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Rift Valley fever: long-distance diagnosis.

Rift Valley fever: Long-distance diagnosis

Satellite data can be used to predictoutbreaks of a viral disease that affects animals and sometimes humans in Africa, researchers say. The disease, Rift Valley fever, is spread by mosquitoes that thrive in flood conditions; the flooding can be detected indirectly by satellites.

While previous work has suggestedthat satellite data could show the spread of other diseases, the present study, led by Kenneth J. Linthicum of the U.S. Army Medical Research Institute at Ft. Detrick in Frederick, Md., is evidently the first disease-spread study to correlate satellite data with ground-based measurements.

Rift Valley fever, often fatal in sheep andcattle, causes fever and sometimes fatal bleeding in humans. While there have not been any recent outbreaks in humans, a 1977 epidemic in Egypt resulted in 18,000 reported illnesses and 598 deaths.

The current study was based on a chainof connections: Weather satellites can measure green vegetation, which in turn represents the amount of rainfall, which is related to the flood conditions that produce the mosquitoes that carry Rift Valley fever virus.

Over two and a half years, Linthicumcollected mosquitoes to measure their prevalence, as well as whether they carried the virus, and measured flooding and vegetation in two sections of Kenya; at the same time, satellites overhead measured light reflected from the area. By comparing the satellite information with the biological data, he and his colleagues found that certain satellite readings accurately represented flood conditions and viral prevalence, they report in the March 27 SCIENCE.

With the knowledge that conditionsfavoring the virus-carrying mosquitoes are present, says Linthicum, local governments could take steps to eradicate the mosquitoes before they reproduce.

The potential for using satellite data topredict disease has been shown in other studies. In one, Eleanor Cross, a medical geographer at the Naval Medical Research Institute in Bethesda, Md., used satellite data to find infestation areas of the snail that carries schistosomiasis. She did this by correlating the amount of vegetation with historical data on the parasite. And researchers at NASA/Goddard Space Flight Center in Greenbelt, Md., are currently using satellites to monitor ecological conditions across Africa; this information, says Compton J. Tucker, who is involved in the project and is one of the coauthors of the Rift Valley fever study, could be useful for establishing more satellite-disease connections.
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Title Annotation:satellite data used to preict outbreaks of viral disease
Author:Silberner, Joanne
Publication:Science News
Date:Mar 28, 1987
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