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[RIO DE JANEIRO] Scientists are trying to discover whether the virus that causes West Nile fever, which reached the United States in the 1990s and last year caused 246 deaths there, has reached South America, even though no such cases have yet been reported.

The research team seeking evidence of the virus includes entomologists, ornithologists and virologists from Brazil, Puerto Rico, the United States and Venezuela.

West Nile virus, which is commonly found in Africa, western Asia and the Middle East, is transmitted to humans via a mosquito bite. And migratory birds — which can be infected in the same way — are thought to play a significant role in the disease's expansion across the globe.

"This is the first intensive study on the potential presence of the virus in South America," says Anthony Erico Guimarães, an entomologist from Brazil's Oswaldo Cruz Foundation, and member of a team that has received US$300,000 from the US National Institutes of Health to conduct the research.

"Some species of mosquitoes found with the virus in the south of the United States are common in Latin American urban areas, and the focal points of the disease may therefore occur in such cities."

The study begins in August in Venezuela, whose coast is crossed by many migrating birds on their way to the southern hemisphere from North America. Samples from birds will be tested for the virus at the beginning and end of the migratory period. Mosquito species found in Venezuela that are known to carry the virus in Africa, Europe, the Middle East and Asia will also be tested.

In addition, 2,000 horses will be studied. These play a potentially important role in the cycle of the disease, as they can also be infected and act as a 'reservoir' of the virus.

In parallel to the studies in Venezuela, research will be carried out in the Pantanal wetlands of Mato Grosso, in west central Brazil, another important site for migratory birds that could be carrying the virus from North America.

In humans, the West Nile virus can produce symptoms similar to those of influenza, with fever, headache and skin rash. But complications such as convulsions and paralysis can also result. More severe effects, including encephalitis and meningitis, occur in less than one per cent of infected patients and can lead to death.

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