Botswana study: Climate trends a key to public health plans

In low- and middle-income countries, diarrhea is the second leading cause of death in babies and children younger than five, and the problem is especially acute on the African continent. It is the cause of one-fourth of child deaths there, and scientists say there’s a link to climate conditions. What’s more, they think that knowing the climate patterns can drive advance planning to prevent more deaths.

Researchers at the Columbia University Mailman School of Public Health in the United States know that the El Niño-Southern Oscillation (ENSO) pattern – a cyclical phenomenon of ocean and atmospheric interactions in the equatorial Pacific – deliver the warmer El Niño ocean temperatures and the cooler La Niña waters. They also know its effects on weather patterns, and that previous research established links between El Niño years and diarrhea outbreaks in places like Peru, Bangladesh, China, and Japan.

They also knew that previous studies of ENSO impacts on Africa looked at deadly cholera, with links found in Uganda and the West African Great Lakes region. The problem is that cholera is a specific diagnosis, and there’s research that shows it accounts for just one percent of all diarrhea cases in African children. So they decided to look again with a wider lens during a study in Botswana, a stable middle-income country with access to health care and well-developed water and sanitation systems.

Their findings, published in Nature Communications, were based on nearly 11,000 cases reported across 10 years in the Chobe River region in the country’s northeast and the ENSO cycles across the same time. The results suggest that the cooler temperatures, increased rainfall and flooding associated with La Niña years add up to about a 30 percent rise in the number of childhood diarrhea cases between December and February. They also found up to a seven-month lag time in when those cases emerge, meaning that public health and aid agencies might anticipate the spike when the ENSO cycle first becomes active.

“These findings demonstrate the potential use of the El Niño-Southern Oscillation as a long-lead prediction tool for childhood diarrhea in southern Africa,” says lead author Alexandra Heaney, a former Colombia doctoral student in environmental health who is now at University of California, Berkeley.

“Advanced stockpiling of medical supplies, preparation of hospital beds, and organization of healthcare workers could dramatically improve the ability of health facilities to manage high diarrheal disease incidence.”

The knowledge also could alert public works teams to any strains on the infrastructure that might contribute to waterborne illnesses leading to diarrhea, such as drinking water from the Chobe River source.

The authors note their ENSO findings are specific to the region and illness, but that speaks to a wider point too: If climate patterns driving weather conditions are better understood, they may be a useful locally-focused tool for predicting spikes not only in childhood diarrhea cases but for malaria, flu and other illnesses.