316 - New Mosquito on the Block: Tracking the Emergence of Aedes Albopictus in Chicago, 2016-2021

Background: Mosquito surveillance in Chicago for Aedes albopictus began in 2016 with the emergence of new disease threats in the U.S. In 2017, CDC estimated that it was unlikely for Ae. albopictus mosquitoes to live and reproduce in Chicago.  We describe how Ae. albopictus have expanded across Chicago since 2016.

Methods: The Chicago Department of Public Health (CDPH) established its vector control program in 2002. From approximately June-September, adult mosquitoes are collected from more than 80 Gravid and BG-Sentinel traps placed throughout the city, identified and counted in a CDPH laboratory weekly. Counts of Ae. albopictus collected from both types of traps were mapped by trap location and year using ArcGIS to visualize the changes in spatial distribution over time.

Results: Prior to 2016, Ae. albopictus were rarely identified in Chicago. In 2016, 4,260 Ae. albopictus mosquitoes were collected from two traps at a private tire dump site in northeast Chicago. After the tires were removed in 2017, less than 200 Ae. albopictus were collected from these same traps but they were found at three additional trap locations. In 2018, 2,012 Ae. albopictus were collected from 10 different traps including seven in west Chicago. Although the total amount of Ae. albopictus found in 2019 decreased to 837, the number of traps with Ae. albopictus doubled to 20 and were more dispersed throughout the city. By 2020 Ae. Albopictus could be found in almost every section of city and in 2021 they were present in 51 traps, representing nearly two-thirds of Chicago traps.

Conclusions:  Local enhanced mosquito surveillance demonstrated that Ae. albopictus are now consistently found further north in the U.S.  Dedicated resources to enhance local surveillance and mitigation efforts are urgently needed to combat the expansion and endemicity of vectors capable of transmitting these emerging public health threats.