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Who's
Afraid of This Little Fellow?
By
RICHARD PÉREZ-PEÑA
New
York Times, August 22, 2003
Remember those fears that once loomed so large but now seem like overblown relics? Killer bees . . . flesh-eating bacteria . . . that Y2K thing . . . West Nile virus. All right, fear of West Nile is no misty memory to the people reeling from it in the Plains states. They see more new cases each week than New York has had in four years. Still, in our metropolitan area, where the West Nile form of mosquito-borne encephalitis first made the leap from Old World to New in the summer of 1999, it has come to feel ho-hum — quite a change from the great attention and anxiety it drew back when. So were we overwrought then? Too complacent now? Maybe a little of both? Even the public health officials disagree, or are not sure. At the time of the first outbreaks, "I think it was an appropriate level of concern by the press and the public," said Dr. Annie Fine, medical epidemiologist at the New York City Department of Health and Mental Hygiene. "It was something new, and we didn't know the size of the outbreaks" until much later, Dr. Fine said. And yet, she conceded, "There's been much more attention paid to West Nile, per case, than some other health problems that deserve some attention." An electronic archive search of nine large newspapers in the region turned up 421 references to West Nile this year through Friday. During the same period in 2000, there were 847, and the articles were longer, more urgent in tone, and more prominently displayed. The decline stems partly from the relative mildness of the West Nile outbreak this year in this part of the country, probably because of the weather. With the mosquito season winding down, there have been 34 human cases and 5 deaths so far in New York, New Jersey and Connecticut, including two deaths in New York City last week. The Department of Health and Mental Hygiene announced on Friday that a 69-year-old Queens man and a 93-year-old Brooklyn man were the second and third West Nile fatalities in the city this year. Officials caution, though, that the numbers will rise because the diagnosis often lags weeks behind the disease. Last year, there were 123 cases and 5 deaths. Health experts say it may also be that after 9/11, anthrax attacks, two wars and the SARS epidemic, people find it harder to get worked up about each menace. West Nile virus is in the Americas to stay. The intensity of outbreaks will wax and wane from place to place, with good years and bad. Which means that West Nile could easily make a brutal comeback here next summer, killing hundreds of people in the metropolitan region. But familiarity breeds complacency. Take influenza, an illness that, like West Nile encephalitis, is seasonal, varies each year by region, spreads easily and is most likely to kill the elderly and the weak. People can take easy, concrete steps to avoid both: flu shots and good hygiene in one case, long sleeves and mosquito repellent in the other. Influenza kills more than 30,000 people each year in the United States, compared with fewer than 300 who died from West Nile last year. Yet rarely does a flu outbreak inspire the kind of dread West Nile does. People have so little fear of the flu that barely half of those who should get preventive shots each year actually do. Many other infectious diseases also kill more people than West Nile, including meningitis, hepatitis and AIDS. "The initial fright about West Nile was not about the numbers," said Dickson Despommier, a professor at the Mailman School of Public Health at Columbia, who has written a book about West Nile. "People always react to the new, surprising thing, even if it's terribly remote. Look at how much you hear about things like Lhasa fever and Ebola virus." People naturally assumed that as the West Nile virus became more entrenched, it would spread around the country, and each year would bring more cases than the last. Scientists say that view is at least partly mistaken. Who's Afraid
of This Little Fellow?
(Page 2 of 2) The virus has followed a neat geographic progression. The first years, it was concentrated on the East Coast. Last year, most cases struck to the west, between Appalachia and the Mississippi. This year, the disease hit hard still farther west, in relatively thinly populated states like South Dakota, Nebraska and, hardest of all, Colorado, which has had more than 1,500 diagnosed cases, 27 of them fatal. But researchers say that pattern and the severity of any outbreak probably have as much to do with the weather as with anything else. The mosquito species most responsible for human infection — Culex pipiens in the East, and Culex tarsalis in the West — breed best in brackish, standing water rich in rotting vegetable matter. Their ideal is a marsh, an irrigated field, or a potted plant on a patio. Frequent summer rain, as the Northeast has had this year, means the water is too fresh for the bugs' liking, and their eggs are likely to be washed away. In addition, scientists say, the amount of virus inside the mosquitoes rises sharply as temperatures go up. "So the ideal condition for a human outbreak is a wet spring, followed by a hot, dry summer, when the standing water shrinks and becomes dirtier," said Dr. Lyle R. Petersen, acting director of the division of vector-borne infectious diseases for the federal Centers for Disease Control and Prevention, in Fort Collins, Colo. "That's exactly what we've had in Colorado this year." Professor Despommier said it may also be that many of the birds that are the mosquitoes' favored prey leave dry areas, making the mosquitoes more likely to feed on humans instead. Public health agencies have worked hard to combat West Nile, spraying pesticides and larvacides, and educating the public about the benefits of using mosquito repellent, wearing long-sleeve shirts, staying indoors at dusk, and emptying pools of standing water. But health experts say that while the anti-mosquito efforts are a good idea, it is not clear how effective they are. Dr. Fine said that follow-up tests showed that spraying greatly reduced the number of mosquitoes and their larvae, but that when it came to personal precautions, "many fewer people do that than we would like." Experts also warn that it is early yet in the natural history of West Nile in North America, so it is hard to know what the numbers mean, and it is harder still to make any predictions. There have been more cases than ever diagnosed this year, more than 4,300 nationally and still climbing, but that is due partly to better detection of mild cases. The number of fatal cases is on track to be about the same as last year. Most people who are infected never get sick, yet every infected person becomes immune to the disease for life. Does that mean that a generation from now, a large part of the United States population will be impervious to West Nile? Will the birds that carry it develop immunities, as they have to other forms of encephalitis that they carry? Will bird populations recover from the enormous die-offs caused by West Nile? If not, will that change the shape of human outbreaks? Will the virus itself evolve to become more virulent? No one knows. "One way or another, we should take it seriously," said Dr. Petersen of the C.D.C. "West Nile is probably never going to be one of our leading public health threats. But even if it continues like it is now, and West Nile kills about 300 people a year, that's 300 people, and you can't say that West Nile doesn't matter." Copyright
© 2002 Global Action on Aging |
