For decades, cholera has been one of Africa’s most persistent public health threats. The disease, caused by drinking contaminated water or eating contaminated food, can kill within hours if left untreated. It is especially dangerous in places where clean water, proper toilets, and medical care are in short supply.
A study published in Nature Medicine reveals something both surprising and troubling: while the average rate of cholera across Africa has stayed about the same over the past decade, the places where it hits hardest have shifted dramatically.
Researchers from Johns Hopkins University and partners across Africa examined more than 30,000 health reports from 43 African countries between 2011 and 2020. They combined this data with detailed maps, dividing the continent into squares just 20 kilometers wide. This allowed them to pinpoint changes in cholera “hotspots”, areas with unusually high numbers of cases.
A decade of change
From 2011 to 2015, western Africa carried much of the continent’s cholera burden. Countries like Guinea, Sierra Leone, Ghana, and Nigeria saw frequent outbreaks, often fueled by poor sanitation and contaminated coastal waters.
But between 2016 and 2020, the picture changed dramatically. Cholera rates dropped sharply in much of western Africa yet rose steeply in eastern and central Africa. Ethiopia, Sudan, the Democratic Republic of Congo, and parts of Tanzania and Uganda saw outbreaks grow in size and frequency.
A growing population at risk
By 2020, an estimated 296 million people in Africa, more than one in four, lived in areas with high cholera rates. Of these, 82 million were in “very high incidence” zones, with at least 100 cases per 100,000 people each year.
One of the most striking findings was how quickly risk levels could change. About 135 million people were living in areas with low cholera risk between 2011 and 2015 but high risk just five years later.
Unpredictable and persistent
The study also revealed how unstable cholera patterns can be. Some areas suffer high rates year after year, the Democratic Republic of Congo, for example, reported large outbreaks every year in the decade studied. Other places might go years without cases and then see sudden flare-ups.
Ghana is a recent example: after eight years without a major outbreak, cholera returned in 2024. The researchers found that even areas with no cases for a decade still have about an 11% chance of seeing cholera again in the near future.
The reasons for these shifts are complex. In some places, improved water, sanitation, and health systems have reduced cholera risk. In others, conflict, population displacement, floods, and droughts have worsened it. Climate change, which can cause both water shortages and flooding, may also play a role.
Targeting the right places
For years, global health agencies have urged countries to target cholera control efforts at “hotspots”, areas with the worst recent outbreaks. That might include mass vaccination campaigns, improvements to water and sanitation infrastructure, and rapid-response teams to contain new cases.
But this study warns that relying on old outbreak maps can miss the mark. If you target the areas that were worst hit five or ten years ago, you may miss many of today’s highest-risk communities.
The researchers found that targeting the 10% of Africa’s population living in the highest-burden areas based on current data could reach more than 60% of cholera cases. But if you target based on data from five years earlier, you might only reach about 37% of cases.
Even if you know where to target, there’s another challenge: vaccine supply. The oral cholera vaccine (OCV) is safe and effective, but global production is limited about 37 to 50 million doses in 2024, far fewer than needed to protect all high-risk communities.
Because of shortages, the World Health Organization has at times cut its recommended two-dose vaccination course to a single dose during outbreaks, even though protection doesn’t last as long. This makes it all the more important to use the available doses where they will have the biggest impact.
What needs to happen next
The researchers say the best strategy is to focus on areas with either very high recent cholera rates or consistently high rates over a long period. These areas are most likely to keep seeing outbreaks and would benefit most from investment in vaccines, clean water, sanitation, and health services.
But they also warn that no place is completely safe until access to clean water and sanitation is widespread. Areas without recent outbreaks can still see cholera return suddenly, especially if the bacteria are reintroduced.
Takeaway
The big takeaway from this study is that cholera in Africa is not static. The disease is shifting geographically, often unpredictably, and sometimes in ways that catch countries off guard.
IMAGE OF THE WEEK
Constantine the African (c. 1010–1087), originally from Tunisia in North Africa, traveled to Europe and played a key role in translating Arabic medical texts into Latin. His work, including translations of Galen and Avicenna, helped revive medical science in medieval Europe and influenced generations of physicians.
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