Humans Help to Spread Malaria

Malaria requires two things--a host (a human) and a vector (the mosquito). In areas where malaria is endemic (i.e., a high fraction of people have the parasite in their body), the emphasis has been on controlling mosquitos and exposure to mosquitos. But it has also been known for a long time that malaria-positive humans can spread the disease by going to places where mosquitos exist, being bitten, and then having the mosquito infect someone else who would not otherwise have been at risk. A new study published in Science by a well-know group of malaria researchers shows how this phenomenon can now be tracked and mapped using cell phone data. NPR summarizes the research:

Researchers at Harvard School of Public Health tracked the texts and calls from nearly 15 million cellphones in Kenya for an entire year and then used the data to make a map for how malaria spreads around the Texas-sized country. The results were unexpected.

The roads to and from the capital city, Nairobi, are the most heavily traveled, yet they aren't the most important for spreading the disease throughout the country.
Instead, regional routes around Lake Victoria serve as the major disease corridors for the parasite. And, towns along the routes are hot spots for transmitting malaria to the rest of the country.

 The data also confirm what a few epidemiologists had feared: Malaria seems to be getting into some African megacities, like Nairobi.

Malaria doesn't typically occur in large cities because mosquitoes don't thrive there. "But some studies suggest that mosquitoes are adapting to the city," Douglas Fuller, a geographer at the University of Miami, tells Shots. "This study shows you where Nairobi is getting its malaria."

To curb malaria throughout Kenya, the disease-travel map points out precise areas for concentrating malaria control efforts and suggests places where stopping malaria won't have a big impact.

The idea would be that, because of the heavy penetration of cell phone usage in developing countries, automatic messages could be sent to be people along specific high-risk routes reminding them to take precautions against mosquitos (sprays, bed nets, etc.). Every little bit helps.