In the 1860s, it was called "neurasthenia," and considered to be a neurosis characterized by weakness and fatigue. In the 1960s it was called "Icelander's disease." Since then, physicians have blamed the symptoms variously on "iron-poor blood" (anemia), low blood sugar (hypoglycemia), allergies, or a body-wide yeast infection (CANDIDIASIS). In the mid-1980s, the disease was believed to be caused by the Epstein-Barr virus, after scientists found signs of the EBV antibodies in affected patients. Since then, scientists realized that the EBV is so common, it is actually found in the blood of many healthy Americans, while some people with no EBV antibodies have the symptoms of chronic fatigue syndrome.
The degree to which patients are disabled varies widely. Some can still function at home and work, but others become severely disabled and can't perform many of the routine activities of daily living. The total number of affected people in the United States is unknown.
In other countries, CFS is known as myalgic encephalomyelitis, post-viral fatigue syndrome, chronic fatigue and immune dysfunction syndrome.
Cause No one knows the cause of CFS, and no virus or antibody has been identified. This has made it more difficult to determine how many people actually have the illness. Based on the first three years of an ongoing surveillance study in four U.S. cities, the Centers for Disease Control estimates the minimum rate of CFS in the United States to be 4 to 10 cases per 100,000 adults.
Recent research at Johns Hopkins suggests that at least some CFS sufferers may in fact have a condition in which inadequate upper-body blood pressure causes fainting spells. For these patients, treatment with drugs and high-sodium diets to raise blood pressure resolved the CFS symptoms. In one of the most recent studies, 16 of 23 people with CFS were found to also have this low-blood-pres sure problem. After treatment with salt supplementation and drugs, nine patients were completely recovered and seven others had marked improvement in symptoms. This plus many other remedies have been tried.
Scientists have also studied a range of other possible causes, including EPSTEIN-BARR and other HERPES infections, the yeast organism CANDIDA ALBICANS, and immune system or hormone regulation problems. Many of these problems are found among CFS patients, but scientists have not yet been able to establish any of them as the source of CFS.
Symptoms To be diagnosed with chronic fatigue syndrome, a patient must have an unexplained persistent fatigue that is not caused by exertion or alleviated by rest; it must severely curtail activities. In addition, the patient must have any four of the following symptoms for at least six months that were not present before the fatigue:
• impaired memory or concentration
• tender lymph nodes in neck or under arms
• multi-joint pain
• sleep that isn't refreshing
• malaise following exercise
Many of these symptoms mimic the flu, but the flu goes away while CFS symptoms persist or recur frequently for more than six months. Many people first notice symptoms after an acute infection (cold, BRONCHITIS, HEPATITIS, MONONUCLEOSIS, or intestinal flu).
The course of the disease varies from one patient to the next. For most, the disease hits a plateau early on and ebbs and flows thereafter. Some get better, but are not completely well. Others spontaneously recover.
Treatment Although no specific treatment has been identified for CFS, there have been anecdotal reports of success with small numbers of patients using a range of treatment, including antiviral drugs, antidepressants, or drugs that boost the immune system. Many physicians prescribe tricyclic antidepressants, since these drugs help people with fibromyalgia (a disease much like CFS). Some patients improve with benzodiazepines (a class of drug used to treat anxiety and sleep problems).
Nonsteroidal antiinflammatory drugs may help ease body aches and fever; nonsedating antihistamines may help relieve allergic symptoms.
For a packet of information on chronic fatigue syndrome, contact: NIAID, Office of Communications, Building 31, Rm. 7A50, 9000 Rockville Pike, Bethesda, MD 20892.
ciguatera A common clinical syndrome caused by eating certain tropical marine reef fish (mostly barracuda, red snapper, amber-jack, surgeonfish, sea bass, and grouper). The fish are toxic at certain times of the year when they ingest a certain type of dinoflagellate called Gambierdiscus toxicus, which contains "ciguatoxin," an odorless, tasteless poison that can't be destroyed by either heating or freezing.
Ciguatera occurs most often in the Caribbean Islands, Florida and Hawaii, and the Pacific Islands. Recent reports cited 129 cases over a two-year period in Dade County, Florida, alone. It appears to be occurring more often, because we now recognize it.
Cause Ciguatera occurs after eating any of more than 300 species of fish that may contain ciguatoxin, which is found in greatest concentration in internal organs, but it can't be detected by inspection, taste, or smell. The likelihood that ciguatoxin is present is greater with larger, more predatory coral reef fish.
Symptoms Eating a fish contaminated with ciguatoxin produces both stomach and neurologic symptoms. Patients often report a curious type of sensory reversal, so that picking up a cold glass would cause a burning hot sensation. Other symptoms include a tingling sensation in the lips and mouth followed by numbness, nausea, vomiting, abdominal cramps, weakness, headache, vertigo, paralysis, convulsions, skin rash; coma and death from respiratory paralysis occur in about 12 percent of cases. Subsequent episodes of ciguatera may be more severe.
clonorchiasis A parasitic infection caused by flatworms in raw or improperly cooked or pickled freshwater fish. Saltwater fish don't carry these parasites. Clonorchiasis occurs in China, Hong Kong, Vietnam, Korea, Japan, and Taiwan. The infection is rarely fatal, and most victims recover completely.
Cause The infestation begins when the worm eggs are eliminated into water in human or animal feces and are eaten by certain snails. The eggs hatch inside the snail, where they develop into many free-swimming larval organisms that escape into the water and penetrate under the scales or in the flesh of freshwater fish. Humans become infected when they eat the fish raw or undercooked. Once inside a human host, the organism migrates to the human bile ducts, where they mature and remain for their life span, shedding eggs into the bile.
Symptoms Most people aren't infected with many parasites, and have no symptoms. If acute symptoms do occur, they include fatigue, fever, and abdominal pain. Chronic symptoms include weakness, lack of appetite, abdominal pain, diarrhea, prolonged low-grade fever, and jaundice.
Treatment Medication is available to get rid of the parasites.
Prevention Pickling, smoking, or drying fish may not destroy these infective organisms in freshwater fish. Thorough cooking is the best way to prevent the infection.
clostridial myonecrosis See GANGRENE.
Clostridium A genus of spore-producing bacteria, named for the Greek word meaning
"spindle," found in earth throughout the world. Some forms of the bacteria are found in the intestines and stools of different mammals (including humans). Others produce toxins as they multiply. These germs, which can't thrive in the presence of oxygen, can cause food poisoning and wound infection.
The genus includes the deadly CLOSTRIDIUM BOTULINUM, cause of BOTULISM. CLOSTRIDIUM PERFRINGENS is a more common and much less dangerous cause of food poisoning in the United States and is found most often in cooked beef and poultry. It is found widely in nature, and its spores can survive high cooking temperatures; if the food cools slowly, the spores germinate and the bacteria become activated. If the tainted food is served without reheating properly, live toxin-producing bacteria can be consumed, causing cramps and diarrhea in about 16 hours. Two separate outbreaks were traced to tainted corned beef served on a 1993 St. Patrick's Day.
CLOSTRIDIUM TETANI is a third deadly member of this bacterial family. The toxin produced by this bacteria causes TETANUS, not as often when eaten as when entering the body via a wound.
C. difficile is a recently identified cause of colitis linked to the administration of antibiotics. About 3 percent of healthy adults carry this bacterium in the intestines. When a patient takes antibiotics, the drugs can alter the balance of bacteria in the intestines and stomach, allowing C. difficile to reproduce to the point where its toxins cause diarrhea.
However, not all the types of bacteria in the genus are deadly. C. pasteurianum is a type of bacteria found in the soil that helps plants acquire nitrogen, a fundamental requirement in producing food. See also DIARRHEA AND INFECTIOUS DISEASE; ANTIDIARRHEAL DRUGS.
Clostridium botulinum A species of spore-producing bacteria that cause BOTULISM in humans. Botulinus food poisoning is caused by the ingestion of food containing toxins pro duced by this species. The spore's resistance to heat makes the spores an important cause of poisoning in improperly cooked or canned foods. In addition, the bacteria are commonly found in soil, where the spores can survive for years.
Clostridium difficile A species of bacteria that has emerged as an increasing threat to hospitals in Europe and North America, since it produces two toxins that lead to pseudo-membraneous colitis among those taking antibiotics aimed at another infection.
The bacteria are not easily eradicated and represent a significant challenge to hospital staff. The spores are highly resistant and can last for months on surfaces within the hospital. In one study, the most common sites of contamination were hospital floors and utensils associated with the disposal of feces, such as bedpans, steam flushers, and toilet seats.
Patients who are infected with this bacteria should stop taking antibiotics, and take either vancomycin or metronidazole instead.
Clostridium perfringens A species of anaerobic gram-positive bacteria (bacteria which grow in the absence of oxygen) capable of causing gas GANGRENE in humans, and a variety of digestive and urinary tract disease in livestock. The oval spores of this bacteria, also known as Clostridium welchii, are found mainly in soil and in human intestines.
Clostridium perfringens infection A mild food-borne illness caused by multiplying toxins produced by Clostridium perfringens type A bacteria in human and animal feces and in soil and water. These bacteria are also normally found in meat that hasn't been cooked.
This type of food poisoning is among the most common in the United States, with an estimated 10,000 cases each year, according to the U.S. Centers for Disease Control. Most cases go unreported.
Cause The toxin-producing organism is found in undercooked meat (such as rare beef; meat pies; burritos; tacos; enchiladas; reheated meats; or gravies made from beef, turkey, or chicken). The bacteria multiply quickly in reheated foods; once ingested, the bacteria produce illness in the digestive tract 8 to 24 hours later. A large amount of the bacteria must be ingested in order to cause illness. Outbreaks have often been traced to restaurants, caterers, and cafeterias.
The bacteria have a spore form, a dormant state that is not killed by cooking; the spores can't reproduce into bacteria at temperatures below 40 degrees F or above 140 degrees F.
Symptoms The illness appears suddenly (within 8 to 24 hours after eating), causing severe colic or cramps and abdominal gas pains followed by a 24-hour bout of watery diarrhea. There may be nausea but usually not vomiting or fever. While usually a mild illness, it can be dangerous to infants and the elderly, who may become dehydrated. Having the disease does not confer immunity, but patients are not infectious.
In injuries, this type of bacteria causes the potentially fatal gas gangrene by proliferating in the injured tissues.
Diagnosis Recently, scientists at the University of Illinois at Urbana-Champaign produced a test that can detect the presence of the bacterium. The bacteria will also grow on a culture plate in a lab from either a food or a stool sample.
Treatment Because this is technically not an infection but an intoxication, no antibiotic will cure it. Patients should try to replace fluid losses by drinking clear liquids. If dehydration is suspected, seek medical help. If food poisoning is suspected, local health departments should be notified.
Clostridium tetani One bacterial member of the genus CLOSTRIDIUM that cause tetanus, dangerous not in itself but because of the toxin it releases. Spores of this bacteria are found in soil that can enter the body via any type of wounds, from the classic deep puncture cuts to injuries as innocuous as a splinter injury.
As the bacteria are activated by decomposing tissue, the toxin travels though the nervous system into the spinal cord, triggering spasms, giving rise to the common name for this syndrome, "lockjaw." A terrible grin, called RISUS SARDONICUS, can transform the face of any untreated victim.
CMV See cytomegalovirus.
Coccidioides immitis The infectious fungal spores that cause the acute or chronic illness coccidioidomycosis.
coccidioidomycosis The medical name for valley fever, an infectious fungal disease caused by inhaling bacterial spores, which may be either acute or chronic. It is endemic in hot, dry areas of the U.S. Southwest—Central and San Joaquin valleys and desert areas of California, as well as the arid areas of Nevada, Utah, Arizona, West Texas, and New Mexico. A person who lives in one of these areas is quite likely to be affected by valley fever. For example, almost 60 percent of the residents of Bakersfield, Kern County, California, have positive skin tests for valley fever. (A positive skin test means the person has had an infection and has developed immunity to the fungus, and will never contract valley fever again.) The disease is also found in Mexico, Central America, and South America. It is a disease associated with aids.
Animals can develop the disease—especially horses, cattle, dogs, and llamas. Cats are not usually affected. Coccidioidomycosis is also known as desert fever, desert rheumatism, or San Joaquin fever.
Cause The bacterial spore Coccidioides immitis, which is carried on windborne dust particles, is the cause of the disease. The cocci fungus lives in a sort of hibernation in alkaline soil, blooming when weather conditions are good. When it blooms, the tiny spores are stirred by wind or other movement and become airborne, floating in the air for many miles. When a person or animal who is not immune breathes them in, the spores enter the lungs and cause an infection. In general, the more spores inhaled, the more serious the infection.
Symptoms About two weeks after inhaling the spores, the lungs become infected. At first, the disease resembles a flulike illness that primarily involves the lungs, with fatigue, aching, chills, sweats, fever, headache, and cough. Symptoms can be mild, never amounting to more than a slight cold (about 60 percent of cases are the mild variety). The remaining 40 percent have more severe symptoms, eventually spreading throughout the body. Along with the flulike symptoms, these patients experience skin rash and joint aches (especially the knees). Dark-skinned patients appear to have more severe symptoms and to have the disease spread to other parts of the body. However, the most serious form that valley fever takes— when it infects the lining of the brain, called cocci meningitis—is most likely to occur in Caucasian males. Cocci meningitis is the form most likely to end in death.
Diagnosis The diagnosis can be confirmed if the patient has recently visited an endemic area, and if the fungus has been identified in sputum, body fluid, or tissue.
Treatment Most patients with valley fever don't need to be treated. However, those whose disease has spread to other parts of the body need medication. Ketoconazole, fluconazole, and itraconazole are all antifungal agents approved for the treatment of valley fever. The most effective medication for treating valley fever infections is amphotericin B.
Abscesses in soft tissue, bone, and joints may need to be drained, and bone infections may need to be removed.
cold, common An upper respiratory infection caused by one of at least 200 different types of viruses. Colds are most likely to occur during "cold season," which begins in the fall and continues throughout the spring; tropical areas tend to encourage cold viruses during the rainy months. While cold viruses are found throughout the world, they infect only humans with what are considered to be upper respiratory infections, which means they are limited to the nose and throat. After one bout with a particular virus, the victim will develop an immunity to that precise virus. This is why adults have fewer colds than young children, and why the oldest Americans have the fewest colds of all.
A person who smokes or lives in a polluted atmosphere has a higher chance of coming down with a cold. This is because air pollution and the nicotine and tars in tobacco smoke can irritate the lining of the nose and throat, making it easier for a cold virus to enter the cells and cause an infection. This irritation can also prolong the length of the infection. This is why people who live in heavily polluted areas or who smoke (or live with smokers) have more colds and have them longer than those who don't.
The common cold costs Americans millions of days of missed work and school every year and more than $2 billion for over-the-counter and prescription remedies, none of which will cure the infection.
Cause Different types of viruses proliferate at different times; in the fall and late spring, a cold may be caused by one of the more than 100 types of rhinovirus. These are the most common villains, and appear to be related to crowding indoors, school openings, and seasonal variations. Between December and May, several types of coronaviruses are responsible for most cases. Besides these two types of viruses, colds may also be caused by parainfluenza, RSV, adenovirus, enterovirus, and influenza. All of these viruses seem to be able to change their characteristics from one season to the next.
A cold is NOT transmitted by sitting in a draft, getting wet feet, or going outside without a jacket. Because the cold viruses are so specific, a person can only get a cold if the virus travels high up inside the nose, into the nasopharynx. A cold virus can only reach this area by touch, or (less often) through the air. One study found that while saliva didn't pass on germs, even a very brief contact with a nasal mucous-contaminated hand (as quick as a 10-second touch) led to transmission of virus in 20 of 28 cases.
While cooling the body doesn't seem to bring on a cold, fatigue, stress, and anything else that weakens the body's immune system can influence susceptibility. It's possible to catch a cold from other people who have colds or from the things they use or touch: faucets, phones, doorknobs, light switches, straps on buses or subways, office equipment. A virus can survive for many hours on these objects, unless someone washes it off with alcohol, a household disinfectant, or hot, sudsy water. Everyone who touches one of these contaminated objects and then touches their nose, eyes, or mouth can get the virus. Once the virus is on the hands, others can be exposed by shaking hands or by touching other things that they touch.
Cold viruses are NOT carried very far through the air, however. If someone with a cold sneezes across the room, neighbors won't come down with the cold, too—but if someone should cough or sneeze right into a person's face, the person could get sick.
Healthy people have a film of mucus lining the nose and throat; tiny hairs called cilia move this mucus from sinuses and throat to the stomach. As the mucus is moved along, it traps harmful bacteria and viruses and carries them along to the stomach, where they are broken down by acids. A healthy mucous membrane can snag germs trapped in the nose and throat, then breathe, cough, or sneeze them back out. The mucus around the tonsils and adenoids can trap these germs, where they can be destroyed by the immune system.
If a person is not so healthy, the mucous membranes in the nose will be either too thick (causing a stuffy nose and congested throat) or too thin (runny nose). The germs won't be cleared away. Once the viruses enter the nose, they set up housekeeping in the mucous layer of the nose and throat, attaching themselves to cells found there. The viruses drill holes in the cell membranes, inserting their own genetic material to enter the cells. Soon, the virus takes over and forces the cells to pump out thousands of new little virus particles.
In response to this invasion, the body's immune system swings into action. Injured cells in the nose and throat release chemicals called prostaglandins, which trigger inflammation and attract infection-fighting white blood cells. (The throat will begin to feel scratchy and swollen.) Tiny blood vessels stretch, which allows spaces to open up and specialized white cells to enter. Body temperature rises and histamine is released (causing a fever), which steps up the production of mucus in the nose, trapping and removing viral particles. The nose starts to run. As the nose and throat stimulate the extra mucus production, it irritates the throat and triggers a cough. Cold viruses are also responsible for congestion in the sinuses.
All of this activity comes at a price, of course—the unpleasant symptoms experienced as "a cold." Actually, by the time a person starts feeling sick, the body has already been fighting the invader for a day or two. When people are in the process of catching a cold, they probably feel fine. It's not until they're actually getting better that they feel ill.
In order to break through the body's defenses (hair, mucus, and other barriers in the human nose) viruses must attack in huge numbers in order to successfully cause a cold.
Most of the time, a brief encounter with a sick stranger won't cause disease, even if a person sits in a doctor's office filled with sick patients for 10 or 20 minutes.
On the other hand, working all day in an office building filled with people who have colds could be a risk. Traveling on a plane carrying sick passengers is an even bigger risk for catching a cold, since the recirculated air in a pressurized cabin evenly distributes viruses to everybody, while drying out mucous membranes that would normally trap viruses and get rid of them.
Symptoms A stuffy congested nose, sneezing, sore scratchy throat, cough, headache, runny eyes, and (possibly) a low fever. Viruses that attack the lower respiratory tract—the windpipe, bronchial tubes, and lungs—are more serious but less common and are responsible for pneumonia and bronchitis, among others.
The symptoms of a cold (scratchy throat, runny nose, and congestion) aren't caused by the virus itself but are the result of the immune system's fight to get rid of the invader.
Because the symptoms of a cold are actually caused by the body's attempt at healing itself, there are times when the patient should not interfere. It's best to let a fever below 103.5 degrees burn itself out, for example, since this type of fever will also help the body burn up viruses and toxins. And mucus from a runny nose is a good way of getting rid of germs (and spreading the disease).
Treatment There is no treatment that will cure a cold, which is caused by a virus. Symptoms may be treated by a wide variety of over-the-counter medications and many different home remedies. While the use of vitamin C to treat colds is still controversial, several well-controlled studies demonstrate that it can lessen a cold's symptoms and duration. Other studies have shown that zinc lozenges can shorten the duration of symptoms.
Complications A cold usually lasts for about 10 days, although it can range from three days to several weeks. A doctor should be consulted if the patient still feels sick after 10 days. A person should call even sooner if the face starts to swell or teeth become extremely sensitive, because these symptoms can signal a bacterial infection in the sinuses or middle ear.
When the sinuses become clogged with nasal secretions, they may become infected with bacteria. While antibiotics won't touch a cold, they will be effective in treating this secondary bacterial infection.
PNEUMONIA may also set in at the end of a cold; if you suddenly develop a fever after the symptoms seem to be going away, see a doctor.
Prevention A person remains infectious from 24 hours before symptoms appear until five days after the cold starts. A person is most infectious for the first three days, from the time when the first symptoms show up. Young children are infectious for a longer period of time (up to three weeks), since it takes their immune systems longer to fight off the virus.
It may not seem practical, but a person with a cold should stay home. While most adults feel that they should force themselves to go to work if they have a cold, in fact it would be much better for everyone if they would isolate themselves to decrease the spread of the virus.
The most important factor in reducing the transmission of colds is to keep hands away from nose and eyes. By scratching the nose or rubbing the eyes with a contaminated hand, the virus can easily be inhaled higher up in the nose or enter the nasopharynx through the tear ducts of the eye. According to research, most people touch their nose or eyes about once every three hours.
Since most people find it difficult not to touch their face occasionally, washing hands often may help prevent colds. It's especially important for people who already have colds to wash their hands, since they are even more likely to be wiping, blowing, scratching, or touching the nose area. Washing the hands vigorously with soap and water for 20 seconds will remove the virus. Disposable tow-elettes are a good alternative.
Hands should be washed:
• after sneezing or coughing
• before eating
• after wiping, blowing, or touching your nose
• after using the toilet
• before touching another person
Disposable tissues should be used instead of cloth handkerchiefs when coughing, sneezing, or blowing the nose and thrown away immediately afterward. A used tissue is filled with virus just waiting to be passed on to someone else.
In addition to not touching the face and washing the hands, it's also a good idea to disinfect areas likely to be contaminated with germs, such as door handles, telephones, light switches, etc.
By being careful, it is really possible to stop the spread of colds, even if you're living in a household where others are sick.
Since plane travel brings a higher risk of catching someone else's cold, it's a good idea to drink at least 8 ounces of water for each hour spent on a plane to rehydrate the nose.
Diet There is some evidence that certain strains of rhinoviruses can be destroyed by high levels of vitamin C. Several German studies have suggested that the herb echinacea (E. purpurea, E. angustifolia, or E. pallida) appears to be mild stimulant of the immune system that may help fend off colds. Because its effect appears to fade when used on a daily basis for longer than eight weeks, it's best to use it intermittently.
Stress There is a definite link between emotions and infections, according to studies reported in the New England Journal of Medicine. In one study by Sheldon Cohen, Ph.D., professor of psychology at Carnegie-Mellon University in Pittsburgh, it is reported that a high level of psychological stress lowers resistance to viral infections and nearly doubles the chance of getting a cold. Other studies have found that mental and emotional stress impairs the ability to fight off viruses and doubles the risk of catching a cold.
Studies found that about 25 percent of those who were infected with the rhinovirus didn't develop cold symptoms; the reason, studies suggest, may be that some people have healthier immune systems than others.
Humor may also help. Levels of protective chemicals (such as IgA) jumped significantly when volunteers watched comics, according to a study by psychologist Kathleen Dillon, Ph.D., at Western New England College in Springfield, Massachusetts. Those who watched a documentary had no rise in IgA levels.
Humidity Studies suggest that the relative humidity of the air may affect the risk of colds. During the winter and the start of winter heating (with its lowered humidity), there is a sharp increase in the number of colds. This low humidity causes dry throats and nose, which increases the chance of infection.
The nose, throat, and lungs work best when the air has a relative humidity of about 45 percent. If the air during the winter falls below that level, moisture will be absorbed into the heated air from the mucous membranes. Since dried mucous membranes can't clean themselves they become more vulnerable to invasion from cold viruses.
Air circulation Good ventilation can also help disperse germs and hinder the spread of colds.
The closed circulation systems of airplanes are another potential danger for the transmis-
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