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The Facts

Cholera is a bacterial infection of the small bowel that can cause severe diarrhea and dehydration.

There have been seven great pandemics (worldwide epidemics) of cholera in history. The seventh began in 1961, when cholera re-emerged in Indonesia and swept across most of the world, and it still lingers today.

Researchers estimate that each year there are 3 million cases of cholera worldwide, with approximately 100,000 deaths annually.

Cholera settles wherever poor hygiene permits it to infect humans, who appear to be cholera's only hosts. The bacterium that causes cholera is most productive in times of flood and war, since these events can reduce the availability of clean water. Cholera continues to occur in Asia, Africa, the Middle East, and South and Central America. Worldwide, cholera kills about 4% of the people who develop severe symptoms. That includes people who are treated too late or inappropriately and those who never reach a doctor. Fewer than 1% of people with severe cholera die if they're quickly and properly treated.


Cholera is caused by a bacterium called Vibrio cholerae. A person gets cholera by drinking water or eating food infected with the bacterium. Once swallowed, it settles in the lining of the small bowel and releases a toxin (poison) that can cause the body to flush liquid into the small bowel, resulting in watery diarrhea.

The bacterium that causes cholera is usually transmitted by water contaminated with human feces, but it can also be transmitted by ingesting contaminated food, especially raw or undercooked seafood and shellfish. Most people infected with cholera have no symptoms, yet they carry the bacteria for a few weeks, excreting them slowly into the water supply.

Naturally, this isn't a major problem in countries with flush toilets and sewage plants. Canada, the US, and Western Europe rarely report cholera, and if they do, it's almost always seen in someone who has returned from a high-risk country.

Symptoms and Complications

Approximately 25% of people who ingest the bacteria actually develop the particular symptoms that we call cholera. Of those, 80% will experience symptoms that are only of mild or moderate severity, while up to 20% will develop severe watery diarrhea that can be life-threatening if not treated properly. The remainder will have no symptoms whatsoever, although they often excrete the bacteria in their stool, which can spread it to others.

It is not known why some people develop cholera while others are unaffected by the bacterial toxin. Most adults in cholera-endemic areas have some antibodies, which helps to protect them from developing the disease. In these countries, severe symptoms are far more common in children and in those who have some additional underlying disease such as AIDS.

Vibrio bacteria are killed by stomach acid. Research has shown that people with low acidity in their stomach (e.g., people taking antacid medications) are much more prone to cholera. Also, people with type O blood seem to be more at risk.

If symptoms of cholera occur, the main symptom is watery diarrhea, which can be severe enough to rapidly drain the body of vital water, salts, and minerals. The first watery stool appears 1 to 3 days after infection, and from then on the body can lose up to one litre of liquid an hour. Vomiting may appear at the same time.

Other symptoms of severe cholera are:

  • muscle cramps
  • reduced or no urination
  • weakness
  • low pulse
  • sunken-looking eyes
  • wrinkled skin on fingers

Cholera usually runs its course in 3 to 6 days, but if it is not treated it can cause shock from dehydration, kidney failure, coma, and death.

Making the Diagnosis

When symptoms occur, a proper diagnosis is very important because cholera has the potential to cause death from severe dehydration. The diagnosis is made by taking a stool culture, as the bacteria can be seen using a special microscope.

Treatment and Prevention

If you think that you might have cholera, immediately start drinking oral rehydration solutions (made from purified water, sugar, and salts) on your way to the hospital or doctor. To prevent vomiting, drink frequently but drink small amounts. If you do not have access to medical care, self-treat with an antibiotic for travellers' diarrhea.

The basic treatment for cholera is fluid replacement, including salts and minerals. This solution is given either orally, intravenously, or through the nose (by a special tube) into the stomach. Antibiotic pills are often given at the outset and can shorten the diarrhea significantly.

Preventing cholera when you travel may not always be easy. There is an oral vaccine that provides 85% protection for 6 months and about 50% over 2 years. However, cholera is extremely rare among travellers, with an estimated rate of 1 affected person per 500,000 travellers. Therefore, the vaccine may not be routinely recommended by doctors.

Following these precautions in affected areas can improve your chances of preventing cholera:

  • Drink only bottled, boiled, or chemically treated water. Disinfectant tablets are available in pharmacies.
  • Use bottled, boiled, or chemically treated water to wash dishes and brush teeth.
  • Peel all fruit and vegetable skins before eating.
  • Keep flies away from food.
  • Avoid ice cubes (unless they are made from purified water), ice cream, unpasteurized milk, and salads, which can easily be contaminated with bacteria.
  • Cook all foods thoroughly and eat them while they're hot.
  • Be especially careful of shellfish, as they are often a source of vibrio.
  • Avoid ceviche (raw fish that is a local delicacy in Latin America).
  • Avoid foods and drinks from street vendors.
  • Wash hands often with soap and water.

Here's a helpful saying to help you remember these strategies: "Boil it, cook it, peel it, or forget it!"

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