associated in particular with eating mussels, oysters, and scallops.
Symptoms Symptoms appear between a few minutes to three hours after ingestion, and include gastrointestinal problems accompanied by muscular weakness, chills, headache, and fever. Recovery is rapid and death is rare.
Diagnosis Diagnosis is based on observing symptoms and recent dietary history.
Treatment There is no antidote for this type of shellfish poison, but most people recover on their own.
shellfish poisoning, neurotoxic A type of shellfish poison that occurs when humans eat shellfish that have ingested toxin-producing plankton.
While all shellfish are potentially toxic, NSP is generally associated with shellfish harvested along the Florida coast and the Gulf of Mexico. Outbreaks are sporadic and continuous and have been reported along the Gulf coast of Florida and more recently in North Carolina and Texas.
Cause NSP is the result of exposure to a group of toxins called brevetoxins.
Symptoms Both gastrointestinal and neurological symptoms appear in this type of shellfish poisoning within a few minutes to a few hours after eating the shellfish. Symptoms include tingling and numbness of lips, tongue, and throat; muscular aches; dizziness; reversal of the sensation of hot and cold; diarrhea; and vomiting.
Recovery is complete with few aftereffects; no fatalities have been reported.
Diagnosis Diagnosis is based on observing symptoms and recent dietary history.
Treatment There is no treatment other than easing symptoms.
shellfish poisoning, paralytic (PSP) The most serious type of shellfish poisoning, PSP is a toxic neurologic condition caused by eating clams, oysters, or mussels that have ingested toxin-producing plankton. The type of toxin is called saxitoxin, among the most potent toxins known and one that is not destroyed by cooking. The saxitoxin comes from algae eaten by filter-feeding shellfish such as clams and mussels; this toxin can be present even when there is no visible discoloration (or red tide) in the ocean water. The shellfish store the toxin from the algae in their tissues and pass the toxin on to anyone who eats them. In recent years, the toxin has been found in snails and in crab viscera as well.
Most victims of this type of poisoning in the United States are individuals who have gathered shellfish for their own use. PSP has generally been considered to be dangerous only in shellfish harvested from cold water, but the incidence of red tides in warmer waters may be increasing. Outbreaks have recently been reported from Central and South America, Asia, and the Pacific.
Cause The 20 toxins responsible for paralytic shellfish poisonings are all derivatives of saxitoxin.
Symptoms Saxitoxin interferes with functions involving the brain, movement, and senses. Soon after eating (sometimes in less than an hour), symptoms appear. At first, there is a tingling or numbness in lips and tongue, often followed by tingling and numbness in the fingertips and toes, nausea, lightheadedness, followed by vomiting and diarrhea. This may progress to loss of muscle coordination. This is followed by a gradual paralysis, trembling, headache, and weakness. Death as a result of respiratory paralysis can occur within 12 hours of eating PSP-con-taining shellfish. Eating as little as 0.5 to 1.0 mg. of contaminated shellfish can be fatal, and a person's survival depends on how much has been consumed. If a person survives the first 12 hours, chances of survival are good. However, between 8 and 23 percent of PSP poisonings are fatal. The severity of the illness is less if the water used in cooking is not consumed.
Diagnosis There is no lab test that can determine the presence of PSP in an individual. Diagnosis is made on the basis of recent food consumption, symptoms, and detection of toxin in uneaten shellfish.
Treatment There is no known antidote for shellfish poisoning caused by saxitoxin-pro-ducing plankton. Administration of prostig-mine may be effective, together with artificial respiration and oxygen as needed. It is important that vomiting be induced at the onset of symptoms to help remove remaining toxin-containing shellfish and that medical attention be obtained. Drinking alcohol increases absorption of the toxin.
Prevention To prevent outbreaks of PSP, samples of susceptible mollusks are tested for toxin by state health departments during certain times of the year. Affected growing areas are quarantined, and sale of shellfish is stopped. Warning signs posted in shellfish-growing areas, on beaches, and in the news warn the public of the danger.
Because of this constant monitoring, shellfish poisoning in the United States is rare; from 1973 to 1987 only 19 outbreaks were reported, with an average of eight cases per outbreak.
Shigella group A group of four different species of bacteria that lead to the diarrheal disease known as shigellosis.
shigellosis A bacterial diarrheal disease caused by the bacterium Shigella, which includes four different species. The disease is common among the developing countries, where lack of sewage treatment leads to contaminated food and water.
Two thirds of cases are found in children between 6 months and 10 years of age, although it is rare in infants under age 6 months. The highest rates of infection occur in child care centers, large camps, and institutions.
A person is infectious from the time the diarrhea appears until the bacteria are no longer in the stool, which could take a month. Antibiotics shorten the infectious period to a week.
Cause Shiga toxin is named after Kiyoshi Shiga, who in 1898 first described the bacterial origin of dysentery caused by Shigella dysen-teriae.
The Shigella bacteria are found in milk and dairy products, poultry, and mixed salads, but they can develop in any moist food that is not thoroughly cooked. The bacteria multiply rapidly at or above room temperature. S. son-nei is the mildest of the four, and is responsible for most cases around the world. S. dysenteriae (also known as bacillary dysentery) is fairly common in rural Africa and India, where it causes illness and many deaths.
A person gets sick after ingesting bacteria; it only takes a few organisms to cause illness. The bacteria may be found in contaminated bodies of water or in food that is left out in the open where flies can contaminate it. Dogs who eat infected human feces can spread the infection to humans (especially children), and the disease can also be spread sexually with anal-oral contact.
Symptoms Symptoms, which usually appear eight hours to eight days after ingestion, begin with nausea and vomiting, watery or bloody explosive diarrhea and stomach cramps, weakness, vision problems, headache, and difficulty swallowing. Those with weakened immune systems may have more serious diarrhea and may take longer to recover. Young children have more serious symptoms, and those children already malnourished or weak will be much sicker.
Diagnosis Culture of the stool will reveal Shigella.
Treatment Most people with shigellosis recover on their own. Some may require fluids to prevent dehydration. To shorten severe cases, antibiotics will help stop the diarrhea, although Shigella has become resistant to some drugs. Trimethoprim-sulfamethoxazole, ciprofloxacin, or orofloxacin are usually effec tive; some strains are susceptible to tetracycline. Those who are infected in a developing country may respond better to nalidixic acid, since the bacteria in those locations are widely resistant.
Antidiarrheal medications should not be taken. Dilute drinks high in sugar and bland foods high in carbohydrates are tolerated best by the patient.
Prevention Confirmed Shigella cases must be reported to the health department, which will begin an investigation and control measures in order to prevent large-scale outbreaks. Although several vaccines have been tested, none have yet been licensed for use in preventing the disease. The single most important way to prevent the spread of disease is to carefully wash hands after using the toilet, since Shigella is passed in feces.
shingles A painful, red blistering viral infection of the nerves that supply certain areas of the skin, caused by reactivation of the varicella-zoster virus (VZV), the same culprit that causes childhood chickenpox.
Shingles is a common illness that strikes one in five Americans. The name comes from the Latin word cingulum, meaning "belt" or "girdle." By age 85, people have a 50-50 chance of developing shingles if they haven't already had them.
Cause After an episode of chickenpox, the virus lie dormant in sensory nerves along the spine for many years. When the immune system efficiency is weakened, the virus reemerges and migrates along the sensory nerve, breaking out at its receptor ends in the skin. Each year, shingles affects several hundred patients per 100,000 in the United States, usually over age 50.
Scientists suspect that a decline in the activity of white blood cells may allow the virus to reemerge. This idea is bolstered by the fact that shingles also appears in children with leukemia, cancer patients undergoing chemotherapy, and organ transplant patients. The virus often affects a nerve that has had previous trauma.
Symptoms The first sign is excessive sensitivity in an area of skin, followed by pain; after about five days the rash appears, turning into tense blisters that turn yellow within three more days. The blisters then dry out and crust over, gradually dropping off (leaving small pitted scars behind). Because the nerves have been damaged after the virus attack, after the blisters heal the nerves constantly produce strong pain impulses that may last for months or years.
The older the patient and more severe the rash, the more likely the pain will persist. Shingles often affects a strip of skin over the ribs on one side; sometimes it affects the lower part of the body or the upper half of the face on one side. It can occur in any area of the body.
Treatment There is little that can be done either for the rash or the pain afterward, but prompt use of antiviral drugs such as acyclovir, famcyclovir, or valacyclovir can shorten the rash stage and lessen the chance of pain later. Therefore, patients should seek medical help at the first signs of shingles. Acyclovir slows reproduction of the virus and shortens the course of the infection, although it doesn't prevent the nerve pain following a shingles attack. Some experts maintain that steroid drugs such as prednisone can prevent this pain. Valacyclovir is a chemical cousin of the widely used acyclovir; it received FDA approval in June 1995.
For severe pain from shingles, experts occasionally recommend injecting a nerve block in the appropriate place to block the sympathetic nerves supplying the area of pain. This block typically relieves pain for hours in up to 80 percent of patients.
An over-the-counter product called Zostrix or Valtrex (active ingredient: capsaicin, a red pepper derivative used to make chili powder) may help relieve the post-herpetic shingles pain, once all the blisters have disappeared.
Experts believe that capsaicin blocks the production of a chemical necessary for pain impulse transmission between nerve cells. Do not apply Zostrix to active shingles blisters. As a counterirritant, Zostrix is designed to be used on unbroken, healed skin with a pain sensation, not for open oozing infections.
Adenosine monophosphate is the newest potential treatment now being studied by researchers.
Complications Almost half of the 600,000 patients who get shingles each year suffer from agonizing pain that may last from days to years. If the pain lasts long after the rash, it is known as postherpetic neuralgia. It can also lead to bizarre sensations that can linger for years, including phantom feelings.
Sufferers complain that a light touch can feel like torture and a drop of water feels like a third-degree burn. Even the softest clothing can be unbearable to these patients.
Postherpetic neuralgia is treated with a variety of medications from amitriptyline to opioids.
Sin Nombre virus The newest strain of hantavirus (virus carried by rodents) that caused an outbreak of hantavirus pulmonary syndrome in the Four Corners area of the United States. The virus, originally named after the Muerta Canyon on the Navajo Reservation of New Mexico, has killed more than 100 patients across the United States (mostly in Arizona, New Mexico, and Colorado). Hantavirus is the third most deadly virus ever found in the United States, after hiv and rabies.
This American variety appears to be 10 times more deadly than a related hantavirus from Asia, called the Hantaan virus. Scientists suspect the Sin Nombre virus is not at all a new organism but rather one that has been living for eons in deer mice of the southwest, emerging occasionally to infect humans. Navajo legends appear to have mentioned this disease.
Because the virus has been identified as a cause of disease in patients in New York and Virginia, scientists believe that eventually the organism will be found throughout the United States.
sinusitis An inflammation of one or more of the sinuses, often as a complication of an upper respiratory infection or dental infection. (It may also be caused by allergies, air travel, or underwater swimming.) Sinusitis is extremely common and afflicts some people with every bout of the common cold. In many people, once a tendency toward sinusitis develops, the condition recurs with each viral infection.
Cause Sinusitis is often caused by infection spreading from the nose along the narrow passages that drain mucus from the sinuses into the nose. As the nasal mucous membranes swell, the openings from the sinuses to the nose may be blocked. This leads to a buildup of sinus secretions, often teeming with bacteria. The disorder is usually caused by a bacterial infection that develops as a complication of a viral infection (such as the common cold). (See cold, common.) It is also possible that an infection may occur from an abscess in an upper tooth or from infected water forced into the sinuses while swimming.
Symptoms Pressure, throbbing headache, fever, and local tenderness, together with a feeling of fullness or tension. It may also cause a stuffy nose and loss of the ability to smell.
Complication Often, sinusitis leads to the formation of pus in the affected sinuses, causing pain and a nasal discharge. Other more rare complications include orbital cellulitis, osteomyelitis, and meningitis.
Diagnosis X rays may be taken to determine the location and extent of the disorder, and a culture may be grown from a swab of the sinus to identify the bacteria.
Treatment Steam inhalations, nasal decongestants, painkillers, and antibiotics.
Surgery to improve drainage may be performed for chronic problems.
sixth disease See roseola.
skin infections Because the skin represents the outer barrier to the world, it is responsible for defending the interior of the body against a wide range of attackers, including bacteria, viruses, insect venom, and fungi. Skin infections can range from a local superficial problem (such as impetigo) to a widespread and possibly fatal infection.
Examples of bacterial skin infections include impetigo, ecthyma, folliculitis, boils, carbuncles, erysipelas, scarlet fever, cellulitis, etc. Viral infections with skin symptoms include herpes simplex, chicken-pox, and shingles, warts, measles, german measles, fifth disease, aids, etc.
sleeping sickness The common name for African trypanosomiasis, a serious infectious disease of tropical Africa caused by parasites transmitted by the bite of infected tsetse flies. About 20,000 cases are reported worldwide each year.
Cause East Africa's version of sleeping sickness is caused by the parasite Trypanosoma brucei rhodesiense and is spread mainly to wild animals, only rarely affecting humans. West Africa's chronic gambiense variety (caused by the T. brucei gambiense) may not cause the "sleeping" part of the illness until years after exposure. This variety is spread primarily from person to person. Within humans, the parasites multiply and spread to the bloodstream, lymph nodes, heart, and brain.
Symptoms With both versions of sleeping sickness, a painful nodule develops at the site of the fly bite. In the West African version, the disease progresses slowly with bouts of fever and lymph gland enlargement. After a period of months or years, the parasites invade the tiny blood vessels supplying the central nervous system. This causes the legendary drowsiness, lethargy, and sleepiness. The patient may become completely inactive, with drooping eyelids and a vacant expression (hence, the term sleeping sickness). If untreated at this point, the patient may die. The East African form is more virulent; a severe fever develops within a few weeks of infection and effects on the heart may be fatal before the disease gets to the brain.
Diagnosis Microscopic examination of the blood, lymph fluid, or cerebrospinal fluid reveals the presence of the parasites.
Treatment The drug Suramin (available from the Centers for Disease Control) can treat both versions of African sleeping sickness. Melarsoprol (a derivative of arsenic) is available from the CDC to treat final stages of both versions. If the patient is known to have the gambiense variety, the drug eflornithine (approved by the FDA) is more effective and safer.
Melarsoprol can cause serious or fatal nervous system problems in some patients, according to the FDA. Eflornithine is useful for both early and late stages of gambiense sleeping sickness; it is not effective for the rhodesiense variety. It works by interfering with the parasite's growth. In most cases, a complete cure is possible, although there may be brain damage if the infection has already spread to the brain.
Prevention Eradication of tsetse flies can help prevent spread of this disease. Visitors to rural parts of Africa should take measures to protect against tsetse fly bites.
smallpox A highly infectious serious viral disease (causing skin rash and flulike symptoms) that has been totally eradicated since 1980. A common scourge of the 19th century, smallpox was characterized by a rash that spread over the body, turning into pus-filled blisters that crusted and sometimes left deeply pitted scars. Complications included blindness, pneumonia, and kidney damage. There is no effective treatment for the disease, which kills up to 40 percent of patients.
Smallpox was eradicated through a cooperative international vaccination program. The disease affects only humans, and its victims are easily recognized and only infectious for a short time. As a result of the successful eradication program, smallpox vaccination certificates are no longer required for international travel. Most countries have stopped vaccination because the vaccine itself is now more dangerous than the disease, since the vaccine can cause encephalitis and there is now no chance of contracting smallpox.
The virus responsible for smallpox is still maintained at laboratories in Moscow and at the Centers for Disease Control in Atlanta. Some experts suggested that the virus be destroyed, but that idea was met by such criticism among the scientific community that any decision to do so has been postponed.
snail fever See schistosomiasis.
sore throat A scratchy, painful throat often accompanying a cold or other infection and caused by a variety of organisms.
Complications Although a sore throat in itself is not serious, it may indicate a bacterial infection, such as a strep throat: swollen/tender lymph nodes in the neck, fever for more than two days, and pain with swallowing.
Spanish flu See influenza.
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