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8.11.2000 00:15
W. Nile makes inroads in N. America
 Officials say the virus is here to stay.
The Washington Post
The West Nile virus, a microbe normally found in Africa and Asia that surfaced last summer in New York City, has markedly expanded its range, and appears to be in North America for good, a federal disease surveillance official said yesterday.
Birds or mosquitoes carrying the virus have been found in northwest New York, near Niagara Falls, along the Canadian border north of Lake Placid, and into Connecticut and Massachusetts. It has also been found in New Jersey, though not as widely as it was last year.
Only a single case of human illness caused by the microbe has been found this summer. But that's likely to change, as August is the peak season for transmission of West Nile and other mosquito-borne viruses.
"If there is any time where it's most important for people to follow prevention messages, it's over the coming weeks, into September," said Stephen Ostroff, an epidemiologist and coordinator of West Nile virus surveillance at the federal Centers for Disease Control and Prevention in Atlanta.
The agency reported that 188 dead birds infected with West Nile virus have been found this summer in 34 counties in four Northeastern states. Nearly 60 percent were reported since Aug. 1 alone, evidence of both increased transmission of the virus and a more diligent search for it.
The virus infects many bird species but causes illness in only a few. It appears to be uniformly fatal in crows, which were three-quarters of the infected birds in this summer's tests. Many mammal populations can also become infected, but humans and horses are the only ones that appear to become ill.
This is the most likely time for West Nile virus infections because mosquito populations -- and with them, the pool of infected birds -- have been increasing all summer. After last year's outbreak, researchers tested birds in Queens, a New York City borough, where most of the human cases occurred. About half had bloodstream evidence of previous infection with the virus.
Most West Nile virus infections cause few or no symptoms. Only about one in 300 people become seriously ill, and only a small minority of them die. (Of the 62 cases last summer, seven were fatal.) Common symptoms are fever, severe headache, eye pain, drowsiness, extreme muscle weakness and enlarged lymph nodes. The most serious complication is encephalitis, an inflammation of the brain.
There's no evidence the virus was in North America in 1998. After last year's outbreak, and with evidence that the virus was carried through the winter, "there was little doubt that it's here to stay," Ostroff said.
The report of the bird survey is in the current edition of Morbidity and Mortality Weekly Report, a newsletter published by the CDC.
Find out more about the West Nile virus
, from recent local news to information about the disease to official tracking reports, at:
http://projo.com/specials/westnile/
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