Joliet Mosquitoes Tests Positive For West Nile Virus

Ruzanna Harutyunyan's picture

Mosquito samples collected August 14 represent the Will County Health Department’s first confirmed West Nile Virus (WNV) activity for 2009.

The mosquito samples were taken from a Will County Health Department monitoring site located not far from the Health Department’s main office complex in southeast Joliet. The Health Department operates seven monitoring sites across the county, and collects samples for analysis from each site twice weekly. Samples from two separate mosquito batches tested positive for WNV. Positives were confirmed August 17 and 18, using the Rapid Analyte Measurement Platform (RAMP).

Will County is one of at least 17 Illinois jurisdictions to report WNV activity during 2009. Earlier this month, a monitoring site in Northern Will County operated by the Illinois Department of Public Health reported the area’s first mosquito positive of the summer.

No human cases have been reported in Illinois to date, but the state has reported at least 62 positive mosquito batches. The list of counties reporting WNV activity so far this year includes: Cook, Kane, DuPage, Kendall and Grundy counties.

WNV is a potentially serious infection transmitted to humans through the bite of an infected mosquito. The virus has accounted for more than 28,500 laboratory-confirmed human infections and more than 1,065 U.S. fatalities since 1999. There have been 52 laboratory-confirmed human cases and two Will County fatalities reported since 2002.


Illinois monitoring sites similar to those operated by the Will County Health Department totaled 658 WNVpositive mosquito samples in 2008. There were 8 virus-positive mosquito samples collected in Will County a year ago, including five from monitoring sites operated by the Will County Environmental Health. Three of the 2008 virus-positive samples taken from Will County Environmental Health sites were collected from Bolingbrook. Sites in Homer Glen and Frankfort also yielded a virus-positive sample.

“We experienced an extraordinarily cool July and that may have retarded WNV activity,” according to Elizabeth Bilotta, Will County Environmental Health director. “However, warmer weather has returned, and that may accelerate the pace of WNV activity. We know the virus is still with us and personal protection measures are still warranted.”

Mild cases of WNV (typically referred to as West Nile Virus fever), may cause a low-grade fever or headache. More severe infections are marked by the rapid onset of high fever with head and body aches, disorientation, tremors, convulsions and, in the most severe cases, paralysis or death. Symptoms, if present at all, usually occur from 3-14 days after the bite of an infected mosquito.

Persons at the highest risk for serious WNV illness are those 50 years of age or older. The average age of 2008 Illinois human cases was 54 years.

The Health Department also collects a limited number of perching birds for WNV laboratory analysis. To report dead birds, telephone 815-740-7631 any time.

The best way to prevent WNV and other mosquito-borne illnesses is to reduce the number of mosquitoes around your home and neighborhood. Eliminate any standing water from your property, keep vegetation cut short, and repair torn window screens that could enable mosquitoes to enter your residence.