State Mosquito Monitoring Program Begins Testing for Mosquito-Borne Viral Diseases

MEDIA CONTACT:
Dr. Philip Armstrong
The Connecticut Agricultural Experiment Station
203-974-8510; Philip.Armstrong@ct.gov

John Shepard
The Connecticut Agricultural Experiment Station
203-974-8517; John.Shepard@ct.gov

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 June 1 and lasts until the end of October.

Last year, WNV was detected in 230 mosquito samples from 37 towns in 6 counties in Connecticut. The majority of WNV activity occurred in urban and suburban regions in Fairfield, Hartford, and New Haven counties. Six human cases of WNV-associated illness were reported with dates of onset from August 10 to September 18. WNV occurs every summer in the Northeast and has become the main cause of mosquito-borne 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 2025. EEE is a rare but serious illness in humans with approximately 40 percent mortality. The last major outbreak occurred in 2024, involving 19 human cases nationally with 13 of these cases reported in each of the New England states other than Connecticut, and 2 each in New York and New Jersey

"Every summer, we trap and test mosquitoes in locations throughout Connecticut to monitor the risk of mosquito-borne diseases throughout the state," said John Shepard, 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.”

“Mosquitoes are more than just a nuisance," said Dr. Philip Armstrong Chief Scientist at CAES. “They can transmit West Nile virus and other serious mosquito-borne illnesses. 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."

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

Minimize time spent outdoors between dusk and dawn when mosquitoes are most active.
When it is necessary to be outdoors, use mosquito repellents containing an EPA-registered active ingredient, including DEET, Picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol (PMD), or 2-undecanone. EPA registration of skin-applied repellent products indicates that they have been evaluated and approved for human safety and effectiveness when applied according to instructions on the label.
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.
Wear clothing and gear treated with permethrin. Permethrin is an insecticide that kills or repels mosquitoes and ticks.
Be sure door and window screens are tight-fitting and in good repair.
When sleeping outdoors, use tents or mosquito netting in an unscreened structure. Treat camping gear with permethrin when possible.
Cover strollers and baby carriers with mosquito nets when outside.

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 Connecticut Veterinary Medical Diagnostic Laboratory (CVMDL) 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 10 days on a rotating basis and then at least once a week after detection of virus. Mosquitoes are grouped (pooled) for testing according to species, collection site, and date.

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 website.