Malaria Alerts From Space

In India, for example, where Welch is doing research, health officials are talking about setting up a satellite-based malaria early warning system for the whole country. In coordination with mathematician Jia Li of the University of Alabama at Huntsville and India's Malaria Research Center, Welch is hoping to do a pilot study in Mewat, a predominantly rural area of India south of New Delhi. The area is home to more than 700,000 people living in 491 villages and 5 towns, yet is only about two-thirds the size of Rhode Island.

"We expect to be able to give warnings of high disease risk for a given village or area up to a month in advance," Welch says. "These 'red flags' will let health officials focus their vaccination programs, mosquito spraying, and other disease-fighting efforts in the areas that need them most, perhaps preventing an outbreak before it happens."

Outbreaks are caused by a bewildering variety of factors.

For the mosquito species that carries malaria in Welch's study area, for example, an outbreak hotspot would have pools of stagnant water where adult mosquitoes can deposit their eggs to mature into new adults. These could be lingering puddles on dense, clay-like soil after heavy rains, swamplands located nearby, or even rain-filled buckets habitually left outside by villagers. A malaria hotspot would be warmer than 18°C, because in colder weather, the single-celled "plasmodium" parasite that actually causes malaria operates too slowly to go through its infection cycle before the host mosquito dies. But the weather mustn't be too hot, or the mosquitoes would have to hide in the shade. The humidity must hover in the 55% to 75% range that these mosquitoes require for survival. Preferably there would be cattle or other livestock within the mosquitoes' 1 km flight range, because these pests actually prefer to feed on the blood of animals.

Image courtesy CDC Countries affected by endemic malaria are indicated in yellow.

If all of these conditions coincide, watch out!