State of Connecticut Mosquito Management Program
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08/19/2026

State Reports Expansion of West Nile Virus

Positive Mosquitoes Identified in 22 Connecticut Towns

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

New Haven, CT – The State Mosquito Management Program is warning Connecticut residents about the increasing risk of infection by West Nile virus (WNV) this season. So far, the Connecticut Agricultural Experiment Station (CAES) has detected WNV-infected mosquitoes in 22 towns: Branford, Bridgeport, Cheshire, Danbury, Darien, East Haven, Fairfield, Greenwich, Manchester, Meriden, Milford, Montville, New Britain, New Haven, North Branford, North Haven, Norwalk, South Windsor, Stamford, Stratford, West Haven, and Westport. There are no reported human cases of WNV so far this season.

“West Nile virus is spreading to additional towns across Connecticut with highest levels of virus activity in mosquitoes from Fairfield and New Haven counties,” said John Shepard, Medical Entomologist at CAES. “We expect mosquito infections to continue to increase, raising the risk of human infection from now through the end of September.”

“Now is the time to take precautions against mosquito bites,” said Dr. Philip Armstrong, Chief Scientist at CAES. "We encourage everyone to protect themselves by using insect repellent and covering exposed skin, 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.

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. The virus is detected in the Northeast every summer and has become the leading cause of mosquito-borne disease in the region.

In 2025, six Connecticut residents were hospitalized with WNV disease; one death was reported among these. Most human infections are acquired from mosquito bites occurring during July through September. The majority of people infected with WNV do not develop symptoms. Approximately 80% of infected individuals remain asymptomatic, while about 20% develop a mild illness characterized by symptoms such as fever, headache, body aches, joint pain, vomiting, diarrhea, or rash. Fewer than 1% of infected individuals develop severe neuroinvasive disease, which can affect the brain, spinal cord, or surrounding tissues and may result in hospitalization, long-term neurological complications, or death.

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 Connecticut 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.

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. Positive findings are reported to local health departments and on the CAES website.

For information on WNV and Eastern equine encephalitis (EEE), what can be done to prevent being bitten by mosquitoes, the latest mosquito test results, and human infections, visit the Connecticut Mosquito Management Program website.