Cholera is a serious infection of the intestine that is caused by the bacteria Vibrio cholerae and that causes severe diarrhea.
Several species of Vibrio bacteria cause diarrhea (see see Diarrhea in Adults). The most serious illness, cholera, is caused by Vibrio cholerae. Cholera may occur in large outbreaks.
Vibrio cholerae normally lives in aquatic environments along the coast. People acquire the infection by consuming contaminated water, seafood, or other foods. Once infected, people excrete the bacteria in stool. Thus, the infection can spread rapidly, particularly in areas where human waste is untreated.
Once common throughout the world, cholera is now largely confined to developing countries in the tropics and subtropics. It is common (endemic) in parts of Asia, the Middle East, Africa, and South and Central America. Small outbreaks have occurred in Europe, Japan, and Australia. In the United States, cholera can occur along the coast of the Gulf of Mexico.
In endemic areas, outbreaks usually occur when war or civil unrest disrupts public sanitation services. Infection is most common during warm months and among children. In newly affected areas, outbreaks may occur during any season and affect all ages equally.
For infection to develop, many bacteria must be consumed. Then, there may be too many for stomach acid to kill, and some bacteria can reach the small intestine, where they grow and produce a toxin. The toxin causes the small intestine to secrete enormous amounts of salt and water. The body loses this fluid as watery diarrhea. It is the loss of water and salt that causes death. The bacteria remain in the small intestine and do not invade tissues.
Because stomach acid kills the bacteria, people who produce less stomach acid are more likely to get cholera. Such people include young children, older people, and people taking drugs that reduce stomach acid, including proton pump inhibitors (such as omeprazole) and histamine-2 (H2) blockers (such as ranitidine). People living in endemic areas gradually acquire some immunity.
Most infected people have no symptoms. When symptoms occur, they begin 1 to 3 days after exposure, usually with sudden, painless, watery diarrhea and vomiting. Usually, fever is absent.
Diarrhea and vomiting may be mild to severe. In severe infections, more than 1 quart of water and salts is lost per hour. The stool looks gray and has flecks of mucus in it. Within hours, dehydration can become severe, causing intense thirst, muscle cramps, and weakness. Very little urine is produced. The eyes may become sunken, and the skin on the fingers may become very wrinkled. If dehydration is not treated, loss of water and salts can lead to kidney failure, shock, coma, and death.
In people who survive, symptoms usually subside in 3 to 6 days. Most people are free of the bacteria in 2 weeks. The bacteria remain in a few people indefinitely without causing symptoms. Such people are called carriers.
Doctors take a sample of stool or use a swab to obtain a sample from the rectum. It is sent to a laboratory where bacteria can be grown (cultured). Identifying Vibrio cholerae in the sample confirms the diagnosis.
Blood and urine tests to evaluate dehydration and kidney function are done.
Purification of water supplies and appropriate disposal of human waste are essential. Other precautions include using boiled or chlorinated water and avoiding uncooked vegetables and undercooked fish and shellfish. Shellfish tend to carry other forms of Vibrio as well.
Several vaccines for cholera are available outside the United States. These vaccines provide only partial protection for a limited time and therefore are not generally recommended. New vaccines are currently being tested.
Rapid replacement of lost body water and salts is lifesaving. Most people can be treated effectively with a solution given by mouth. These solutions are designed to replace the fluids the body has lost. For severely dehydrated people who cannot drink, a salt solution is given intravenously. In epidemics, if the intravenous solution is not available, people are sometimes given a salt solution through a tube inserted through the nose into the stomach. After enough fluids are replaced to relieve symptoms, people should drink at least enough of the salt solution to replace the fluids they have lost through diarrhea and vomiting. Solid foods can be eaten after vomiting stops and appetite returns.
People are usually given an antibiotic to reduce the severity of diarrhea and make it stop sooner. Also, people who take an antibiotic are slightly less likely to spread the infection during an outbreak. Tetracycline or doxycycline is effective in adults, unless the bacteria in the area are resistant to tetracycline. Then, ciprofloxacin can be used. Because tetracycline and doxycycline discolor the teeth in children under 8 years old, azithromycin, erythromycin, or trimethoprim-sulfamethoxazole is used instead.
More than 50% of untreated people with severe cholera die. Less than 1% of people who receive prompt, adequate fluid replacement die.
Last full review/revision September 2008 by Matthew E. Levison, MD