The warning itself was possible because of a model of how disease spreads that Dr Linthicum helped design. And the data that were plugged into that model came from satellites.
What the researchers at Goddard had noticed at the time of the first outbreak was that in the months preceding it, surface temperatures in the equatorial part of the Indian Ocean had risen by half a degree. These higher temperatures brought heavy and sustained rains, cloud cover and warmer air to much of the Horn of Africa. Mosquitoes multiplied wildly—and lived long enough for the virus that causes the fever to develop to the point where it is easily transmissible. In September 2007 the researchers saw the same thing happening in the ocean, and suspected the same consequences would follow.
Attempts to foresee epidemics such as these have traditionally relied on fieldwork on the ground. This is often slow and expensive. Crunching data from satellites is much less costly. Satellites transmit copious information on temperatures, precipitation, vegetation cover and even the health, moisture content and chlorophyll-production of plants.
