Connecticut Department of Public Health

05/31/2023 | Press release | Distributed by Public on 05/31/2023 14:15

State mosquito monitoring program begins testing for mosquito-borne viral diseases

Press Releases


State mosquito monitoring program begins testing for mosquito-borne viral diseases


Wednesday May 31, 2023


Philip Armstrong, ScD

Research Scientist

The Connecticut Agricultural Experiment Station

123 Huntington Street New Haven, CT 06511


[email protected]

New Haven, CT - The State of Connecticut Mosquito Management Program today announced it is monitoring mosquitoes for the presence of viruses that can cause illness in people including West Nile virus (WNV) and eastern equine encephalitis (EEE) virus. The mosquito trapping and testing program, coordinated by The Connecticut Agricultural Experiment Station (CAES), begins May 30 until the end of October.

Each summer, we trap and test mosquitoes in locations throughout Connecticut to monitor the risk of mosquitoborne diseases throughout the state." said Dr. Philip Armstrong, Medical Entomologist at CAES. "Typically, West Nile virus activity peaks from July-September and occurs primarily in urban and suburban communities in the state. EEE virus transmission, in contrast, is more unpredictable from year to year and occurs later in the season, primarily in rural communities in southeastern Connecticut."

Last season, WNV was detected in 185 mosquito pools from 24 towns in six counties in Connecticut. The majority of WNV activity was detected in densely populated urban and suburban regions in Fairfield, Hartford, and New Haven counties. Seven human cases of WNV-associated illness were reported with dates of onset from August 11 to September 20. WNV occurs every summer in the Northeast and has become the main cause of mosquitoborne illness in this region since it was first introduced into the New York City area in 1999.

EEE virus was not detected in the state during 2022. 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 when the number of confirmed human cases rose to 38 with 4 cases (3 fatalities) occurring in Connecticut.

"While we should all be outside enjoying the great weather, I want to encourage everyone to follow some best practices to prevent mosquito bites," said Connecticut Department of Public Health Commissioner Manisha Juthani, MD. "You can become very ill from WNV or other mosquito-borne illnesses. This goes for any age although anyone over the age of 60 is at a greater risk. Taking some simple steps can make a vital difference."

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

• Minimize time spent outdoors between dusk and dawn when mosquitoes are most active.

• Be sure door and window screens are tight-fitting and in good repair.

• 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 made of tightly woven materials that keep mosquitoes away from the skin.

• Use mosquito netting when sleeping outdoors or in an unscreened structure and to protect small babies when outdoors.

• Consider the use of an EPA-registered mosquito repellent, according to directions, when it is necessary to be outdoors.

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. Mosquito traps are set Monday - Thursday nights at each site every ten days on a rotating basis and then twice a week after detection of virus. Mosquitoes are grouped (pooled) for testing according to species, collection site, and date. Positive findings are reported to local health departments and on the CAES website at

For information on WNV and EEE, what can be done to prevent getting bitten by mosquitoes, the latest mosquito test results and human infections, visit the Connecticut Mosquito Management Program web site at