Located in the Midwestern United States, Illinois is considered to be at low risk of widespread, year-long transmission of Zika virus. The Aedes aegypti mosquito, which is the primary vector for Zika virus transmission, is rarely found in Illinois. The primary risks to Illinois residents for becoming infected with Zika Virus are (1) from travel to and from areas with active Zika virus transmission or (2) individuals who have unprotected sex after one or both sexual partners has traveled to an area with active Zika virus transmission and have been infected.
The Aedes albopictus mosquito is believed to be a secondary [less efficient] vector of Zika virus. Aedes albopictus has been reported from 37 Illinois counties, mostly in the southern two-thirds of the state. This is a “container-breeding” mosquito that uses water-filled buckets, old tires, and similar containers for larval production; it does not breed in ditches, marshes, or other water impoundments in the ground. Additional survey work is needed to determine the presence and public health importance of Aedes albopictus in Illinois.
At this time, local transmission of Zika virus , and is ongoing in U.S. territories and affiliated Pacific Island countries.
Currently, the only Zika virus cases in Illinois are travel associated. Transmission can occur sexually or congenitally. Although very unlikely, infected people who come to or return to Illinois from affected areas could infect mosquitoes if they are bitten while the virus is still circulating in their blood (viremic). However, because the Aedes aegypti is rarely present in Illinois, it is unlikely that locally sustained transmission would occur.