(STMW) — A batch of mosquitoes collected in southwest suburban Plainfield has tested positive for West Nile virus.

The batch of mosquitoes was collected by Will County Environmental Health employees between Monday and Wednesday, according to a statement from the Will County Health Department. Testing confirmed the presence of West Nile virus on Thursday.

Will County is one of 23 Illinois counties to report West Nile virus activity as of Wednesday, the health department said.

The Illinois Department of Public Health reported 1,271 positive mosquito tests statewide last year, along with 41 West Nile-positive birds, 44 human cases and four deaths. No human cases were reported in Will County last year.

West Nile virus is transmitted through the bite of a mosquito that has picked up the virus by feeding on an infected bird. Common symptoms include fever, nausea, headache and muscle aches, according to the IDPH.

Most people infected will not show any symptoms, but in rare cases patients can be come severely ill or die. Those over 50 and people with compromised immune systems are at higher risk for severe illness.

To avoid West Nile, residents should limit time outside between dusk and dawn, when mosquitoes are most active. Eliminate sources of standing water, and wear long sleeves, pants and mosquito repellent when outside, health officials recommend.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2015. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)