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7.27.2001 00:05
West Nile here to stay,
but losing some sting
• While the virus is firmly established in the eastern U.S. researchers are working to find a vaccine, and many who contract the virus have mild symptoms or none at all.
BY PETER LORD
Journal Environment Writer
West Nile virus killed a horse in the Florida panhandle recently, marking both the farthest south the disease has struck since it first emerged in New York City two years ago, and the earliest in the summer that the deadly form of encephalitis has stricken a horse.
Recent studies also show, however, that in areas where a horse has been stricken, many other horses, as many as 23 percent, have tested positive for West Nile and shown no signs of illness.
What's more, licensing of the first vaccines that protect horses is pending, according to Dr. Thomas Gomez, a veterinary epidemiologist with the U.S. Department of Agriculture.
Those kinds of bad-news, good-news developments on the West Nile phenomenon were peppered throughout an unusual news conference from Atlanta yesterday.
Reporters from throughout the East Coast were briefed in a conference call from Atlanta by Gomez, Dr. Kathryn Converse, a wildlife disease specialist with the U.S. Geological Survey's National Wildlife Center in Madison, Wis.; and Dr. Stephen Ostroff, a medical epidemiologist from the U.S. Centers for Disease Control and Prevention.
Ostroff said that every case of West Nile to emerge since the New York outbreak has been a clone of the original virus that arrived here in the summer of 1999.
"All the viruses since then have been essentially identical," Ostroff said. "We haven't seen any mutated viruses that could increase or decrease in their virulence."
Ostroff said it's clear that West Nile, a disease common in Africa and the Mideast, will now be a permanent fixture in the United States. But he also said that based on what he's seen since the New York outbreak, people learn to deal with it.
"I can say quite honestly that in the Northeast, now that the public has sort of lived with West Nile for the last couple of years, they have by and large adapted to the fact that it's there," he said. "We anticipate it's going to be there forever."
So far in Rhode Island this year, state surveillance efforts have found three crows killed by West Nile. The crows were found in Charlestown, Warwick and Coventry.
State officials were a little surprised to see dead birds so early -- they first turned up in May -- but so far there hasn't been any sign of the disease in mosquitoes, which are the carriers of the virus.
New studies show West Nile is 100 percent fatal for crows, according to Converse. Studies also show that crows in captivity can spread West Nile to other crows without having mosquitoes transmit the disease.
She said work is progressing on a vaccine for endangered whooping cranes that have been raised in captivity and are about to be released in the wild.
When West Nile first struck in New York in the summer of 1999, 69 people were stricken and 7, all elderly, died. Also 13 horses were killed.
Since then, experts expected to see the disease spread by birds and mosquitoes to different parts of the country, Ostroff said.
"In 2000 we saw the virus move north in the spring, with activity throughout New England," Ostroff said. "In the fall migration, it moved south to Maryland and Pennsylvania."
This year, he said, it moved to Georgia and Florida, and scientists suspect it's in the Carolinas but hasn't been found yet.
Ostroff said the impact on the public has been minimized by good "collaborative efforts between the public and public agencies."
In particular, he cited the public's help in turning in dead birds to state wildlife agencies so they can be tested for West Nile. In addition, he stressed the importance of personal protection. People should use repellents and wear long sleeves when mosquitoes are out and they should look to drain potential breeding spots around their homes.
Efforts are under way to find vaccines and anti-viral drugs, Ostroff said. So far they have not been effective.
But the good news, he said, is that for every severe case of the illness, doctors have found large numbers of less-severe cases, or individuals who have the virus and no indication of illness at all.
It's possible the disease could spread through the United States, Ostroff said. But the types of birds and mosquitoes common in the West are very different, so that might slow the spread westward.
People should avoid getting bitten by mosquitoes, he said. And those who are bitten should be aware there's little chance any single bite will lead to illness.
A reporter from Baltimore asked how big a public health threat is West Nile?
"I guess I can personalize it a bit now that it's been found in Atlanta," Ostroff said. "I'm concerned, but I'm not frightened. It empowers me with information to make important public health decisions.
"If I lived in Baltimore, Maryland, I would use insect repellent and I'd look to see where mosquitoes breed around my house. Would I stay indoors for the rest of the summer? No."
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