Cholera has an interesting connection to the development of the field of public health. Between 1853-1854, many people in London became ill with cholera. At the time, people did not know what was causing the illness. Two theories existed. Some people thought the disease was spreading through the air; this was called the “miasma theory.” Others, including a doctor named John Snow, thought it was caused by something in the water; this was called the “germ theory.” 

Dr. Snow started studying who was becoming sick and where they lived. He found that most of the people who died got their water from a specific water pump located on Broad Street in London. In contrast, inmates from a nearby workhouse and workers from a nearby brewery did not experience similar death rates. Both of these locations used water from other sources. Snow asked authorities to remove the handle from the water pump. The outbreak ended, providing evidence that the illness was being caused by something in the water not the air. Dr. Snow’s findings also contributed to our understanding of germ theory, which ultimately prevailed as we learned that infections are caused by specific pathogens.

Because of his analytical approach to figuring out the cause of the outbreak, Dr. Snow is often considered the father of epidemiology.

The disease

What is cholera?

Cholera is caused by a bacterium, known as Vibrio cholerae. The bacteria attack the small intestine. About 5 of every 100 infected people experience diarrhea as their intestine struggles to absorb excess fluids produced as a result of the infection. Sometimes, diarrhea and subsequent loss of fluids can be so severe that people go into shock and die.

What are the symptoms of cholera?

Many people with cholera do not experience symptoms or only have mild diarrhea. Those with more severe disease can quickly become dehydrated as a result of frequent diarrhea and vomiting. Because of the rapid loss of fluids, patients can experience other complications, such as: 

• Mineral imbalances
• Kidney failure
• Arterial blockages

Expectant mothers can experience premature delivery or miscarriage. 

People with severe disease can be treated with rehydration therapy, the introduction of fluids and electrolytes to restore mineral balance and hydration. This therapy can be given by mouth, but in severe cases, it is most effective when given intravenously (IV). In the absence of rehydration therapy, about 4 of every 10 people with severe disease die from the illness.

How do you catch cholera?

Cholera bacteria may be present in contaminated food, water or shellfish. Shellfish contain cholera for the same reason that they contain hepatitis A virus. Both cholera and hepatitis A viruses are found in water. Because shellfish filter hundreds of quarts of water each day in their search for food, they actually collect and concentrate cholera and hepatitis A viruses.

Travelers are generally not at risk of cholera if they: 

• Stay in areas with standard tourist accommodations.
• Eat only cooked shellfish and cooked food.
• Practice good hygiene.
• Drink bottled water.

How common is cholera?

Rates of cholera are difficult to determine for a couple of reasons:

1. Many people do not experience symptoms, so they do not seek medical care. This leads to underreporting.
2. Since the spread of cholera is partly due to sanitation levels, the disease can occur in two different situations. First, it can be an ongoing concern where sanitation standards are low, such as in developing countries. This is called an endemic. Second, it can become a concern in areas where infrastructure that maintains sanitation has been damaged, such as by natural disasters or war. This is called an epidemic or outbreak. 

Climate change is also contributing to rates of cholera, particularly as increases in rainfall and flooding affect water cycles and sources.

It's estimated that each year about 4 million cases and about 143,000 deaths are caused by cholera. In 2024, 98% of cases occurred in Africa, the Middle East and Asia. The small number of cases that occur in the U.S. are typically the result of travel to areas that have disease or from eating undercooked shellfish, such as crabs.

Where can you catch cholera?

Cholera is common in several countries or regions of the world. To learn more about where cholera is occurring, consult this map from the European Centre for Disease Prevention and Control. The World Health Organization offers additional information about cholera.

How can I protect myself and my family?

If you are traveling to a country where cholera is occurring, follow safe food and water precautions:

• Drink only bottled or treated water.
• Do not consume raw or undercooked foods, especially seafood.
• Practice diligent handwashing before eating and after using the bathroom.

The vaccine

Is there a cholera vaccine?

Yes. A number of cholera vaccines have been made, but vaccination is not commonly recommended. The vaccines are safe, but two factors relate to the limited use:

• The risk of disease, even to travelers, is low. 
• The immune response to the vaccine is short-lived. 

In 2016, Vaxchora was approved in the U.S. for adults 18 to 64 years of age traveling to cholera-affected areas. Approval has since expanded to allow for use in children starting as young as 2 years of age.

The vaccine is approved for one dose in the U.S.

How is the cholera vaccine made?

The vaccine is made by taking the bacteria and weakening it so that it can’t reproduce itself very well. The live weakened vaccine is given as a single dose taken by mouth. It doesn’t cause disease. Five cholera vaccines are available throughout the world, but vaccine supplies have been limited.

Does the cholera vaccine have side effects?

People who receive the oral cholera vaccine used in the U.S. may experience nausea, vomiting or diarrhea.

Who should get the cholera vaccine?

The cholera vaccine is generally not required or recommended for travel anywhere in the world, with a few exceptions based on whether cholera is spreading. 

The vaccine should be given at least 10 days before travel, and the person should not eat or drink for one hour before or after getting the vaccine.

Other questions you might have

Why do I need a hepatitis A vaccine but not a cholera vaccine if both can be transmitted in contaminated water and shellfish?

Hepatitis A virus infections are less related to sanitation levels, so they occur even in places with standard tourist accommodations. Also, it is easier and less expensive for countries to eliminate cholera bacteria from water than to eliminate hepatitis A virus from water.

Relative risks and benefits

Do the benefits of the cholera vaccine outweigh its risks?

Although the cholera vaccine does not have serious side effects, most travelers are not at high risk of catching cholera if they stay in standard tourist accommodations. So, for most people, the cholera vaccine isn't necessary.

However, people to areas where cholera is common and who engage in high-risk activities, such as eating raw or undercooked food (such as shellfish) or drinking unbottled water, should get the cholera vaccine.  In these cases, the benefits outweigh the risks.

Disease risks

• Diarrhea (5 of 100 infected people)
• Severe diarrhea can lead to dehydration, shock and death

Vaccine risks

• Nausea or vomiting
• Diarrhea

References

Orenstein WA, Offit PA, Edwards KM and Plotkin SA. Cholera Vaccines in Plotkin's Vaccines, 8th Edition. 2024, 211-224.

European Centre for Disease Prevention and Control. Cholera worldwide overview.