the skin, a process that results in the wrinkled appearance of sun-damaged skin. In addition, the sun damages the DNA of the exposed skin cells. In response, the cells release enzymes that excise the damaged parts of the DNA and encourage the production of replacement DNA (a process that can go wrong and result in skin cancer). At the same time, the production of melanin increases, darkening the skin. Melanin, the pigment that gives skin its color, acts as a barrier to further damage by absorbing ultraviolet light. A suntan. results from this attempt by the skin to protect itself. Light-skinned persons and infants are especially susceptible to ultraviolet rays because they lack sufficient protective skin pigment. Certain diseases and drugs may also increase photosensitivity.

Due to the increase in the incidence of skin cancer and the effects of ozone layer depletion, more attention is being placed on protecting the skin from the sun's ultraviolet rays with broad spectrum sunscreens or clothing. Broad spectrum sunscreens block both UVA and UVB rays (two of the three bands of ultraviolet radiation). The relative UVB protection of a sunscreen is indicated by its SPF (sun protection factor) number; a higher number indicates a more effective sunscreen. Some products may contain opaque formulations of zinc oxide or titanium dioxide that physically block all rays.

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T

tapeworm

name for the parasitic flatworms forming the class Cestoda. All tapeworms spend the adult phase of their lives as parasites in the gut of a vertebrate animal (called the primary host). Most tapeworms spend part of their life cycle in the tissues of one or more other animals (called intermediate hosts), which may be vertebrates or arthropods.


Anatomy and Function

An adult tapeworm consists of a knoblike head, or scolex, equipped with hooks for attaching to the intestinal wall of the host (which may be a human), a neck region, and a series of flat, rectangular body segments, or proglottids, generated by the neck. The chain of proglottids may reach a length of 15 or 20 ft (4.6–6.1 m). Terminal proglottids break off and are excreted in the feces of the host, but new ones are constantly formed at the anterior end of the worm. As long as the scolex and neck are intact the worm is alive and capable of growth. A rudimentary nervous system and excretory system run the length of the worm, through the proglottids. However, there is no digestive tract; the worm absorbs the host's digested food through its cuticle, or outer covering.


Reproduction

Each proglottid contains a complete set of male and female reproductive organs that produce the sex cells. Fertilization is internal; in most species cross fertilization between two adjacent worms is necessary, but in a few species self-fertilization may occur between two proglottids of the same worm, or within the same proglottid. In some species the fertilized eggs are shed continuously and leave the host's body in the feces; in others the fertilized eggs are stored until the proglottid is filled with them and the entire proglottid is then shed. The eggs develop into embryos with a hard outer shell; these do not hatch until they are eaten by a suitable intermediate host.


Humans as Tapeworm Hosts

Human tapeworm infestations are most common in regions where there is fecal contamination of soil and water and where meat and fish are eaten raw or lightly cooked. In the case of the human tapeworm most common in the United States (the beef tapeworm, Taenia saginata) the usual intermediate host is a cow, which ingests the proglottid while drinking or grazing. The round-bodied embryos, equipped with sharp hooks, hatch and bore through the cow's intestinal wall into the bloodstream, where they are carried to the muscles. Here each embryo encloses itself in a cyst, or bladder; at this stage it is called a bladder worm. During the bladder worm stage the embryo develops into a miniature scolex; it remains encysted until the muscle is eaten by a primary host, in this case a human. If the scolex has not been killed by sufficient cooking of the meat, it sheds its covering and attaches to the intestinal wall, where it begins producing proglottids.

A human tapeworm common in Mexico, the pork tapeworm (T. solium), has a similar life cycle, with a pig as the usual intermediate host. The fish tapeworm, Diphyllobothrium latum, transmitted to humans from fish, especially pike, is common in Asia and in Canada and the northern lake regions of the United States. This tapeworm has a more elaborate life cycle, involving both a fish and a crustacean as intermediate hosts. The dwarf tapeworm, Hymenolepsis nana, is transmitted through fecal contamination and is common in children in the southeastern United States. There are also several tapeworms for whom humans the usual intermediate host; among these, the dog tapeworm, Echinococcus granulosis, spends its adult phase in the intestines of dogs.


Consequences of Infestation

Intestinal tapeworm infestation frequently occurs without symptoms; occasionally there is abdominal discomfort, diarrhea, constipation, or weight loss. The presence of tapeworm proglottids in clothing, bedding, or feces is the usual sign of infestation. Treatment is with quinacrine hydrochloride (Atabrine) or niclosamide, which kill the worm.

The most serious tapeworm infestation in humans is caused by the ingestion of T. solanum eggs through fecal contamination, which results in the person serving as the intermediate, rather than the primary, host. The embryos migrate throughout the body, producing serious illness if they lodge in the central nervous system. The embryos of the dog tapeworm encyst in various internal organs of humans, most commonly in the liver. The cysts produced by these embryos are called hydatid cysts, and the infestation of the liver is called hydatid disease.















tartar, dental

precipitate of saliva that accumulates around teeth at the gum line. Composed primarily of calcium salts, tartar forms as a hard brownish substance that irritates gums and causes them to recede. Inflammation of this tissue may lead to the recession and infection of the bones in which teeth are imbedded and result in the loosening and loss of teeth. As symptoms may not become apparent until serious damage has occurred, periodic dental visits for the removal of tartar are recommended.










Tay-Sachs disease

rare hereditary disease caused by a genetic mutation that leaves the body unable to produce an enzyme necessary for fat metabolism in nerve cells, producing central nervous system degeneration. The disease is named for a British ophthalmologist, Warren Tay, who first described the disease, in 1881, and a New York neurologist, Bernard Sachs, who first described the cellular changes and the genetic nature of the disease, in 1887. In infants, it is characterized by progressive mental deterioration, blindness, paralysis, epileptic seizures, and death, usually between ages three and five. Late-onset Tay-Sachs occurs in persons who have a genetic mutation that is similar but allows some production of the missing enzyme. There is no treatment for Tay-Sachs.

Course of the Disease

The enzyme involved in Tay-Sachs is called hexosaminidase A. Its absence allows a lipid called GM2 ganglioside to build up in the brain, destroying the nerve cells. The process starts in the fetus; the disease is clinically apparent in the first few months of life. Initial symptoms vary, but usually include a general slowing of development and loss of peripheral vision. By the age of one, most children are experiencing convulsions. The damage to the nervous system progresses inexorably, bringing with it an inability to swallow, difficulty in breathing, blindness, mental retardation, and paralysis.

In late-onset Tay-Sachs, which is often misdiagnosed, the symptoms (ataxia, dysarthria, and muscle weakness) usually become apparent late in childhood or early in adulthood. About 40% of the patients display symptoms of bipolar disorder. Life expectancy does not appear to be affected.


Genetic Basis and Screening

Tay-Sachs disease occurs primarily among Jews of Eastern European descent but is also found in French Canadians whose roots are in the St. Lawrence region, certain Cajuns in Louisiana, and some Amish communities. Tay-Sachs is an autosomal recessive disorder; a person must have two defective genes (one from each parent) in order for the disease to occur. Carriers, people with only one gene for the disorder, are physically unaffected. When both parents are carriers, each child has a 25% chance of getting the disease. If only one parent is a carrier, there is no chance that the child will get the disease, but there is a 50% chance that the child will be a carrier. The gene may be carried by many generations without a manifestation. For this reason, plus the historical lack of accurate diagnosis and routinely high infant mortality of past generations, there is often no known family history of the disease.

Genetic screening for the disease has been possible since the early 1970s and is encouraged in high-risk populations. Blood tests of carriers reveal a reduced amount of the hexosaminidase A. If a couple elects to go forward with a pregnancy, fetal status (again utilizing hexosaminidase A levels) can be ascertained via chorionic villus sampling or amniocentesis. Genetic screening and counseling has greatly reduced the incidence of the disease.












tetanus

acute infectious disease of the central nervous system caused by the toxins of Clostridium tetani. The organism has a widespread distribution and is common in the soil, human and animal feces, and the digestive tracts of animals and humans; however, the toxin is destroyed by intestinal enzymes. Infection with the tetanus bacillus may follow any type of injury, whether incurred indoors or out, including nail puncture wounds, insect bites, splinter injuries, gunshot wounds, burns, lacerations, and fractures. Deep puncture wounds are most dangerous, since the bacillus thrives in an anaerobic environment.

The tetanus toxin, one of the most potent poisons known, acts on the motor nerves and causes muscle spasm at the site of infection and in other areas of the body. The most frequent symptom is stiffness of the jaw (lockjaw) and facial muscles. Difficulty in breathing and severe convulsions may ensue. The mortality rate is very high, especially in the very young and the aged; overall it is about 40%. Treatment with tetanus antitoxin should be started promptly in conjunction with human immune globulin. It is preferable, however, to prevent the disease by active immunization (including booster shots) with tetanus toxoid (see vaccination).











tetany

condition of mineral imbalance in the body that results in severe muscle spasms. Tetany occurs when the concentration of calcium ions (Ca++) in extracellular fluids such as plasma falls below normal. The nervous system becomes increasingly excitable, and nerves discharge spontaneously, sending impulses to skeletal muscles and causing spasmodic contractions. Mild tetany is characterized by tingling in the fingers, toes, and lips; acute tetany, consisting of severe muscular contractions, tremors, and cramps, can result in death. Abnormally low extracellular calcium ion concentration can result from failure of the parathyroid glands to release parathyroid hormone, the substance responsible for the regulation of calcium concentration in the body; a deficiency in vitamin D, which facilitates calcium ion absorption from the gastrointestinal tract; or alkalosis, an excessively alkaline state of body fluids resulting from persistent vomiting, rapid breathing, or excess activity of the hormone aldosterone. Most forms of tetany can be treated with calcium, vitamin D, and a controlled diet. Muscle tetany is also caused by the pathogenic bacterium Clostridium tetani in the disease tetanus.









thrombosis

obstruction of an artery or vein by a blood clot (thrombus). Arterial thrombosis is generally more serious because the supply of oxygen and nutrition to an area of the body is halted. Thrombosis of one of the arteries leading to the heart (heart attack; see infarction) or of the brain (stroke) can result in death and, in a vessel of the extremities, may be followed by gangrene. Acute arterial thrombosis often results from the deposition of atherosclerotic material in the wall of an artery, which gradually narrows the channel, precipitating clot formation (see arteriosclerosis). A thrombus that breaks off and circulates through the bloodstream is called an embolus.











thrush

in medicine, infection caused by the fungus Candida albicans, manifested by white, slightly raised patches on the mucous membrane of the tongue, mouth, and throat. The mucous membrane beneath the patches is usually raw and bleeding. The overgrowth of this fungus results when the balance in the normal oral microbe population is disturbed by antibiotic therapy or disease. It occurs most frequently in infants, in adults suffering from chronic illnesses, in the debilitated, in the immunosuppressed, and in individuals on long-term antibiotic, corticosteroid, or antineoplastic therapy. It is often an early symptom of AIDS. Treatment is with antifungal drugs, such as nystatin.

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toxemia

disease state caused by the presence in the blood of bacterial toxins or other harmful substances. The effects of the bacterial toxins known as endotoxins are relatively uniform, regardless of which bacterial species the toxin comes from, and are separate from the effects caused by the infecting bacterium itself. A small amount of endotoxin (released by dead bacteria) produces one or more fever episodes, thought to be caused by release of a fever-inducing substance from damaged white blood cells. Large quantities of endotoxin cause shock and death. Exotoxins are proteins released by bacteria that have specific effects on target tissues, e.g., botulinus toxin affects the nervous system.

The term toxemia is also used for a disorder occurring during the latter half of pregnancy characterized by high blood pressure, the appearance of protein in the urine, and edema. If not treated it can result in convulsions and coma. The cause of toxemia of pregnancy has not been established with certainty.









toxic shock syndrome

toxic shock syndrome (TSS). acute, sometimes fatal, disease characterized by high fever, nausea, diarrhea, lethargy, blotchy rash, and sudden drop in blood pressure. It is caused by Staphylococcus aureus, an exotoxin-producing bacteria. Toxic shock was initially identified among menstruating women using high-absorbency tampons that contained synthetic materials, now no longer used, that bound and removed magnesium from the surrounding bodily environment. The resulting lower magnesium levels encouraged bacterial exotoxin production. Slightly more than half of all cases now occur in menstruating women; nonmenstruating women, men, and children may also develop TSS, as a result of infection after surgery and other causes. Treatment mainly involves supportive measures, such as intravenous fluids and, if necessary, kidney dialysis, but may include antibiotics and immunoglobulin.













trachoma

infection of the mucous membrane of the eyelids caused by the bacterium Chlamydia trachomatis. Trachoma infects more than 150 million people worldwide. An estimated 6 million people have become blind because of it, making the disease the second leading cause of blindness, after cataracts. It is most common in parts of Africa, the Middle East, and Asia. In the United States it has occurred sporadically among Native Americans and in mountainous areas of the South.

Trachoma is highly contagious in its early stages and is transmitted by direct contact with infected persons or articles (e.g., towels, handkerchiefs) and possibly also by flies. It begins as congestion and swelling of the eyelids with tearing and disturbance of vision. The cornea is often involved. If left untreated, scar tissue forms, which causes deformities of the eyelids and, if there is corneal involvement, partial or total blindness. The disease has been effectively treated with tetracycline ointment and with the newer oral drug azithromycin (Zithromax). The World Health Organization began a campaign in 1998 to eradicate the disease worldwide by the year 2020. The strategy includes use of azithromycin and sanitation improvements in water supplies.












trench mouth

common term for Vincent's infection, an ulcerative membranous infection of the gums and mouth, by noncontagious infection, associated with a fusiform bacillus and a spirochete. Poor oral hygiene, nutritional deficiencies, insufficient rest, heavy smoking, and debilitating diseases are predisposing factors to the disease. Epidemics often occur in crowded unsanitary environments, and in former years among soldiers in the field, hence the name “trench mouth.” In addition to ulcerations on the gums and mouth, which are painful and bleed freely, there are usually foul breath, increased salivation, and difficulty in swallowing and talking. The acute phase of the disease yields to antibiotic treatment and oxygenating mouth rinses, but attention must also be paid to the underlying dental and medical factors.













trichinosis

parasitic disease caused by the roundworm Trichinella spiralis. It follows the eating of raw or inadequately cooked meat, especially pork. The larvae are released, reach maturity, and mate in the intestines, the females producing live larvae. The parasites are then carried from the gastrointestinal tract by the bloodstream to various muscles, where they become encysted. It is estimated that 10% to 20% of the adult population of the United States suffers from trichinosis at some time. In many people the disease exhibits no symptoms and is discovered only at autopsy. In others it causes diarrhea and other gastrointestinal symptoms as the worms multiply in the digestive tract. When the larvae circulate through the bloodstream, the patient experiences edema, irregular fever, profuse sweating, muscle soreness and pain, and prostration. There may be involvement of the central nervous system, heart, and lungs; death occurs in about 5% of clinical cases. Once the larvae have imbedded themselves in the muscle tissue, the cysts usually become calcified; however, the infestation usually causes no further symptoms except fatigue and vague muscular pains. There is no specific treatment.










tuberculosis

tuberculosis (TB), contagious, wasting disease caused by any of several mycobacteria. The most common form of the disease is tuberculosis of the lungs (pulmonary consumption, or phthisis), but the intestines, bones and joints, the skin, and the genitourinary, lymphatic, and nervous systems may also be affected.

There are three major types of tubercle bacilli that affect humans. The human type (Mycobacterium tuberculosis), first identified in 1882 by Robert Koch, is spread by people themselves. It is the most common one. The bovine type (M. bovis) is spread by infected cattle but is no longer a threat in areas where pasteurization of milk and the health of cattle are strictly supervised. The avian type (M. avis) is carried by infected birds but can occur in humans. The tubercle bacillus can live for a considerable period of time in air or dust. The most common means of acquiring the disease is by inhalation of respiratory droplets.


Course of the Disease

Tuberculosis of the lungs usually results in no or minimal symptoms in its early stages. In most persons the primary infection is contained by the body's immune system, and the lesion, called a tubercle, becomes calcified. In many the infection is permanently arrested. In others the disease may break out again and become active years later, usually when the body's immune defenses are low. Untreated, the infection can progress until large areas of the lung and other organs are destroyed. Symptoms of the disease include cough, sputum, bleeding from the lungs, fever, night sweats, loss of weight, and weakness.

Incidence

The incidence of tuberculosis of the lungs, the “white plague” that formerly affected millions of people, declined from the 1950s until 1984; sanatoriums were closed and routine screening was abandoned in the United States. Then, between 1984 and 1992, the incidence increased by 20%, chiefly because of immigration from countries where it is common and because of AIDS, which leaves people particularly vulnerable to the disease. Renewed efforts at control and advances in treatment have been rewarded with incidence declines each year, amounting to a total decline of 31% from 1992 to 1998.

Worldwide the outlook has been far less encouraging. In 1993 the World Health Organization declared TB a global health emergency. Approximately one third of the world's population is infected, and an estimated 1.6 million die each year. The vast majority of new cases occur in sub-Saharan Africa. Spread of TB is especially rapid in areas with poor public health services and crowded living conditions. In homeless shelters and prisons, crowded conditions and inadequate treatment often go together. Areas where living conditions are disrupted by wars, famine, and natural disasters also are heavily affected.

Especially alarming has been the spread of drug-resistant strains of TB. By the late 1990s scientific experts and international health officials warned that drug-resistant strains were spreading faster than had been anticipated. Bacteria can survive and become drug resistant in patients whose treatment is not properly monitored and seen to completion. Multidrug resistant TB strains are resistant to two or more of the commonly prescribed first-line drugs, while extreme drug resistant strains are also resistant to three or classes of the more toxic second-line drugs. Some believe that unless major new treatment strategies are initiated in source countries, drug-resistant TB will eventually become epidemic even in areas with good control programs, such as Europe and America.

Diagnosis and Treatment

Diagnosis is made by a tuberculin skin test. It can be confirmed by X rays of the chest and sputum examination. Ideally, treatment begins after a skin test signals exposure but before active disease has developed. The treatment of choice for prevention and for active cases is the antimicrobial drug isoniazid (INH), available since 1956. In infected individuals it is usually used in combination with other antituberculosis drugs such as rifampin, pyrazinamide, and ethambutol. Tuberculosis drugs have to be taken regularly, typically for 6 to 12 months. Many patients abandon their treatment when they feel better; similarly, preventive treatment is often abandoned because of the inconvenience. Such noncompliance is believed to be the main reason for the upsurge in drug-resistant strains of the TB bacilli, many of which are resistant to more than one drug. Drug-resistant TB is difficult to treat and has a much higher death rate; extreme drug resistant TB is especially worrisome because it can be essentially untreatable.

The combination drug rifater (rifampin, isoniazid, and pyrazinamide) has simplified drug administration. Directly observed treatment, where health-care workers watch patients take each dose of medicine, has proved effective in eliminating the problem of noncompliance in the United States, but monitoring has been less effective in many other parts of the world.

Prevention of Tuberculosis

Preventive measures include strict standards for ventilation, air filtration, and isolation methods in hospitals, medical and dental offices, nursing homes, and prisons. If someone is believed to have been in contact with another person who has TB, preventive antibiotic treatment may have to be given. Infected persons need to be identified as soon as possible so that they can be isolated from others and treated.

An antituberculosis vaccine, bacille Calmette-Guérin, or BCG vaccine, was developed in France in 1908. Although there is conflicting evidence as to its efficacy (it appears to be effective in 50% of those vaccinated), it is given to over 80% of the world's children, mostly in countries where TB is common; it is not generally given in the United States. Federal health officials in the United States have stated (1999) that a new vaccine is essential to TB prevention. It is hoped that the determination of the complete DNA (genome) sequence of Mycobacterium tuberculosis, achieved in 1998, will hasten the development of an effective vaccine.













typhus

any of a group of infectious diseases caused by microorganisms classified between bacteria and viruses, known as rickettsias. Typhus diseases are characterized by high fever and an early onset of rash and headache. They respond to antibiotic treatment with tetracycline and chloramphenicol and can be prevented by vaccination. Epidemic typhus, the most serious in the group, is caused by Rickettsia prowazeki, which is transmitted in the feces of body lice. It occurs in crowded, unsanitary conditions and has historically been a major killer in wartime. It occurs more commonly in cooler climates and seasons. Brill's disease, also called recrudescent typhus, is believed to be a milder recurrence of epidemic typhus. Endemic murine typhus is primarily a disease of rodents and is spread to humans by rat fleas. The symptoms are milder than those of epidemic typhus. Scrub typhus (Tsutsugamushi fever) is carried to humans by infected mites. It occurs primarily in East Asia and the Southeast Pacific islands.













typhoid fever

generalized infection caused by Salmonella typhi. The main sources of infection are contaminated water or milk and, especially in urban communities, food handlers who are carriers. The symptoms of typhoid appear 10 to 14 days after infection; they include high fever, rose-colored spots on the abdomen and chest, diarrhea or constipation, and enlargement of the spleen. Complications, especially in untreated patients, may be numerous, affecting practically every body system, and they account for the mortality rate of 7% to 14%. Perforation of the intestine with hemorrhage is not uncommon. Chloramphenicol is the most effective drug in combating typhoid, and in very toxic patients a cortisone derivative may be helpful. Skilled nursing care is still of the utmost importance, as is a high caloric diet to prevent wasting of the body. Vaccination against typhoid is a valuable preventive measure, especially for persons in military service and for those who travel to poorly sanitized regions.

U

ulcer

open sore or circumscribed erosion, usually slow to heal, on the skin or mucous membranes. It may develop as a result of injury; because of a circulatory disturbance, e.g., in varicose veins or after prolonged bed rest; or in association with such diseases as tuberculosis, syphilis, or leprosy. Corneal ulcers, which result from infection, allergy, or foreign objects in the eye, can cause visual impairment if not treated promptly. Some ulcers may develop into cancer. The underlying cause must be treated as well as the ulcerous lesion.

Peptic ulcer occurs in the mucous membrane of the intestinal tract. An estimated 90% of peptic ulcers are caused by infection with a bacterium, Helicobacter pylori, strains of which promote the formation of ulcers by causing an inflammtory response in the cells of the stomach wall, making it more susceptible to the hydrochloric acid secreted by the stomach. Most commonly, it occurs in the stomach (gastric ulcer) or at the beginning of the small intestine (duodenal ulcer, the most common form) and causes abdominal pain, especially between meals.

Infection with the H. pylori bacterium, which is also associated with some stomach cancer, is very common, but not all strains promote the formation of ulcers. Approximately 50% of those over 60 in developed countries are infected; in developing countries the infection rate is much higher, and infection usually occurs earlier in life. Experts are as yet uncertain how the bacterium is spread. Around 20% of those infected develop ulcers. Peptic ulcer is found more frequently in men. Heavy aspirin or ibuprofen use and smoking increase the risk of ulcer development.

The connection of H. pylori infection with peptic ulcer was made in the early 1980s by Australian scientists Barry J. Marshall and J. Robin Warren; it previously was believed that peptic ulcers were caused by emotional stress. Marshall and Warren were awarded the Nobel Prize in physiology or medicine in 2005 for their work. Treatment changed accordingly and now typically consists of antibiotics (such as clarithromycin or amoxicillin) plus metronidazole (Flagyl) and bismuth subsalicylate (e.g., Pepto-Bismol). For the relief of symptoms, drugs such as ranitidine (Zantac), famotidine (Pepcid), cimetidine (Tagamet), and omeprazole (Prilosec) may also be used. Hemorrhage or perforation of peptic ulcers requires emergency medical treatment.

The full set of genes (genome) of H. pylori was determined in 1997. This achievement will help researchers design new drugs to treat and prevent diseases caused by the bacterium.












uremia

condition resulting from advanced stages of kidney failure in which urea and other nitrogen-containing wastes are found in the blood. Uremia can be caused by NSAIDs (nonsteroid anti-inflammatory drugs), especially in older patients treated primarily with ibuprofen for arthritis. Some of the early signs of uremia are lethargy, mental depression, loss of appetite, and edema; later symptoms include diarrhea, anemia, convulsions, coma, and a gray-brown coloration. Treatment of uremia, which is directed at the underlying kidney disease, is usually with dialysis and renal transplantation. Treatments with genetically engineered erythropoietin decrease the complication of anemia.

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V

varicose vein

superficial vessel that is abnormally lengthened, twisted, or dilated, seen most often on the legs and thighs. Varicose veins develop spontaneously, and are usually attributed to a hereditary weakness of the vein; the valves in the vein that keep the blood circulating upward toward the heart are usually incompetent. Increased pressure from long standing or exertion, or internal factors such as pregnancy, or lessened support by the tissues surrounding the veins that occurs with aging and obesity causes the weakened veins to dilate. Mild varicosities often cause no discomfort. Persons with more severe cases may develop swelling of the legs, ankles, and feet, and local eczema or ulcers. Mild varicosities may be treated with rest, elevation of the legs, and the use of elastic bandages or stockings. In severe cases surgical treatment may be necessary. Traditional surgery involves tying off and removing a vein segment. Varicose veins may now also be treated without removing them through an endoscopic surgical procedure that uses the heat produced by radio waves or a laser to seal off the veins. Varicose veins that occur around the rectum are called hemorrhoids, and those that form in the scrotum are called varicoceles.











vertigo

sensations of moving in space or of objects moving about a person and the resultant difficulty in maintaining equilibrium. True vertigo, as distinguished from faintness, lightheadedness, and other forms of dizziness, occurs as a result of a disturbance of some part of the body's balancing mechanism, located in the inner ear (e.g., vestibule, semicircular canals, auditory nerves). Labyrinthitis, or infection and irritation of the middle and inner ear, is a common cause of vertigo. Elimination of infectious, toxic, or environmental factors underlying the disturbance is essential for permanent relief.










vomiting

ejection of food and other matter from the stomach through the mouth, often preceded by nausea. The process is initiated by stimulation of the vomiting center of the brain by nerve impulses from the gastrointestinal tract or other part of the body. The vomiting center then sends out nerve impulses that precipitate spasmodic muscular contractions of the stomach wall and downward spasms of the diaphragm. The pressure generated then forces up the contents of the stomach. The vomiting mechanism may be in response to local irritation (diseases or disorders of the gastrointestinal tract, overburdening of the capacity and digestive capabilities of the stomach, ingestion of harmful foods or substances) or result from a metabolic disturbance (as in pregnancy) or from disorders or stimulation of the nervous system (e.g., migraine, motion sickness, infectious disease, brain tumor or injury, disagreeable odors). Vomiting may also be a reflex action to other spasmodic conditions (whooping cough, gagging).

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W

wart

circumscribed outgrowth of the skin caused by a filterable virus that is readily transmitted. Warts may appear anywhere on the skin but are most common on the hands. Sexually transmitted diseases and human papillomavirus produce warts in the genital area; these are often precancerous growths. Some warts disappear spontaneously; others persist for many years. However, there is also a tendency to develop new lesions. Warts are treated by surgical excision (sometimes by electrocautery), bloodless removal by freezing with liquid nitrogen, or repeated applications of ointments or creams. Those on the soles of the feet (plantar warts) are the most painful and most difficult to treat, since on pressure-bearing areas they may become depressed beneath the surface of the skin.










wen

benign, slow-growing, painless cyst of the skin resulting from obstruction of the sebaceous gland ducts. It is frequently found on the scalp, ears, face, back, or scrotum. Usually no treatment is required. Large wens may be surgically removed.










West Nile virus

microorganism and the infection resulting from it, which typically produces no symptoms or a flulike condition. The virus is a flavivirus and is related to a number of viruses that cause encephalitis. It usually is transmitted through the bite of several mosquito species, and can infect humans and more than 200 animal species, including alligators, horses, and many common birds. A number of North American bird species, including the blue jay, crow, and house sparrow, act as reservoirs of the virus.

About one fifth of humans infected with the virus develop West Nile fever, which in most people is characterized by fever, headache, muscle ache, joint pain, nausea and vomiting, and in some cases rash and swollen lymph nodes (swollen glands). Less than 1% of all persons infected may develop a severe case, progressing to encephalitis or meningitis, about a week after the initial symptoms of West Nile fever appear. Loss of vision, tremors and convulsions, paralysis, coma, and, in some cases, death may result. Older persons and persons with a weakened immune system are most susceptible to severe cases of the disease, and they may suffer from longer-term effects including weakness and fatigue, headaches, memory loss and confusion, and depression. There is no treatment or vaccine for the virus except to alleviate the symptoms; controlling the mosquitoes that carry the disease is the most effective way to limit its spread.

West Nile virus was first identified in 1937 in the West Nile district of Uganda. It was subsequently found in much of the rest of Africa, the Middle East, and warmer regions of Asia and Europe. Its first recorded appearance in the United States was in Queens, N.Y., in 1999, and it since has spread to most of the United States and neighboring areas in North America.











whooping cough

whooping cough or pertussis,highly communicable infectious disease caused by the bacterium Bordetella pertussis. The early or catarrhal stage of whooping cough is manifested by the usual symptoms of an upper respiratory infection with bronchial involvement. After about two weeks the cough becomes paroxysmal; 10 to 15 coughs may follow in rapid succession before a breath is taken, which is the characteristic high-pitched crowing “whoop.” An attack of coughing is accompanied by a copious discharge of mucus and, often, vomiting. Antibiotics and hyperimmune human serum are valuable in treatment. Rest and proper nutrition (especially if there is frequent vomiting) are important.

Whooping cough is a serious disease, especially in children under four years of age, since it may give rise to such complications as pneumonia, asphyxia, convulsions, and brain damage. For these reasons, it is recommended that all infants be actively immunized at as early an age as possible (one to two months). The whole-cell pertussis vaccine available in the United States since the 1940s (see vaccination) became the subject of controversy when it was learned that a toxin contained in it could cause serious side effects and rarely death. A new, acellular vaccine, which uses only the parts of the bacterium that stimulate immunity and is less likely to cause side effects, was approved for use in 1996. It is now believed that adults whose childhood vaccinations are no longer completely effective and whose symptoms are less diagnostic may be the main carriers for the disease; booster vaccinations are recommended for 11- and 12-year-olds and adults as a means of ameliorating this situation.

Y

yaws

tropical infection of the skin caused by a spirochete (Treponema pertenue) closely related to that causing syphilis. Yaws, however, is not a sexually transmitted disease, i.e., it is not contracted by sexual contact; transmission is through ordinary contact with infected persons or their clothing and by insects. An ulcerating lesion (“mother yaw”) appears at the site of contact. The second stage of the disease begins 6 to 12 weeks later, when similar ulcerating lesions appear all over the body. If the disease is not treated, the third stage develops several years later, nodular and ulcerating lesions affecting the soles of the feet (“crab yaws”) and penetrating the bones with destructive changes. The first and second stages of yaws are easily treated with penicillin and other antibiotics. Yaws is rarely fatal; however, it can lead to chronic disfigurement and disability.










yellow fever

acute infectious disease endemic in tropical Africa and many areas of South America. Epidemics have extended into subtropical and temperate regions during warm seasons. In 1878 a severe outbreak in the Mississippi Valley killed about 20,000; the last epidemic in the United States occurred in New Orleans in 1905. Yellow fever is caused by a virus transmitted by the bite of the female Aedes aegypti mosquito, which breeds in stagnant water near human habitations. A form of the disease called sylvan yellow fever is transmitted in tropical jungles by other species of mosquitoes that live in trees.

At the end of the 19th cent., yellow fever was highly prevalent in the Caribbean, and a way of controlling it had to be found before construction of the Panama Canal could be undertaken. In 1900 an American commission headed by Walter Reed and including James Carroll, Jesse Lazear, and Aristides Agramonte gathered in the U.S. Army's Camp Columbia in Cuba. Through their experiments they proved the theory of C. J. Finlay that yellow fever was a mosquito-borne infection. Within the next few years, W. C. Gorgas, an army physician and sanitation expert, succeeded in controlling the disease in the Panama Canal Zone and other areas in that part of the world by mosquito-eradication measures. The later development of an immunizing vaccine and strict quarantine measures against ships, planes, and passengers coming from known or suspected yellow-fever areas further aided control of the disease.

Yellow fever begins suddenly after an incubation period of three to five days. In mild cases only fever and headache may be present. The severe form of the disease commences with fever, chills, bleeding into the skin, rapid heartbeat, headache, back pains, and extreme prostration. Nausea, vomiting, and constipation are common. Jaundice usually appears on the second or third day. After the third day the symptoms recede, only to return with increased severity in the final stage, during which there is a marked tendency to hemorrhage internally; the characteristic “coffee ground” vomitus contains blood. The patient then lapses into delirium and coma, often followed by death. During epidemics the fatality rate was often as high as 85%. Although the disease still occurs, it is usually confined to sporadic outbreaks.

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Newborn jaundice is not as dangerous as we thought 20 years ago. We used to start phototherapy at 12 where now we start treating it at 19 blood level of bilirubin (jaundice). It is more severe in breast fed babies and infants with uncommon blood disorders. It is helped by indirect light from a window. It is also lowered by giving one bottle of formula a day in the evenings (it will not turn them off to breast feeding.) Jaundice hits it’s peak usually around 3-4 days of age but there are exceptions. A small amount of jaundice can persist for 2 months with breast fed babies. There are rare liver disorders that can cause increased jaundice at 6-8 weeks of age. The face and chest get yellow at very low levels of jaundice. Press on the bottom of their feet and then release it. If that area of their feet that you pressed on looks yellow then call to get a blood test on the baby to see if it is real high.

Then the babies get yellow around 9-15 months old from the yellow vegetables. Their eyes are not yellow and this in not jaundice. It is Carotenemia from the carotene (Vit. A) found in squash, carrots and sweet potatoes. This is not dangerous and does not need to be treated. Older children who get hepatitis A hardly ever turn jaundiced. They have an upset stomach for a week and get over it. The main reason I diagnose it in children is so I can give a shot to the parents to prevent them from getting it. Although a mild illness in children, it is very serious in adults and 1/500 die! Like many illnesses, it is usually worse in adults. Ever seen chicken pox in a child verses an adult. Just like the Flu: 30+ children die of the flu in all of America, but 35,000 adults die of the flu every year. The press can scare you more with the children than with adults dieing. We now recommend the vaccine of Hepatitis A for those living in the counties of Texas that boarder Mexico and those children and adults going to underdeveloped countries for a while.

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