WASHINGTON United States (Xinhua) --
The geographic distribution of cholera
incidence in Africa changes dramatically during El Nino years, with
the burden shifting from portions of southern, central, and west
Africa to east Africa, a new study suggested Monday.
El Nino, a cyclical phenomenon of warmer water in the equatorial
Pacific Ocean, is associated with increased rainfall in East Africa
and decreased rainfall in southern Africa, west Africa, and parts of
However, little evidence supports a link between cholera outbreaks
and El Nino in Africa, which has the most cholera deaths in the
Cholera is an infectious and often fatal bacterial disease,
typically contracted from infected water supplies and causing severe
vomiting and diarrhea.
In the new study published in the U.S. journal Proceedings of the
National Academy of Sciences, researchers collected data on cholera
cases in Africa from 360 separate data sets, analyzing 17,000 annual
observations from 3,710 different locations between 2000 and 2014.
The total number of cases of cholera across Africa as a whole were
about the same in El Nino years as compared to non-El Nino years,
the researchers found.
But the geographic distribution of illnesses was fundamentally
different, with about 50,000 additional cases in East Africa and
30,000 fewer cases in southern Africa during El Nino years than
during non-El Nino years.
At the same time, parts of central west Africa also saw
significantly fewer cases of cholera.
Overall, 177 million people live in areas where cholera incidence
increased during El Nino years by at least one per 100,000
Within regions where the association between El Nino and increased
cholera incidence was strongest, cholera incidence tripled during El
The findings could allow countries to prepare for cholera outbreaks
long before they start, said study leader Justin Lessler, an
associate professor of epidemiology at the Johns Hopkins University.
“We usually know when El Nino is coming six to 12 months before it
occurs,” he said in a statement. “Knowing there is elevated cholera
risk in a particular region can help reduce the number of deaths
that result. If you have cholera treatment centers available, fast,
supportive care can reduce the fatality rate from cholera from as
high as 30 percent to next to nothing.”
In addition, there is already an approved vaccine for cholera, but
its effects are not lifelong and there are not enough doses for
everyone in areas that could be impacted by El Nino.
Once there is more vaccine, Lessler said, it can be another tool for
health officials to use as they try to prevent deadly cholera in