It had been thought that the virus was only transmitted through mosquito bites. The infected birds died five to eight days later. Most of the healthy birds, the researchers found, also became ill from the virus and died five to eight days after the first infected bird died. The setting was a very controlled scientific experiment and we're not sure if or how this relates to what is happening in the wild.
Mosquitoes are the primary means of transmission of the virus between birds and to humans.
But this certainly opens up a host of new questions. Chief among the questions, McLean said, is exactly how the virus moves from bird to bird. He said he and other scientists are working on that question now. We know that the virus attacks the crow's entire body and often affects all the major organs. So far we don't know how sensitive other bird species are to the West Nile virus.