It is not uncommon for West Nile to be detected in local mosquito pools. Last year, Louisiana recorded 617 positive mosquito pools, including four in New Orleans, and three people died of the virus last year, according to the Louisiana Department of Public Health.

West nile virus is a family of enveloped positive-strand, RNA viruses which mainly infect mammals and birds. The virus is usually transmitted through mosquitoes

The Chicago Department of Public Health announced on Friday that the first batch of mosquitoes that tested positive for the West Nile virus were found in the city. This comes after other batches tested positive for the virus in Glenview and in McHenry and DuPage counties.