June 17, 2003

URBANA--The West Nile virus will soon become more active in Illinois. Although only two infected birds have been found so far this year, it is time to start taking precautions to protecting yourself from this virus that killed 64 people in Illinois in 2002, said a University of Illinois entomologist.

The virus is transmitted through mosquito bites to humans, birds, horses, and other mammals. Philip L. Nixon, Extension entomologist in the Department of Natural Resources and Environmental Sciences at the U of I said that although a variety of mosquitoes can carry the virus, the northern house mosquito is the most likely vector. “A female mosquito picks up West Nile virus particles while feeding on an infected bird. Then, the virus is transmitted into the blood of another bird, human, horse or other mammal the next time the mosquito feeds.”

Nixon said that most people who become infected will show no symptoms, but some may become ill three to fifteen days after being bitten. Typical symptoms are a fever and headache. “In some, particularly elderly people,” Nixon said, “West Nile virus can cause serious disease, including muscle weakness, inflammation of the brain (encephalitis), stiff neck, stupor, disorientation, tremors, convulsions, paralysis, coma, or death.”

A vaccination against West Nile virus is available for horses. Dogs, cats, and other mammals can also get West Nile virus, but as with humans and horses, most will make a full recovery.

Some precautions can be taken to avoid being infected by the virus according to Nixon. “This mosquito is primarily a dawn and evening biter, so restrict your outdoor activities at those times. Wear a hat, long-sleeved shirt, long pants, shoes, and socks to reduce the amount of exposed skin. If you are outdoors when mosquitoes are biting, apply an insect repellent containing DEET,” said Nixon. “Although fine for skin application, DEET should not be ingested. For young children who are unable to understand that they shouldn't lick the material off of their hands or arms, use another product such as repellents advertised for child use or other repellents that don't contain DEET. Although these are less effective, they should be less toxic if ingested.”

Emptying the water from outside containers can help keep the mosquito population down. Nixon said, “The northern house mosquito breeds in containers of standing water. It lays several black eggs in a mass about one-eighth inch across that floats on the water surface. The water typically has a large amount of decaying organic matter in it, giving the water a dark color and putrid smell. So, by keeping gutters clean of fallen leaves, removing old tires and other water-collecting debris, stocking water lily ponds with goldfish or minnows, and emptying and cleaning wading pools, birdbaths, and pet water bowls weekly, you can greatly reduce the number of these mosquitoes in your yard.”

The northern house mosquito is a small, medium brown, quiet biter that is most common in Illinois from mid-June through the rest of the summer and fall. “A quiet biter means that it lands softly on the skin and the bite is painless enough in many people that they do not notice it,” Nixon said, “It may not buzz around your ear and if it does, the hum of its wings is not very loud.”

Information on mosquito control is available on the University of Illinois Extension website at: http://www.ipm.uiuc.edu/wnv/index.html

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