Cholera is a severe diarrheal disease that is deadly without treatment. Thanks to modern hygienic advances, such as clean sanitation systems and drinking water, the disease is rare in the US and other developed countries.

Even though cholera is easily prevented and treated, it remains a huge public health problem in countries where hygienic practices and sanitation systems are not established. For example, the cholera epidemic in parts of Africa has been ongoing for more than 30 years, due to inadequate sanitation and water treatment systems.

Species Name:

Vibrio cholerae

Type of Microbe: Gram-negative bacteria

How it spreads: Transmission usually results from consuming water that is contaminated with feces from an infected person. Consumption of cholera can happen through drinking contaminated water or eating foods that have been washed with or made with contaminated water. This kind of water-borne transmission is common in areas with poor sewage systems and unclean drinking water. Foodborne transmission may also occur when an individual eats raw or undercooked shellfish. For example, people in the US have occasionally contracted cholera from eating undercooked shellfish from the Gulf of Mexico. Person-to-person transmission is unlikely.

Who’s At Risk? 

The largest outbreak in the last 5 years has been in Haiti. This was introduced from Nepal in 2010. This occurred when there was an outbreak in Nepal and UN Nepalese troops in Haiti were being rotated.

This was a novel introduction and not related to the earthquake; the troops were not responding to the earthquake. Around 9000 died; 700,000 infected in a country with a little over 10 million people. The bacteria also spread, in small outbreaks, to the Dominican Republic, Cuba, and Mexico.

Outbreaks also have occurred in Eastern and Western Africa.

There was an outbreak in the 1990's in Latin America, which was first identified in Peru in January 1991 after introduction there. Outbreaks are sometimes replaced to displacements of people who then do not have toilets or safe water sources. To arrive somewhere new where it is not already found in the water, however, the bacteria has to be carried there. Without the introduction, the bacteria, if not already there, will not be there.

Individuals living in or traveling to developing countries are those most at risk. Cholera is rare in the US, with only 0 to 5 cases occurring every year. Cases imported to the US are not usually a worry as the disease can be treated with rehydrated and toilets and good sanitation and clean water prevent spread.


Within 6 hours to 5 days of exposure, symptoms range from being mild or asymptomatic to severe disease, characterized by huge volumes of explosive watery diarrhea (sometimes called "rice water stools" because of the similarity of appearance to water that has been used to wash rice), vomiting, and leg cramps.

Due to rapid loss of fluids (up to 20 liters daily), severe dehydration and shock can occur in these individuals. Signs of dehydration include loss of skin plasticity, sunken eyes, fast heart beat, low blood pressure, and rapid weight loss. Shock occurs as a result of collapse of the circulatory system in those who are not rehydrated. There is usually no fever. 


Clinical symptoms of profuse watery diarrhea. There is usually no fever. "Cholera cots", cots with openings to allow fecal output into a bucket, are used to measure volumes of stool loss and fluid replacement needs. Consider the diagnosis in all cases of severe watery diarrhea and vomiting especially with rapid dehydration and recent travel or consumption of shellfish. Lab tests include stool gram stain (gram negative rods) culture, dark field microscopy or stool PCR. People must begin treatment even before diagnostic work-up.


Most infections are not severe, with 75% of infected people not showing any symptoms. However, these individuals continue to shed the bacteria back into the environment, potentially infecting others with severe cholera disease. In these individuals, the large volume of diarrhea helps to wash out the bacteria, allowing the infection to resolve spontaneously. However, because of severe dehydration, fatality rates are high (25 to 50%) when untreated, especially among children and infants. Death can occur in otherwise healthy adults within hours. Those who recover usually have long-term immunity against reinfection.


Because death from cholera is a consequence of dehydration, the disease is treated using oral rehydration therapy (ORT), which consists of large volumes of water mixed with a blend of sugar and salts. Prepackaged mixtures are commercially available, but wide distribution in developing countries is limited by cost. Therefore, homemade ORT recipes using common household ingredients and materials have been developed. Severe cases of cholera require intravenous fluid replacement. Antibiotics can shorten illness, but ORT is still necessary even when antibiotics are used. Do not use anti-diarrheal medicines, since they prevent flushing of the bacteria out of the body.

Others are treated with IV fluids if they are unable to drink enough ORT.


The CDC recommends to “Boil it, cook it, peel it, or forget it”. Individuals living or traveling to places where cholera is found should drink boiled or chlorine- or iodine-treated water or bottled beverage. Foods should be thoroughly cooked, and individuals should peel their own fruits. Also, avoid ice, raw foods, and ice cream. Be wary of foods and beverages from street vendors.

A new oral vaccine, called Dukoral is available in other countries, but is not available or licensed in the US. Its protection is not life long and is not complete.

How it causes disease:

The bacteria attach to the small intestine and produce a toxin that disrupts the control and balance of fluid retention of mucosal cells within the intestines. Again, it generally does not cause a fever; the bacteria remain in the intestines.


Cholera. Division of Foodborne, Bacterial and Mycotic Diseases. Centers for Disease Control and Prevention

Cholera. World Health Organization.

Vibrio cholerae Serogroup O1. USFDA Bad Bug Book. Center for Food Safety and Nutrition.

Cholera - Public Health England

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