Connecticut’s Mosquito Management Program has launched its annual mosquito monitoring effort to detect West Nile virus (WNV) and eastern equine encephalitis (EEE) across the state. The program, coordinated by the Connecticut Agricultural Experiment Station (CAES), begins June 2 and runs through the end of October. It involves mosquito trapping and testing at 108 sites in 88 municipalities.

In 2024, WNV was found in 309 mosquito samples from 44 towns, primarily in Fairfield, Hartford, and New Haven counties. Thirteen human cases of WNV illness were reported, with onset dates between July 30 and September 15. WNV is the most common mosquito-borne illness in the Northeast since its arrival in 1999.

EEE virus was detected in 72 mosquito samples from 16 towns, mostly in eastern Connecticut. Though there were no human cases in Connecticut last year, the virus caused illness in animals and was reported in neighboring states. EEE remains a rare but serious threat, with occasional deadly outbreaks like the one in 2019.

"The mosquito season has begun," said Dr. Philip Armstrong, Chief Scientist at CAES. “We will be trapping and testing mosquitoes from 108 locations throughout Connecticut to monitor the risk of mosquito-borne disease. Typically, West Nile virus activity peaks from July-September with highest levels of activity in urban and suburban communities in the state. Seasonal transmission of EEE virus, in contrast, occurs more sporadically with focal areas located in rural areas of eastern Connecticut. We encourage everyone to take precautionary measures against mosquito bites, such as covering bare skin and wearing mosquito repellent, especially during dusk and dawn when mosquitoes are most active."

Residents are advised to use EPA-approved repellents, wear protective clothing, and ensure screens are in good repair. For more safety tips and testing updates, visit the Connecticut Mosquito Management Program website at https://portal.ct.gov/mosquito