The North Shore Mosquito Abatement District said the batch was collected on Monday in a trap and tested positive for the virus on Thursday.

Mosquitoes in San Diego's Rolando area tested positive for West Nile virus, prompting county health advisories.

Illinois has confirmed its first human case of West Nile virus this year, health officials say. The person, who lives in southern Illinois, was hospitalized with complications from the mosquito-borne virus.