In December, 1997, goats, cattle and sheep began dropping dead in north-eastern Kenya. A month later people began doing the same. The cause was Rift Valley fever. Nearly 100,000 animals died and as many humans were infected. Hundreds of people died.
Exactly ten years later, livestock once again began dying off in the same area, but the outbreak was largely avoided in humans because NASA scientists had tipped off the Kenyans before things got nasty.
Acting on the news, Kenyan officials distributed mosquito nets and told folks to stop eating their livestock. The 2007 outbreak killed 300 people, but the number would have been twice that or more without the head’s up.
The warning resulted from the research of Kenneth Linthicum, of the US Department of Agriculture, who used data derived from satellites to predict the outbreak.
Linthicum and his colleagues noticed in retrospect that the first outbreak was preceded by a rise of one degree Fahrenheit in the surface temperatures of the Indian Ocean near the east coast of Africa.
That had triggered monsoon rains and cloudy, warm weather over the Horn of Africa, which caused explosive growth in the mosquito population. Linthicum’s team saw the same thing happening in September, 2007.
Heretofore, efforts to predict epidemics relied on slow, expensive fieldwork. Satellite data is cheaper to obtain. It includes information about precipitation, temperature, vegetation cover and chlorophyll production.
Confirming the value of satellite-derived information, Jacques-André Ndione of Dakar’s Centre de Suivi Ecologique cites a satellite study showing that malaria spreads more quickly in suburbs than in cities.
In that study, satellite images revealed that suburbs have more ponds and puddles, and that their longevity, salinity and mud content tended to favor mosquito happy times.
Incidentally, the EDEN project, a public-health cooperative involving European and African countries, has used satellite findings to conclude that malaria, dengue fever and Rift Valley fever will soon enter Europe.
Indeed, chikungunya, a mosquito-borne viral disease previously found only in tropical Africa and Asia, has recently shown up in Italy and Albania. A sign of things to come, maybe?