Press Releases

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Risk of Mosquito-Borne Diseases Continues

Eastern Equine Encephalitis Positive Mosquitoes Found in 6 Connecticut Towns

West Nile Virus Detected in 33 Connecticut Towns


Dr. Philip Armstrong
Phone: 203-974-8510; Email:

Dr. Jason White
Phone: 203-974-8440; Email:

The Connecticut Agricultural Experiment Station
123 Huntington St.
New Haven, CT 06511

New Haven, CT – The State Mosquito Management Program is warning Connecticut residents about the risk of infection by eastern equine encephalitis (EEE) and West Nile virus (WNV) this season. So far, the Connecticut Agricultural Experiment Station (CAES) has detected EEE-infected mosquitoes in: Hampton, Killingly, Thompson, Tolland, Voluntown, and Woodstock. In addition, WNV-infected mosquitoes have been detected in: Bethel, Branford, Bridgeport, Colchester, Danbury, Darien, East Haddam, East Haven, Fairfield, Glastonbury, Greenwich, Hartford, Hebron, Killingworth, Manchester, Mansfield, Middlefield, Milford, New Canaan, New Haven, North Stonington, Norwalk, South Windsor, Stamford, Tolland, Wallingford, Waterbury, Waterford, West Haven, Westport, Wethersfield, Willington, and Wilton. Two human cases of WNV infection have also been reported in Connecticut so far this year.

"We are seeing a late season rise in the numbers of mosquitoes carrying EEE virus in communities in eastern Connecticut,” said Dr. Philip Armstrong, Medical Entomologist at the CAES. “In addition, we are continuing to detect West Nile virus in numerous towns throughout the state. Late summer-early fall is the critical time of the year when virus activity reaches its peak in the mosquito population and the risk is expected to continue until the first hard frost in October."

“We are experiencing a very active mosquito season for this time of year due to the unseasonably warm weather during recent weeks,” said Dr. Jason White, Director of CAES. “We strongly encourage residents throughout the state to take simple steps to prevent mosquito bites. This includes applying insect repellent and covering bare skin, especially during dusk and dawn when biting mosquitoes are most active.”

Map of Connecticut showing activity of eastern equine encephalitis in 2023.

Map of Connecticut showing activity of West Nile virus in 2023.

To reduce the risk of being bitten by mosquitoes, residents should:

  • Minimize time spent outdoors between dusk and dawn when mosquitoes are most active.
  • Consider the use of mosquito repellents containing an EPA-registered active ingredient, including DEET, Picaridin, IR3535, oil of lemon eucalyptus, para-methane-diol (PMD), or 2-undecanone when it is necessary to be outdoors.
  • Wear shoes, socks, long pants, and a long-sleeved shirt when outdoors for long periods of time, or when mosquitoes are more active. Clothing should be light-colored and loose-fitting and made of tightly woven materials that keep mosquitoes away from the skin.
  • Be sure door and window screens are tight-fitting and in good repair.
  • Use mosquito netting when sleeping outdoors or in an unscreened structure and to protect infants when outdoors.

EEE is a rare but serious illness in humans with 4-8 cases reported in a typical year in the U.S. The last major outbreak occurred in 2019, involving 38 human cases nationally, with 19 cases occurring in New England. EEE is the most severe mosquito-transmitted disease in the U.S., with approximately 40 percent mortality and significant brain damage in most survivors.

West Nile virus is the most common mosquito-borne viral disease in the United States and occurs every summer in Connecticut. One hundred eighty-one human cases of West Nile virus, including four fatalities, have been reported in Connecticut residents since 2000.

Connecticut Mosquito Management Program

The response to mosquito transmitted diseases in Connecticut is a collaborative inter-agency effort involving the Department of Energy and Environmental Protection (DEEP), The Connecticut Agricultural Experiment Station (CAES), the Department of Public Health (DPH), the Department of Agriculture, and the Department of Pathobiology at the University of Connecticut (UCONN). These agencies are responsible for monitoring mosquito populations and the potential public health threat of mosquito-borne diseases.

The CAES maintains a network of 108 mosquito-trapping stations in 88 municipalities throughout the state. CAES begins mosquito trapping and testing in June and continues into October. Positive findings are reported to local health departments and on the CAES website.

For information on WNV and other mosquito-borne diseases, what can be done to prevent getting bitten by mosquitoes, the latest mosquito test results, and human infections, visit the Connecticut Mosquito Management Program website.