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As the climate changes, malaria might spread into new areas or return to places from where it was previously eradicated
Fever, nausea, chills: malaria is a disease that affects as many as 198 million people each year. Tragically, 600,000 people, usually children, die.
As the climate changes, malaria might spread into new areas or return to areas from where it was previously eradicated.
“Malaria needs rain on a regular basis, every few days, and it needs to be hot with an average daily temperature of more than 18 degrees Celsius and better for transmission in the mid 20s. These are typical conditions in tropical regions in the rainy season,” said Andy Morse, from the University of Liverpool who will be outlining his team’s methods and projections of malaria and Rift Valley Fever at the Our Common Future Under Climate Change conference taking place from 7-10 July in Paris, France.
Mapping how malaria might change in response to climate change is even more challenging than mapping climate change itself.
The disease is the result of a single-celled organism belonging to the Plasmodium genus. When mosquitoes bite a person infected with malaria, the disease spreads to the mosquito where it incubates. When the mosquito bites again, a young form of the parasite which ceases the disease is transferred to the human.
Rainy, tropical conditions help mosquitoes breed. But malaria also depends on the presence of humans and a range of socio-economic factors. Poor drainage and water supply, for example, provides standing water for mosquitoes to lay their eggs. Houses open to the environment allow mosquitoes to fly in and infect people. And poor health care increases the number of cases and fatalities.
Professor Morse describes trying to include the full range of factors the drive the spread of malaria as “a complex task”.
“The models require both accurate projections of the seasonally varying mean values of the climatic drivers and their correct variability across a range of time scales from days to multi-decades.”
Adding to the complexity of the task is the fact that malaria outbreaks are poorly recorded even today, making the data for putting into the models patchy to start with.
A World Health Organisation fact sheet from 2012 warns: “At present, malaria surveillance systems detect only around 10 per cent of the estimated global number of cases. In 41 countries around the world, it is not possible to make a reliable assessment of malaria trends due to incompleteness or inconsistency of reporting over time.”
Despite these challenges, Professor Morse has produced some good assessments of how malaria is likely to change in the future. He hopes they can be used to inform government response to the threat of malaria.
And most recently, he has tried out his team’s models on a similar disease, Rift Valley Fever.
“They are both spread by mosquitoes but different types. Both are related to rainy seasons but Rift Valley Fever is more epidemic in nature, appearing in areas every few years, often after heavy rains.”
“Malaria affects humans, whereas Rift Valley Fever is more important as a animal disease… For Rift Valley Fever the major economic impacts for people are losing cattle - their capital - in Africa.”
This is part of a blog series profiling climate scientists, economists, social scientists and civil society members who are presenting and discussing innovative climate science at Our Common Future. For more follow @ClimatParis2015 and #CFCC15 on Twitter.
