Cholera is a bacterial infection of the small intestine that causes severe, watery diarrhea and can lead to life-threatening dehydration within hours. It’s caused by the bacterium Vibrio cholerae, which spreads through contaminated water and food. In 2024, more than 560,000 cases and over 6,000 deaths were reported across 60 countries, up from 535,000 cases the year before.
How Cholera Spreads
Vibrio cholerae lives naturally in aquatic environments, particularly in brackish and coastal waters. It becomes dangerous when it enters the human digestive system. Transmission happens primarily through drinking water or eating food contaminated with the bacteria. Within households, cholera can spread through shared food, contaminated water sources, and possibly close contact with an infected person. On a larger scale, outbreaks typically stem from contaminated rivers, lakes, or municipal water supplies, especially in areas with limited sanitation infrastructure.
The bacterium thrives in warm water and can persist in the environment between outbreaks. This is why cholera tends to resurface in the same regions, particularly during rainy seasons or after natural disasters that disrupt clean water access. Countries in sub-Saharan Africa and parts of South Asia face the highest burden, though outbreaks can occur anywhere sanitation breaks down.
What the Bacteria Do Inside Your Body
Once swallowed, the bacteria colonize the lining of the small intestine and release a toxin. This toxin locks a signaling switch inside intestinal cells into the “on” position, which forces the cells to pump chloride (a component of salt) out into the intestinal space. At the same time, the toxin blocks those cells from reabsorbing sodium. The result is a massive buildup of salt in the intestine, and water follows the salt by osmosis, flooding the gut with fluid.
This is why cholera diarrhea is so extreme. Your intestinal cells are essentially acting like open faucets, pouring water and electrolytes into the gut faster than your body can reclaim them. The bacteria themselves don’t invade or destroy the intestinal tissue. All the damage comes from this one toxin hijacking normal cell chemistry.
Symptoms and Timeline
Symptoms typically appear two to three days after exposure, though they can show up anywhere from a few hours to five days later. The hallmark symptom is profuse, watery diarrhea that’s often described as “rice-water stool” because of its pale, milky white appearance. Vomiting frequently accompanies the diarrhea, and together they can drain liters of fluid from the body in a single day.
Most people infected with cholera experience only mild to moderate symptoms, and some have no symptoms at all. But in severe cases, dehydration sets in rapidly. Signs include a racing heart rate, low blood pressure, dry mouth and mucous membranes, and loss of skin elasticity (if you pinch the skin on the back of your hand, it stays tented instead of snapping back). Without treatment, severe dehydration can become fatal within hours.
How Cholera Is Diagnosed
The gold standard for confirming cholera is a stool culture, where a lab grows the bacteria from a stool sample and identifies it through serotyping. Molecular methods like PCR can also confirm the diagnosis. During active outbreaks, rapid diagnostic test kits offer quicker results in the field, but they have limitations. They can’t provide a bacterial sample for testing which antibiotics will work, so they’re used as a screening tool in epidemic settings rather than for routine diagnosis.
Treatment: Rehydration First
The cornerstone of cholera treatment is replacing lost fluid and electrolytes. For most patients, this means oral rehydration solution, a precise mixture of salts, sugar, and water that the intestine can still absorb even during active cholera. The WHO-recommended formula contains 75 millimoles each of sodium and glucose per liter, along with potassium and citrate, at a total concentration slightly lower than blood plasma. This specific balance maximizes water absorption through the gut wall.
For children, zinc supplements (20 mg daily for 10 to 14 days, or 10 mg for infants under six months) help shorten the episode and reduce the risk of recurrence for the following two to three months.
Severe cases that involve shock or an inability to drink require intravenous fluids. Antibiotics are reserved for the most serious infections, where they help reduce the volume of diarrhea and shorten the illness. The first-line options include doxycycline, azithromycin, and ciprofloxacin. However, antibiotic resistance is a growing concern. Strains in parts of sub-Saharan Africa and South Asia have shown resistance to several commonly used antibiotics, which makes lab testing of individual samples increasingly important for guiding treatment.
Vaccines and Prevention
Three oral cholera vaccines are prequalified by the WHO. One, called Dukoral, is used mainly for travelers and provides protection for about two years with a two-dose course. The other two, Shanchol and Euvichol (essentially the same vaccine made by different manufacturers), are given to anyone over age one and provide protection for three years after two doses, with at least two weeks between doses. Children aged two to five need a third dose. A single dose of Shanchol or Euvichol offers shorter-term protection, which makes it useful during outbreak responses when vaccine supply is limited.
Vaccination works best alongside the fundamentals: access to clean drinking water, proper sanitation, and safe food handling. Boiling or treating water, washing hands thoroughly, and avoiding raw or undercooked shellfish in affected areas all reduce the risk of infection. In outbreak zones, these basic measures remain the most effective line of defense.
Why Cholera Persists
Cholera is sometimes called a disease of poverty, and the numbers bear that out. Outbreaks cluster in regions where conflict, overcrowding, or underfunded infrastructure leaves people without reliable clean water. Refugee camps, urban slums, and disaster-affected areas are especially vulnerable. The bacterium’s ability to survive in natural water systems means it can’t simply be eradicated. Instead, it waits for conditions that allow it to cycle back into human populations. The steady rise in global cases, from 535,000 in 2023 to over 560,000 in 2024, reflects ongoing gaps in water and sanitation access across dozens of countries.