SPRINGFIELD, IL – The Illinois Department of Public Health today reported increased West Nile virus activity in Madison and St. Clair counties, including a Collinsville horse confirmed as positive for West Nile encephalitis and 20 mosquito batches identified with the virus.

"The potential for human cases of West Nile disease has increased recently, particularly in southwestern Illinois where there is now evidence that infected mosquitoes are feeding on mammals," said Dr. John R. Lumpkin, state public health director. "Physicians, hospital laboratories and hospital infection control practitioners should be alert to an increased risk to humans."

The 3-year-old horse, which was euthanized July 23, was reported positive for West Nile encephalitis late Monday by the National Veterinary Services Laboratory in Ames, Iowa, and today mosquito batches collected in Collinsville (19) and Caseyville (1) tested positive for West Nile virus by the Department's Chicago laboratory.

Dr. Lumpkin, said even though humans in the area are at increased risk for West Nile disease, less than 1 percent of those bitten by an infected mosquito will get severely ill.

A total of 139 crows and blue jays and 36 mosquito batches in 38 Illinois counties have tested positive this year for West Nile virus since surveillance for the mosquito-transmitted virus began May 1. No confirmed human cases of West Nile encephalitis have been reported in Illinois.

A complete listing of the positive birds and mosquito batches identified so far in Illinois, by county, is available on the Department's Web site at www.idph.state.il.us. Go to the West Nile virus page and select "2002" under surveillance.

Dr. Lumpkin reiterated the following precautions should be taken to reduce the risk of mosquito-borne disease:

• Stay indoors at dawn, dusk and early evening. If outside at these times, wear shoes and socks, long pants and a long-sleeved shirt. Loose-fitting, light colored clothing is best.
• Use mosquito repellent containing 25 percent to 35 percent DEET when it is necessary to be outdoors, applied sparingly to exposed skin or clothing, as indicated on the repellent label. Consult a physician before using repellents on young children.
• Check for and repair any tears in residential screens, including porches and patios.
• Eliminate stagnant water in bird baths, ponds, flower pots, wading pools, old tires and any other receptacles in which mosquitoes might breed.

The Culex or house mosquito, which can carry West Nile virus or St. Louis encephalitis, breeds in warm, stagnant water and begins to increase in numbers early in the summer. Recent temperatures have been ideal for the rapid development and activity of the Culex mosquito and, as a result, a jump in the number of positive birds.

Hospitals and infectious disease physicians have been notified of the increase in detection of birds with West Nile virus and reminded to order tests for arbovirus infections for patients with appropriate symptoms.

In 2002, West Nile virus activity has been detected in at least 32 states, including Illinois, and Washington, D.C., in the United States and three Canadian provinces. There have been human cases reported in at least three states this year – Louisiana, Mississippi and Texas.

Most people infected with West Nile virus have no symptoms of illness, but some may become ill, three to 15 days after the bite of an infected mosquito. Infections can be mild and include fever, headache and body aches, or severe and marked by headache, high fever, neck stiffness, stupor, convulsions, muscle weakness, paralysis and, rarely, death. All residents in areas with West Nile virus activity are at risk of getting West Nile encephalitis; those at the highest risk are persons 50 years of age or older.

West Nile virus was first confirmed in Illinois in September 2001 when two dead crows from the Chicago metropolitan area tested positive for the virus.

2002 West Nile virus surveillance information can be found on the Department's Web site at www.idph.state.il.us/envhealth/wnvsurveillance_data_02.htm.