A malaria researcher testing blood samples at the Noguchi Medical Institute of the University of Ghana. Image: Gates Foundation/Flickr
Thanks to warming climates, malaria will likely spread its influence to places where it hasn’t been a problem before. That means the burden of treating one of the world's most resilient illnesses will shift to locales that aren't necessarily ready.
According to a team of researchers at the University of Liverpool, tropical highlands in east Africa, Central America, and Southeast Asia will begin to see the disease show up more often as the mosquito that transmits it begins to be able to survive there.
Malaria, more than most diseases, is closely pegged to climate. Weather, combined with urban and economic development, swampland destruction, and pesticide application, led to the eventual eradication of malaria in places like the United States and Western Europe. But shifting climates is going to both lengthen malaria seasons in certain parts of the world and may even bring the disease to places that have otherwise seen limited burden from it.
It’s not a perfect comparison, but similar climate-driven disease expansion has been seen in things such as coffee, where a virus known as coffee rust or “roya” has expanded into the highlands of Colombia and Central America, places that were once too cold for it to exist.
According to Andrew Morse, one of the researchers that worked on the study published in Proceedings of the National Academy of Sciences, the aforementioned regions—along with South Africa, central Angola, the plateaus of Madagascar, southern Brazil, eastern Australia, and the border between India and Nepal—are expected to see longer malaria seasons. West Africa, India’s coasts, northern Australia, Malaysia, and South America as a whole are expected to see shorter malarial seasons.
The projected change in the length of the malaria transmission season (LTS) in months, based on various climate models. Image: Caminade et. al
In Africa, the “net effect” is expected to be small, with malaria burden being shifted southeast from western Africa.
Determining whether climate change has already had an effect on malaria’s range is difficult, because good historical records of malaria cases don’t exist. Within the last decade or so, African health ministries have begun to keep closer tabs on the disease, so moving forward, it will be easier to determine whether climate is truly playing a role in the disease’s expansion or decline.
“The quality records, if they’re available, only go back five or 10 years,” Morse said. “But now, they’re using more sophisticated detection techniques, they’re looking at the genomes of the parasites. If these countries can keep these programs funded and running for 20 years, we’ll have a good picture of what happened.”
The model doesn’t take into account the fact that intervention efforts are making a very real impact in malaria rates all around the world. Bed net programs, economic development, and better drug availability drove down the number of malaria deaths by 45 percent globally and 49 percent in Africa between 2000 and 2012, according to the World Health Organization. But the disease is still one of the world’s greatest killers. In 2012, roughly 627,000 people died from the disease.
“In some areas that have good health prevention measures, malaria might not appear even though it’s shown in the models,” Morse said.
And that’s the point. Morse said his study isn’t meant to be be alarmist, and that he hopes it’s used by countries to start preparing intervention methods now.
“We want this to be useful for decision makers. We expect to see a climate-driven emerging risk in these areas, and they should be aware of it and not be complacent,” he said. “They can start to put interventions in place now to reduce that emerging risk."