State of Connecticut Mosquito Management Program

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06/02/2025

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 2 and lasts until the end of October.

Last year, WNV was detected in 309 mosquito samples from 44 towns in 7 counties in Connecticut. The majority of WNV activity occurred in urban and suburban regions in Fairfield, Hartford, and New Haven counties. Thirteen human cases of WNV-associated illness were reported with dates of onset from July 30 to September 15. 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 detected from 72 mosquito samples from 16 towns in Fairfield, Middlesex, New London, and Windham counties during 2024. Veterinary cases of EEE were reported from 1 horse, a white-tailed deer, and 2 wild birds. There were no human cases reported in Connecticut, but cases were reported from nearby states including all of the New England states, New York, and New Jersey. 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 in the U.S. occurred in 2019 when the number of confirmed human cases rose to 38, with 4 cases (3 fatalities) occurring in Connecticut.

"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."

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.