The presence of West Nile virus in Minnesota and other states should not cause the people to panic. The risk of human infection is low in Minnesota, says entomologist Jeff Hahn of the University of Minnesota Extension Service. And common sense strategies to minimize exposure to mosquitoes can reduce the risk even more, he adds.
"The only known way to become infected with West Nile virus is to be bitten by a mosquito that's carrying the disease," says Hahn. "Minnesota is home to about 50 different types of mosquitoes. However, the two most common species, the vexans mosquito and the cattail mosquito, have not proven to be effective transmitters of West Nile virus."
Hahn says there are several species of "Culex" mosquitoes in Minnesota that are more efficient transmitters of the disease. Fortunately, these are much less abundant in Minnesota, reducing the chances of an encounter with a West Nile virus-infested mosquito.
While the risk of West Nile virus for humans is generally low, Hahn recommends common sense steps to minimize mosquito bites. "Avoid being outside at dawn, dusk and in the early evening when mosquitoes are most active," he says. "Wear protective clothing, including long-sleeved shirts and long pants, when you are in areas where mosquito numbers are high."
He also recommends using repellents. "The most effective product is DEET," he says. "Apply DEET to clothes or skin, but only enough to lightly cover the desired areas. Do not over apply repellents."
Hahn recommends cutting areas with weeds and tall grass near your home, because these areas harbor mosquitoes. Leave yard lights off when possible to avoid attracting the insects unnecessarily. You can also try sodium lights, which are less attractive to mosquitoes than fluorescent or incandescent lights. Make sure window and door screens fit properly and repair or replace any screens with holes or tears.
It's also important to remove any containers that may hold water, such as old tires. If you can't remove them, then drain them. If this isn't possible, Hahn suggests applying a small amount of vegetable oil to the water's surface. This will suffocate any larvae in the water. Keep gutters cleaned so water doesn't accumulate.
"Be skeptical of traps, electrocutors, sound-repelling devices and other products that offer mosquito control," says Hahn. "If a product's claims seem to good to be true, they probably are."
Hahn says most people infected with West Nile virus either show no symptoms or experience mild illness before recovering. Those getting the mild illness may have fever, headache and body aches. "The disease at its most serious can cause permanent neurological damage and can be fatal," he says. "Fatal cases are more prevalent in people age 50 or older. Fortunately, there have been few serious West Nile virus cases in the United States to date."
West Nile virus was found in Minnesota in July with the discovery of two infected crows, one each in Hennepin and Crow Wing counties. As of Aug. 19, the Minnesota Department of Health had reported a total of 128 birds and 93 horses that tested positive for West Nile virus in 53 counties. Nationally, the Centers for Disease Control and Prevention recorded confirmed infections in 39 states and the District of Columbia as of Aug. 21. The first West Nile virus case was found in New York in 1999.
Further information about West Nile virus is available on the Internet at: http://www.ncpmc.org/NewsAlerts/westnilevirus.html.