CHICAGO (CBS) — Testing for West Nile Virus is starting two weeks earlier than normal this year, following the unseasonably warm winter and spring.

As WBBM Newsradio’s John Cody reports, the Illinois Department of Public Health will run the $70 West Nile tests on dead cows and horses turned in by local animal control department. But the main target is perching birds.

LISTEN: WBBM Newsradio’s John Cody reports

“That would be the cardinals and grackles, but particularly birds such as crows and blue jays because they are very susceptible to West Nile virus,” said Dr. Linn Haramis, a Public Health Department entomologist.

Haramis says tests showed West Nile virus in half of all the dead birds collected during last year’s warm summer.

Twenty percent of those who are bitten by mosquitoes with West Nile contract the disease and 5 percent get severely sick.

Symptoms can include fever, headache and body aches. People over the age of 50 and those with chronic diseases such as heart disease or cancer may be more at-risk for meningitis or encephalitis, two life-threatening diseases, but people of any age can contract the disease.

Last year West Nile sickened 34 and killed three people in Illinois.

Watch & Listen LIVE