Mosquito batches recently collected in northwest suburban Nunda Township and Lake in the Hills have tested positive for West Nile virus.
These batches were collected on July 31 and August 6, and are the first to test positive for the virus in McHenry County in 2015, said officials in a statement.
McHenry County Department of Health officials tested 311 mosquito batches as of August 18, but all other batches have tested negative for West Nile virus, the statement said.
The department will continue to collect and test mosquito batches until mid-October, but the risk of West Nile virus remains until the first frost, the statement said.
Health officials say those infected by the virus experience fever, headache and body aches, but serious illnesses, like meningitis and death, are possible. People over 50 have the highest risk of severe disease, the statement said.
Residents should use insect repellent, wear long sleeved shirts and pants for more protection, and empty any standing water outside, officials said.