The shifting geography of cholera

El Niño brings drought to the southern hemisphere and floods to its northern counterpart.

Its most recent arrival, spanning 2015 and 2016, resulted in two years of drought throughout Southern Africa.

Millions of people went hungry as crops failed. Yields from South Africa’s critical maize crop halved to seven million tonnes from 14-million.

In East Africa, the phenomenon brought heavy rains and flooding – and more cases of cholera.

New research has found that there are 50 000 more people with cholera across this region in each year that El Niño is around.

According to a team from Johns Hopkins Bloomberg School of Public Health, which publishing its findings in multidisciplinary scientific journal Proceedings of the National Academy of Sciences the number of cholera cases in Southern Africa decreases by 30 000 a year during a drought, because the sewerage systems are able to function better.

When it does rain, sewerage systems are overwhelmed and sewage then flows into rivers and drinking water systems. This results in diseases, including cholera, the symptoms of which are severe vomiting and diarrhoea. If left untreated, up to 30% of cholera patients die.

When it isn’t raining, those polluted water systems and rivers still carry diseases, which people contract because they rely on these rivers for drinking and cooking water, although the likelihood is substantially reduced.

A drop of 30 000 cases is significant but the sudden increase to 50 000 cases is a big jump for countries that are struggling to contain the disease.

World Health Organisation numbers estimate that there are up to four million cholera cases around the world each year, with between 21 000 and 143 000 deaths a year. About 40% of these cases are in Africa.

The Johns Hopkins team looked at satellite data from El Niño years between 2000 and 2014, mapping cholera cases before, during and after each occurrence of the phenomenon.

By rapidly warming the Pacific Ocean, this climate cycle changes global weather far quicker than any other single force.

Climate change projections show that El Niño’s intensity and regularity has already started increasing in a rapidly warming world. This is a problem for countries that already suffer from the consequences of weather-related disasters.

The Johns Hopkins research – titled El Niño and the Shifting Geography of Cholera in Africa – said their findings should help to stop these spikes in the number of cholera cases in the future. Because of its global impact a lot of data is being gathered in the Pacific. El Niño starts its warming there, which means African countries generally have a six-month to one-year warning that it is coming.

This gives governments time to get treatment facilities and medicines in place and to be on alert in the areas likely to be hit by an increase in cholera and other diseases.

“If you have cholera centres available, fast, supportive care can reduce the fatality rate from cholera from as high as 30% to nothing,” according to the Johns Hopkins research.

Sipho Kings
Sipho is the Mail & Guardian's News Editor. He also does investigative environment journalism.
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