Is West Nile virus now
established in the Western Hemisphere?
A. The continued expansion of West Nile virus in the United States
indicates that it is permanently established in the Western Hemisphere.
Is the disease seasonal
in its occurrence?
A. In the temperate zone of the world (i.e., between latitudes 23.5°
and 66.5° north and south), West Nile encephalitis cases occur primarily in
the late summer or early fall. In the southern climates where temperatures
are milder, West Nile virus can be transmitted year round.