Cholera is an acute infectious disease caused by the bacterium vibrio cholerae, which lives and multiples (colonizes) in the small intestine but does not destroy or invade the intestinal tissue (noninvasive). The major symptom of cholera is massive watery diarrhea that occurs because of a toxin secreted by the bacteria that stimulates the cells of the small intestine to secrete fluid. There are several strains of V. cholerae and the severity of the disease is based on the particular infectious strain.
Cholera is not a difficult disease to treat and most people recover well with appropriate oral fluid replacement (hydration). However, if the disease goes untreated, it can rapidly lead to shock, as a result of fluid and electrolyte loss, and to life-threatening complications.
The symptoms of cholera vary according to the severity of the disease. Some infected individuals may only experience a few days of mild diarrhea. Others may have more serious symptoms and prolonged diarrhea may be so severe that there is excessive fluid loss leading to shock. Rapid onset of life- threatening complications may occur in very severe cases.
The initial symptoms of cholera may include sudden painless diarrhea and vomiting. Diarrhea becomes progressively more watery and large volumes of fluid, sodium, chloride, potassium, and bicarbonate (electrolytes) are lost. Subsequent symptoms are the direct result of the fluid loss (dehydration) and electrolyte imbalance. These may include intense thirst, decreased urine output, muscle cramps, and/or general weakness. Abnormally low blood pressure (hypotension) and potassium (hypokalemia) are common. Excessive amounts of acid may accumulate in the blood and body tissues (acidosis) and shock may develop if treatment is not administered. Kidney failure may occur, but generally responds to fluid replacement.
Cholera is caused by the bacterium vibrio cholerae which is a rod-shaped gram negative organism. There are several different types of this bacteria which can produce mild or more severe forms of the disease. The symptoms of cholera develop due to the release of a toxin (Vibrio c. 01) by the bacteria.
Outbreaks of cholera are typically limited to specific geographic areas (endemic) in India and parts of the Middle East, Asia, South America, and Africa. The disease affects males and females in equal numbers. Children are more susceptible to cholera than adults, especially those children under the age of five years. Major outbreaks of cholera usually occur during the warmest part of the year. Cholera occasionally spreads to Europe, Japan, Australia, and South America where epidemics can occur any time of the year and affect persons of all ages equally.
Cholera is primarily a waterborne disease. During epidemics, cholera may spread rapidly as increasing numbers of affected individuals excrete large volumes of infected stool. Drinking, washing, and cooking water become rapidly contaminated with Vibrio cholerae bacteria, especially when sanitation conditions are substandard. During the 1990s cholera became endemic in South America and some cases were reported in the United States.
The symptoms of cholera tend to be more severe in those people with Type O blood; those with Type AB blood tend to get a less severe form of the disease. The exact reason for this difference is not fully understood.
The diagnosis of cholera is confirmed by clinical evaluation and the isolation of the V. cholerae from cultures grown with samples of fresh stool from an infected individual.
The symptoms of mild or uncomplicated cases of cholera resolve on their own (spontaneously) within 3 to 6 days of onset. The bacteria usually disappear from the gastrointestinal system within 2 weeks.
Most people with cholera require the replacement of fluids that are lost due to prolonged diarrhea. If fluids are started early, most affected individuals can replace fluids orally. The administration of intravenous fluids is necessary in very severe cases of cholera and in people who produce more than seven liters of stool volume a day. If shock occurs or if oral fluid intake is not possible (i.e., excessive vomiting), intravenous fluid replacement is essential. A variety of fluid replacements that contain salts, glucose, electrolytes, and/or bicarbonate are available, some in packet form (i.e., Pedialyte, Rice solution, Ricelyte, and WHO/UNICEF solution). These can be administered easily even without medical personnel.
The aim of fluid replacement is to restore electrolyte balance, reverse dehydration, and to restore normal blood pressure. Plasma and related products, and drugs that raise blood pressure are useless in the treatment of cholera. After the initial crisis is over, patients may continue intravenous fluid and salt replacement, or these fluids may be given by mouth.
Antibiotics will shorten the course of cholera and usually prevent severe illness if administered early. Tetracycline is the drug of choice and ampicillin is an acceptable substitute for pregnant women and children. The drug Furazolidone is usually effective against resistant strains of the bacteria.
The most important methods of prevention and control of cholera are clean water supplies and adequate sewage disposal. Water supplies must be purified and human waste must be disposed of properly. Individuals in areas where cholera is endemic should boil all water and avoid eating uncooked vegetables and ice.
People living in endemic areas usually develop an immunity to the cholera bacterium. Travelers to these areas should be vaccinated against the disease. Vaccines against cholera are available but are not 100 percent effective; booster injections are required every 6 months. Tetracycline may be administered to prevent the disease (prophylaxis) if a person is exposed to contaminated food or water. Travelers to South America, Middle East, Asia, and Africa should check with the Centers for Disease Control (CDC) to determine areas of endemic cholera and availability of the cholera vaccine.
Research on the prevention, control, and treatment of tropical diseases such as cholera is ongoing. For more information about these disorders contact the World Health Organization (WHO) listed in the Resources Section below.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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For information about clinical trials sponsored by private sources, in the main, contact:
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FROM THE INTERNET
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