As plagues go, those numbers are small. It's not going to kill everybody on the block, but given the fact that the virus has spread over a very large area puts a large percentage of the population at risk of getting infected. 445 mosquito pools. As birds return north next spring, he says, they will fan out toward the Midwest, possibly bringing the West Nile virus into new territory. It could be all over the country in four to five years, he says.
Scientists agree there is much about the virus that is unpredictable.
While it is similar to other viruses, most notably St. Louis encephalitis, there are some baffling differences. St. Louis encephalitis, a disease that has been in the USA since the 1930s, and the West Nile virus are transmitted by mosquitoes. Both cause the same sort of disease in humans. St. Louis encephalitis does not kill birds. That was one of the clues that this was a different virus.