Last August, as the West Nile virus went on a 44-state, 284-person killing spree, Vicki Kramer found herself troubled by a single case. In California, where Kramer is the state's point person on mosquito-borne disease, the virus hadn't shown up in surveillance of birds or insects. But out of nowhere, a sick 31-year-old woman who hadn't left the Los Angeles area in months had fallen ill. The case was a mystery in many ways, but Kramer figured there were ways to solve it--the deadly disease might have been circulating all along, spread by some other means. Only one question really bothered her: why hadn't she seen it coming?
She will this year--and it's surely coming, and fast. Despite last year's outbreak, few people have developed immunity to the disease, says Dawn Wesson, an associate professor of tropical medicine at Tulane University. Neither have the 138 species of birds and numerous other types of wildlife West Nile has now infected. And while geography may have kept a few regions in the clear last year, no state will be safe in 2003. The heavy rains quenching the drought-starved Midwest and deluging the Northeast are leaving pools of standing water, ideal nurseries for mosquitoes. The Southwest, too, is in trouble. If West Nile brings down its populations of predatory birds, which usually keep rodent populations low, the rat-borne plague and hantaviruses could spread unchecked there in what Mary Pearl, president of the Wildlife Trust, calls a "triple whammy." Even Alaska is worried--cold has proved to be no barrier for the disease, which has moved into Canada, and migrating birds may carry it north after making pit stops in infected areas. Hawaii isn't safe, either, though the "bird" that could bring West Nile to the islands is actually an airplane, ferrying mosquitoes along with honeymooners. (The mosquito that infected the California woman may have hitchhiked the same way.)
With the deck stacked so perilously against them, states are doing their best to prepare. Louisiana has stepped up its surveillance of dead birds, and California has increased the number of "sentinel chickens" it bleeds every two weeks looking for the virus. The Centers for Disease Control is partnering with zoos to make sure none of their animals become unwitting sentinels themselves. And almost all states are employing weapons of mass mosquito destruction, wiping out larvae with hormones that stop their growth in mid-adolescence and bacteria that dissolve the insects' guts. Local health departments are helping, too; many have hot lines, and some are supplying homes with mosquitofish, guppylike animals that feast on the insects in backyard ponds. All are encouraging people to get rid of standing water. But public-awareness campaigns are only as good as the people who pay attention to them; a neighborhood that combats West Nile halfheartedly is no more effective than a mosquito net rent with holes. So Kramer is gearing up for the worst. "In 2001, we received 68 calls on our state dead-bird hot line," she says. "Last year there were 3,600." And this year? "You never know what to expect." Compared with last August, though, she's got a good guess.