Cholera is caused by the bacterium Vibrio cholerae, a tiny microbe that can infect the intestines. The physical signs and symptoms of cholera aren't caused by the bacterium itself, but rather a toxin it produces once it's inside the body. That toxin disrupts the way cells absorb and process fluids and electrolytes, forcing them to go in just one direction: out.

That's what sparks the body to expel watery diarrhea, the most common symptom of cholera. Vibrio cholerae is highly contagious and is primarily the result of contaminated food, water and, in some cases, the environment.

Common Causes

In order for cholera to spread in a community, it has to be introduced to that community first—either naturally via the environment or, more commonly, because someone who was infected brought it there.

Contaminated Food and Water

Cholera is typically spread via the “fecal-oral” route—that is, through eating food or drinking water that has been contaminated with fecal matter containing the bacteria.

The bacteria hitch a ride out of the body inside human feces or diarrhea, so if someone who is infected goes to the bathroom and then doesn't wash his or her hands before touching food or coming into contact with a water source, it can spread to other people.

The threat of wells or other sources of drinking water becoming contaminated is especially high in developing areas without the infrastructure in place to filter and clean the water. Because Vibrio cholerae is so infectious and most people don't have any symptoms, the bacterium can spread far and wide before health officials are alerted to the outbreak.

This is particularly true in areas where other kinds of diarrheal diseases might also be common, making it less obvious that cholera has been introduced. Similarly, there are still many people in the world without access to sanitation services like toilets or outhouses. In these cases, if infected individuals defecate in the open environment, the bacteria can get into open water sources.

Unsafe food prep is another major cause for concern. Even in developed countries with sound infrastructure, the bacteria can get into food via unclean hands or contaminated water, though outbreaks in these countries are extremely rare. Anyone who eats contaminated food could get sick or—at the very least—spread the bacteria to even more people.

It's important to note that you can shed the bacteria in your feces even if you don't have any symptoms—meaning infected individuals can spread the disease without knowing it. This can last for anywhere from two days to two weeks, depending on the case.

Environmental Sources

In addition to drinking water sources and contaminated food, the bacteria that cause cholera can also live in coastal waters, particularly around the equator and in tropical regions. In rare cases, shellfish can take in the bacteria from their environment.

These germs are often killed during the cooking process, but if you eat the contaminated shellfish raw or it wasn't cooked well enough, you could get infected that way, too. Most cholera outbreaks, however, are caused by poor sanitation.

Healthcare Environments

Occasionally, healthcare personnel treating cholera patients can come into contact with the bacteria, particularly when handling stool samples or other contacts with feces. This, however, isn't as common of a source for outbreaks as contaminated food or water.

In most cases, taking steps to ensure adequate hygiene, sanitation, and clean water supplies is sufficient to prevent the spread of cholera.

Risk Factors

Certain things make you more likely to get cholera, including where you are and what access you have to safe water and sanitation.

Living or Visiting an Endemic Area

You can't get cholera if the bacteria aren't present, so one of the greatest risk factors for getting the disease is visiting a place where it's common. Countries where the bacteria circulates regularly are known as "endemic" countries, and visitors and residents of these places should be extra cautious to keep their hands, drinking water, and food clean.

In these areas, cholera can be seasonal—much like the flu—or sporadic, where outbreaks crop up in different areas throughout the year.

Before taking a trip abroad, it's important to check the Centers for Disease Control and Prevention's website to see if the country you're visiting experiences cholera epidemics.

It's important to understand, however, that places where the disease isn't endemic can still have outbreaks—though they are typically extremely rare and limited in scope.

Poor Environmental Conditions

Because cholera is primarily spread through contaminated food and water, lacking access to safe water and sanitation, as well as proper waste management, can increase the chances of an outbreak happening if someone with cholera enters the area. This is particularly true for urban environments or areas where large groups of people live, eat, and work in close proximity to each other.

How Cholera Is Diagnosed