The state bought enough pesticide to drop into tens of thousands of catch basins. N.Y. And there are signs it may be moving north. Although there have been no further human infections, Connecticut scientists found the virus in mosquitoes in the southern part of the state last fall and in more than 1,000 dead crows. For reasons even scientists don't fully understand, crows are highly vulnerable to the West Nile virus. Birds are key to the spread of the virus.
Scientists say infected mosquitoes bite wild birds, such as crows, robins and starlings.
The birds can migrate great distances, thus spreading the virus. Another mosquito can bite the infected bird, then bite a human. Coastal states from Massachusetts to the Gulf of Mexico are the most vulnerable for a West Nile outbreak because of the birds' migratory patterns, according to scientists. In Massachusetts, officials say no sign of the virus has been found in birds, bugs, animals or humans. For that reason, the head of the state's mosquito surveillance program said Massachusetts will take a more measured approach.