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Cholera 101: Why this ancient disease is making headlines in 2022

The figure at left is the personification of cholera, facing resistance from a group of women. This 19th century engraving is from Barcelona.
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The figure at left is the personification of cholera, facing resistance from a group of women. This 19th century engraving is from Barcelona.

Updated October 21, 2022 at 10:28 AM ET

Editor's note: This story was republished on October 21 to include new information on current cholera outbreaks and vaccine rationing.

This has been a devastating year on the cholera front.

The World Health Organization states that 29 countries have reported cases of cholera this year — a notable increase from the average of fewer than 20 countries with outbreaks over the past five years. In addition, the fatality rate has almost tripled from roughly 1% to around 3%, prompting increased concern.

In recent years, the annual death toll from cholera has been about 100,000.

Several of those countries have not reported any cases of cholera in years. Lebanon, which had been cholera free since 1993, has reported 18 cases this year. And in Haiti, which hadn't reported a cholera case in over 3 years, Doctors Without Borders teams in Port-au-Prince report they are treating an estimated 100 patients daily.

And now there are issues with the vaccine supply. Because of a limited supply of vaccines, the International Coordinating Group (ICG) — a group that manages vaccine supplies and is comprised of members from the WHO, Doctors Without Borders, UNICEF, and the Red Cross — has temporarily suspended the two-dose cholera vaccination strategy in favor of a single-dose.

The director general of WHO, Tedros Adhanom Ghebreyesus, says, "The one-dose strategy has proven effective in previous outbreaks. Though evidence on how long protection lasts is limited."

A single-dose regiment of the cholera vaccine does not provide immunity against the disease for as long as a two-dose regiment and is less effective at providing immunity to children. However, the change in vaccination strategy is meant to allow more people to be vaccinated during the current outbreak and at a time when the supply of cholera vaccine is extremely limited.

So far this year, 24 million doses of the cholera vaccine have shipped, and 8 million additional doses have been approved for emergency usage in 4 countries affected by the outbreak. WHO says that this change in vaccination strategy is only a short-term solution and that urgent action is needed to increase global vaccine production.

This rise in cholera cases and vaccine news is a reminder that an ancient disease – and one which is easily treatable and preventable — can still take a terrible toll in modern times.

Fast killer

Cholera can kill a person in a matter of hours.

It's a severe gastrointestinal disease, transmitted by a bacterium called Vibrio cholerae. And it can trigger so much diarrhea and vomiting that patients can rapidly become dehydrated. They can lose so much fluid that their internal organs shut down.

The water-borne disease has been around for centuries, and it remains a global health risk. According to the World Health Organization, there are 1.3 to 4 million cases and between 21,000 and 143,000 deaths from cholera each year.

Cases crop up throughout the world — particularly when a crisis or conflict strikes and clean drinking water is not available. Cholera often spreads when someone ingests water or food that has been contaminated by the bacteria; it often enters the water from the diarrhea of someone who is infected.

Climate and conflict

There are two main types of cholera outbreaks: those that circulate within countries where outbreaks happen regularly, and those that begin spiraling out of control during a crisis, such as a conflict or natural disaster like a flood or an earthquake.

In war zones like Ukraine, the breakdown of water, sanitation and health infrastructure means that the introduction of cholera can spread rapidly — and disastrously.

"As those infrastructure systems crumble in conflict, we can have sewage contamination of our water supply, and then our water supply can be a vehicle to transmit cholera," Lantagne says.

During its civil war, for example, Yemen had the worst cholera outbreak in recorded history with more than 2.5 million cases and around 4,000 deaths. The outbreak first struck Yemen back in 2016 and only began tapering in recent months, especially as the prolonged conflict moved into a cease-fire and humanitarian workers were able to restart cholera vaccination campaigns.

Meanwhile, natural disasters — which can affect clean water supply — are becoming more common due to climate change. Floods, for example, pollute water, while drought dries up safe drinking water sources.

That puts people fleeing areas destroyed by climate disasters at higher risk of exposure to cholera. "Any time you get people moving around, and people having to use water that is not their normal water supply, there's likely to be a risk," says Dr. David Sack, a professor of international health at the Johns Hopkins Bloomberg School of Public Health. People on the move may need to drink contaminated water from rivers or other water sources.

And in places where people haven't encountered cholera before, or haven't had recent cases, they have little to no immunity from prior cases or vaccination.

Ancient history

Even though cholera is making headlines in 2022, it's hardly a new disease.

"It's been in the Ganges delta from time immemorial," says Sack, who's spent much of his career studying the disease. Cholera began spreading from India throughout the West in the early 1800s with more global trade and travel by ships, he explains, with cases cropping up from Russia and Western Europe to Baltimore, New York and Philadelphia.

"It was a disease that affected large parts of the world," he says. And it killed millions of people as it spread across the globe. Left untreated, cholera has a fatality rate of about 50%.

"At that time, we didn't know what caused it," says Sack. "We didn't know how to treat it."

Theories about the cause of the illness were plentiful. The leading suspect was the foul air rising from sewers and piles of rotting trash in cities; poison from the soil was another possible culprit. Others looked higher up for a cause: Some faith leaders said it was retribution by God for sinful behavior.

Nearly all of the theories had a common thread, though. There appeared to be a link between cholera and overcrowded urban areas.

Finally, in the 1850s, an English doctor named John Snow became a legend of public health for figuring out that an outbreak in the Soho neighborhood of London was linked to a single drinking water source. Snow is credited with stopping the raging outbreak, which claimed 10,000 lives across London, by taking the handle off of the Broad Street water pump.

Snow argued correctly that water contaminated with sewage was spreading the illness from one resident to another. But he still didn't know exactly what the water was contaminated with; at the time, the pathogen that caused cholera hadn't yet been discovered. He theorized that it might be tiny parasites or germs or some "poison" able to reproduce in the water.

Around the same time, an Italian scientist, Filippo Pacini, identified the bacteria that causes cholera. But his discovery wouldn't be widely accepted for decades — and in the meantime, millions more died.

Souped-up sugar water

"The good news about cholera is that treatment is actually very simple: It's rehydration," Lantagne says.

Cholera is a treatable disease — as long as the patient gets medical attention quickly.

"A patient with cholera should never die," Sack says. "If they get to a treatment center in time, if they still have a breath, we can save their life."

Treatment consists of simply keeping the person hydrated. If they are capable of drinking, they can be treated with oral rehydration fluids — basically souped-up sugar water, like Pedialyte. This strategy works in about 80% of cholera cases. In more severe cases, the patient may need to be given fluids intravenously alongside antibiotics.

If cholera is treated quickly – within hours, before a patient's health declines — fewer than 1% of patients die.

Cholera is also fairly easy to identify. Patients have distinctive stool that is yellowish or whitish – kind of like the color of water that rice is cooked in.

And there are rapid tests that can check for suspected cases in individuals even before a laboratory confirms an outbreak.

There are also three vaccines that can be administered in areas where cholera happens regularly, or when an epidemic begins to take root. More than 30 million people have been immunized since the oral vaccines were developed in the late 1980s.

Yet the vaccine supply is still inadequate, mainly because it has not been seen as a funding priority for other countries. "We don't have enough [vaccines] for every place," Sack says. And it is difficult to venture into conflict zones, like the one in Ukraine, to vaccinate people.

But the vaccine itself is very easy to administer, and it only costs about $1.30 per dose — which means, with enough resources, everyone at risk could be vaccinated.

Another major challenge beyond vaccination is access to safe water and good sanitation — both key to preventing outbreaks. Otherwise, cholera persists even after an epidemic begins to slow.

Melody Schreiber (@m_scribe on Twitter) is a journalist in Washington, D.C., and editor of What We Didn't Expect: Personal Stories About Premature Birth.

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Melody Schreiber
Jason Beaubien is NPR's Global Health and Development Correspondent on the Science Desk.