The West Nile keeps popping up in more U.S. states. The past month, health authorities in Maine, Illinois, Wisconsin, Iowa, Kentucky, Alabama, and Tennessee reported the agent in birds or other animals for the first time.
West Nile, which had never been found in the Americas until it hit New York City in 1999, has now been detected in 24 states and the District of Columbia, and "we need to assume that it's going to spread throughout the country," says Duane Gubler, head of the Centers for Disease Control and Prevention's arthropod-borne virus lab in Fort Collins, Colorado. Gubler suspects migratory birds transported the virus to southern states such as Florida and Louisiana in the fall of 1999 or 2000; from there, it probably hitched a ride with other birds to the northern Midwest this spring.
So far, the human toll has been relatively low: Early this week, there were 26 diagnosed or suspected cases, including one fatality, compared to 62 cases in 1999 and 18 last year. The virus is a threat primarily to the elderly and people with suppressed immune systems. Even if it conquers the rest of the country, good surveillance, prevention, and control measures should prevent the virus from becoming a major public health threat, Gubler says. "This is a virus we can deal with."