A blue jay tested positive for West Nile virus by the McHenry County Department of Health last week.
The bird was found dead on Tuesday, July 28, in Johnsburg. It was unclear exactly what caused the bird’s death, but there are no obvious external injuries, said Patti Nomm, McHenry County director of environmental health.
The department tests batches of mosquitoes weekly from May through October. So far, no positive results were found in any mosquito.
Nomm said it is “not unexpected” to find West Nile in McHenry County. Residents should take precautions to prevent getting infected by limiting outdoor time during early mornings and evenings, ensuring doors and windows have tight-fitting screens and emptying any stagnant water.
There have been fewer than five human cases of West Nile virus in the past five years, said Susan Karras, McHenry County director of public health nursing. Data shows that there were two cases in 2018. So far, there have been zero human cases this year.
The virus cycles through birds and mosquitos, Karras said. Humans are “dead end hosts” and cannot transmit the infection.
“Some infected birds can develop very high levels of the virus in their bloodstream and mosquitoes can become infected by biting these infected birds and passing to other birds,” Karras said in an email to the Northwest Herald.
West Nile virus effects on humans can vary from minor symptoms to becoming life-threatening. Many healthy people will only experience a fever, headache or body aches, according to the McHenry County health department.
In serious cases, the virus can develop encephalitis or meningitis, which can cause death. People at high-risk for severe symptoms are over 60 years old and have serious health conditions, the McHenry County health department said in a news release.
The health department tests about five to seven birds a year for the West Nile virus. Birds cannot transmit the virus to humans.
The health department advises using insect repellent with at least 20% DEET, which is a chemical that makes it difficult for bugs to smell humans. Other ingredients such as lemon eucalyptus and picaridin also can be effective against mosquitos.
Culex mosquitoes, a common type of mosquito found in Illinois, are most likely to carry the virus. They lay eggs in standing water such as clogged gutters, bird baths, abandoned swimming pools and old tires.
Pets can catch West Nile virus from mosquito bites, too, said Maryellen Howell, McHenry County director of veterinary health. She advises talking with a veterinarian about prevention since human insect repellent like bug spray can be poisonous to animals.