West Nile virus spreading faster than expected, officials admit

WASHINGTON -- West Nile virus is sickening people far earlier this summer than usual, and is spreading so quickly -- it's hit 34 states, as far west as South Dakota -- that health officials believe it will reach California this year or next.

Nobody knows how bad the mosquito-borne illness will get -- although a rapidly growing outbreak among 32 people in Louisiana began a month earlier than West Nile has ever struck in this country, a big worry. But it's clear the virus first detected in New York City a mere three years ago has become a permanent summertime threat in most states.

Yet it's fairly easy to prevent: Spray on DEET-containing mosquito repellent when you go outdoors, and don't let puddles collect in flower pots, wading pools or other spots where mosquitoes can breed. One specialist equates the safety steps to the routine of buckling a seat belt before driving.

"That's the level of worry people should have," says Dr. Lyle Petersen of the Centers for Disease Control and Prevention. "You should be concerned enough about it to do something but not have it change your whole lifestyle."

West Nile virus has struck other countries for decades, from the tip of Africa up to Europe and throughout Asia, so its move here probably was inevitable. The CDC has confirmed 161 U.S. cases, including 18 deaths, since the first Americans were diagnosed in 1999.

Officials are investigating if West Nile just killed two people in Louisiana. In addition to 32 West Nile-caused encephalitis cases there, a Mississippian is sick and health officials are investigating 10 similarly ill Texans.

The virus doesn't discriminate: A dead crow was even found on the White House lawn.

West Nile can cause a potentially fatal brain inflammation. Anyone suffering such symptoms as a high fever, severe headache, confusion or difficulty thinking, stiff neck or severe muscle weakness should see a doctor right away. It has struck Americans as young as 16, but those most at risk are over 50.

For every case of West Nile encephalitis, 150 more people are thought to be mildly infected -- not sick enough to see a doctor. They get a flu-like illness, with fever, headache and muscle pains, that lasts two or three days.

How does West Nile spread? It infects numerous types of wild birds, from house sparrows to crows. Mosquitoes spread it among birds, and then to people. A spate of dead birds can be an early warning signal that the virus is circulating in a certain spot.

Aside from people, the mammals most vulnerable are horses. There is a horse vaccine but not a human one, nor is there any anti-viral treatment -- victims get supportive care.

People can't get West Nile from each other or by touching an infected animal. Zoos with exotic birds are not considered particularly risky -- wild birds spread West Nile, and exotic birds that get it usually die quickly.

But even as West Nile races across the country, there's no real predicting how big a threat it will pose each year. Abroad, West Nile hides for years between periodic epidemics -- a pattern likely here, too, says Petersen.

------

EDITOR'S NOTE -- Lauran Neergaard covers health and medicine for The Associated Press in Washington.