Minnesota Department of Health

News Release

June 30, 2005

Contact information

First bird tests positive for West Nile virus in 2005
Confirmation of disease in crow signals start of mosquito bite prevention season in Minnesota

A dead crow found in Dakota County on June 24 has tested positive for West Nile virus (WNV) at the Minnesota Department of Health (MDH) Public Health Laboratory.

“Confirmation of our first bird means that the virus is starting to circulate between birds and mosquitoes and soon there will be a heightened risk of infection in humans,” said David Neitzel, a mosquito and tick-borne disease specialist with MDH. “If they are not doing so already, people now need to begin taking steps to protect themselves from mosquitoes so they do not become infected.”

There have been no human cases of West Nile yet in Minnesota this year. The highest risk of West Nile infection for people is from mid-July to mid-September, with the peak in August. West Nile is transmitted through the bite of a mosquito that has picked up the virus while feeding on an infected bird. The illness is not spread person-to-person.

To reduce your risk of being bitten:

• While outside among mosquitoes, use a good mosquito repellent, such as those containing no more than 30 percent of the active ingredient DEET. Products containing the active ingredient picaridin are also now commercially available.
• Minimize outdoor activities at dusk or dawn, when mosquitoes are most actively feeding.
• Wear long-sleeve shirts and long pants if you have to spend time in an area where mosquitoes are biting.
• Eliminate mosquito breeding sites on and around your property – including items such as old tires, buckets, clogged rain gutters, cans and other containers and anything else that can hold a small amount of water. Change the water in birdbaths and horse troughs at least weekly.

Most humans infected by the West Nile virus show no symptoms. About 20 percent of infected people will have symptoms such as a fever and headache. Less than one percent become seriously ill. Symptoms typically occur within three to 15 days after the bite of an infected mosquito. The most serious symptoms of West Nile infections include high fever, muscle weakness, stiff neck, disorientation, and convulsions. The highest risk for serious illness and death is among people over 65 years of age.

West Nile virus was first detected in Minnesota in 2002. That year, 48 Minnesotans became ill with West Nile infection. In 2003, 148 human cases were reported with four deaths. In 2004, there were 34 cases with two deaths. West Nile virus has been found in every county in Minnesota, but human disease risk is typically higher in western and central Minnesota counties.

Mosquito surveillance programs were put in place many years ago by state and local public health officials, and expanded when West Nile appeared in the United States in 1999. Those programs involve the trapping and testing of mosquitoes, as well as testing a limited number of dead birds from around the state. Residents who spot crows or blue jays that have died without an obvious cause are asked to use the dead bird reporting form on the MDH Web site or call 612-676-5055.

More information on West Nile and other forms of mosquito-borne encephalitis are available on the MDH Web site, and on the CDC site. People who have general questions about West Nile virus can call MDH at 612-676-5414 (toll free 1-877-676-5414) between 8 a.m. and 4:30 p.m. Monday through Friday.

-MDH-

For more information, contact:

Doug Schultz
MDH Communications
(651) 215-1303

David Neitzel
Vector-borne disease specialist
(612) 676-5414

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