Many factors affect the spread of West Nile: which particular mosquito species are infected, weather conditions, rain--especially conditions that cause areas to flood and then dry up again--and how much pesticide is sprayed. This year, epidemiologists are on alert in all 48 contiguous states, and some believe the virus will spread and become endemic, though not necessarily severe, throughout the United States and the Americas.
"There are no natural barriers to the spread of this virus in the U.S., so it is anticipated it will spread across the United States and down into Central and South America," says Margo Brinton, a professor of biology at Georgia State University. "On the edge of the spread, where new individuals will be infected, there will be a lot of birds ... and mammals [dying], and there will be human cases." The good news is that in regions where the virus has been active, ...
