By the end of this century, malaria could be eradicated in West and Central Africa, two of the worst-affected regions. A modelling study suggests cases will plummet in these areas if the extreme heat caused by climate change makes them uninhabitable for mosquitoes. But this also means malaria is expected to become more pronounced in the cooler regions of Africa.
“The overall story is that the burden is shifting,” says at the University of California, Berkeley.
Climate change is generally associated with worsening infections, as animals like mosquitoes start thriving in regions that were previously too cool for them. But in some cases, excessive heat means the insects can no longer survive in their original habitats.
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Malaria, which caused , occurs when people get bitten by a mosquito infected by a Plasmodium parasite. Laboratory tests indicate between 16°C and 34°C, with malarial transmission highest at 26°C.
Now, Carleton and her colleagues have analysed data published in 2017, which includes information from more than 50,000 surveys of malaria prevalence across sub-Saharan Africa between 1900 and 2016. They have condensed this data into 9875 monthly averages at state or province level, and used different climate simulations to estimate how human-led global warming influenced malaria infections over this time period.
Their results suggest that from 2010 to 2014, human-caused climate change resulted in an additional 1 child per 1000 developing malaria across sub-Saharan Africa, compared with what would have been expected during those years without this warming. These additional infections were most concentrated in West and Central Africa.
Next, the researchers projected future impacts by running the same models under low, intermediate and high greenhouse gas emissions scenarios. Their results suggest that under high emissions – which would lead to about a 2.4 degree Celsius rise in global temperatures – there could be around 45 fewer children per 1000 with malaria in West Africa by 2100, compared with 2015 to 2020. Central African nations like the Democratic Republic of the Congo, meanwhile, could have 16 fewer cases per 1000.
This – combined with existing malaria prevention strategies like vaccines, insecticides and bed nets – may help eradicate the condition from these areas, says Carleton.
But the team’s results also suggest that malaria prevalence will rise in cooler or high-elevation areas, including parts of Kenya, Burundi, Angola, Zambia and northeastern South Africa. These areas have had less investment in malaria prevention strategies, says Carleton. They will probably also have fewer people with to these parasites.
“This is a meticulous paper that leverages good new data,” says at Victoria University of Wellington in New Zealand. “Ultimately, however, it finds that climate is only of second-order effect in determining malaria prevalence. By far more important are public health investments. Elimination requires a functioning health system so infected individuals do not continue the chain [of transmission].”
Global efforts to reduce emissions could curb these regional rises in cases, says Carlton. “The blessing, or curse, with CO2 is that abating a ton of CO2 has the same impact on the global climate, no matter where you do it,” she says. “So, whether we’re curbing emissions in Beijing or New York, we have the potential to generate benefits, particularly for Africa and parts of the Global South.”
at the University of Florida says this “really elegant study” pulls together various types of data to project the impacts of climate change. “Overall, it’s sad to see such stark evidence of climate-driven shifts”, especially given our capacity to mitigate this, she says.
Nature
