Clues from the Nile
a recent study on the West Nile virus disease throws fresh light on its rapid spread in the us, where it was introduced in 1999. The disease has affected an estimated 215,000 people of whom 770 have died.
The infection causes headache, fever and may also result in encephalitis. The virus is transmitted by Culex pipiens mosquitoes that mostly feed on American robin (Turdus migratorius).
For the study, researchers from the Consortium for Conservation Medicine, New York, New York State Department of Health, New York and Smithsonian Environmental Research Center, Maryland collected C pipiens and caught robins from six affected sites. They then sequenced the dna of blood found in mosquito's stomach.
They found that from May to June, the bird accounted for more than half of mosquito's meals. But when the robins left their breeding grounds, the probability of humans being targeted increased sevenfold. The study appeared in the April issue of the online journal PloS Biology (Vol 4, No 4).
The study may help understand and predict the spread of other diseases such as sars, Nipah virus and avian influenza, where a similar species jump is feared.