The Minnesota Health Department says West Nile virus has been detected in the state for the first time. Officials say two dead crows, one from Hennepin County and one from Mille Lacs County, have tested positive for the virus. West Nile was first discovered in the United States in 1999 after someone died from the virus in New York City. Health officials say people should be cautious about the disease,but not overly concerned.

	State epidemiologist Harry Hull says he's not surprised West Nile virus has shown up in the state. It's already been found in 32 other states, including neighboring states of Wisconsin, Iowa and North Dakota. Listen to his news conference. (MPR Photo/Tom Scheck)

State epidemiologist Harry Hull says he's not surprised West Nile virus has shown up in the state. It's already been found in 32 other states. He says the virus has been steadily moving west and south after it first appeared in New York City in 1999. Hull says reports of cases in surrounding states made him anticipate the first case would surface in Minnesota this year.

Hull says the virus carrying crows were found in Golden Valley and Isle, which sits on the south shore of Lake Mille Lacs.

"This is exactly what we expected. We suspect that the risk will continue through August and early September, until we get our first freeze and the mosquito population dies off," he says.

Hull says West Nile virus is spread by mosquitoes which feed on infected birds. Those infected mosquitoes then infect other animals, mainly other birds, horses and people. The virus can only be spread by mosquitoes. There's no danger of human infection through exposure to other infected animals or birds.

	West Nile virus is spread by mosquitos that feed on infected animals. It was first detected in the U.S. in 1999, in New York City. New York health official Kristine Smith talked to MPR's All Things Considered host Lorna Benson about how it was discovered. Listen to the interview. (Photo by Jeff Hahn/courtesy of U of M Extension)

Hull says less than 1 percent of the population who are infected by a mosquito will develop West Nile encephalitis, which causes swelling of the brain. The Centers for Disease Control in Atlanta says 152 people have been infected with West Nile encephalitis since 1999, leading to 18 deaths.

There's no known treatment, but the virus is most dangerous to people with weak immune systems and the elderly. Hull says people who contract West Nile virus experience flu-like symptoms, headaches, a high fever and convulsions.

"The risk to individuals is low. You're unlikely to contract the virus, and even if you do you're unlikely to get ill," he says.

Hull says he expects more cases of West Nile virus. He says Minnesotans should not be alarmed, but advises people to take precautions to try to avoid mosquito bites. He recommends wearing long-sleeved clothing and mosquito repellant, and avoiding outdoor activities at dusk and dawn.

	Jim Stark with the Metropolitan Mosquito Control District says his agency will increase its testing for the virus in captured mosquitoes. He doesn't believe the district will increase spraying, unless the virus turns up in a larger number of animals or mosquitoes. (MPR Photo/Tom Scheck)

Jim Stark with the Metropolitan Mosquito Control District says his agency will increase its testing for the virus in captured mosquitoes. He doesn't believe the district will increase spraying.

"We've got one bird here in the metro area, so we haven't found a wide range of birds being infected. We haven't found any mosquitoes being infected with West Nile. So the next step would be finding numerous birds and mosquito pools that have the virus in them," says Stark.

Animal health officials say over 100 different birds are known to carry the virus. They say poultry are generally safe, since chickens and turkeys produce natural antibodies if they're infected.

But horses are a different situation. The University of Minnesota's Will Hueston says one-third of the unvaccinated horses who contract West Nile virus die from it. He says many horse owners in the state vaccinated their horses for West Nile encephalitis when it was first reported in 1999. However, he urges all horse owners to have their animals vaccinated with the annual treatment.

"We know now that West Nile has been identified in crows, so the vaccine won't be 100 percent protection at this point. You need to have enough time for the body to develop its immune system to respond to the virus. But that having been said, vaccinating now is better than nothing," says Hueston.

There was a shortage of vaccine earlier this year, but Dr. Kathy Ott, a veterinarian with the Equine Medical Center in Lakeville, says it's now close to full supply. She predicts that a number of horses will be infected with West Nile virus this year.

"I would certainly believe that there's horses in Minnesota that will come down with it. Maybe not so much in the Twin Cities - primarily because the level of education and knowledge, and the value of the horses, has prompted most of the owners in this area to vaccinate their horses this spring," Ott says. "But in some of the outlying areas people aren't as up on their vaccinations, and those are probably the horses - in northern Minnesota, that type of thing - where you'll see more of the cases."

Meanwhile, Hull says the Health Department will increase testing of dead birds to see if the virus is spreading. He says department officials are concerned about the virus, but more worried about other health problems, mainly E. coli poisoning and bioterrorism.

U.S. Geological Survey Surveillance of West Nile virus activity