Those who live in Evanston and Wilmette are advised to keep pets indoors and windows closed Monday night as crews spray for mosquitoes.
The North Shore Mosquito Abatement District will start spraying around 8 p.m. from Gilson Park on the north to Golf Road on the south until 2 a.m. Tuesday.
As of last week, 27 human cases of the West Nile virus were discovered in Illinois. The state already has surpassed last year's number of human cases, and the number keeps getting worse.
"This summer has been hot and dry, the perfect combination for the Culex mosquito, the species that is known to carry the virus," the Kane County Health Department said in a statement. "It is likely we will see more activity before the season is over."
Kane County announced last week the death of a 64-year-old Elgin man with the virus.
The virus also is to blame for the death of Lombard's long-time village president, 76-year-old Bill Mueller, who battled cancer. Another suburban official, Evergreen Park Mayor James Sexton, also contracted the virus and expects to make a full recovery.