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State Reports Expansion of West Nile Virus: Positive Mosquitoes Identified in Eight More Connecticut Towns

The Connecticut Agricultural Experiment Station (CAES) has identified West Nile virus (WNV) infected mosquitoes in eight new towns: Bethany, Franklin, Greenwich, Madison, New Haven, Waterford, West Haven, and Weston.  The mosquitoes were trapped from July 12 to July 19, 2018.  WNV positive mosquitoes were also identified in Bridgeport, Darien, Easton, New Canaan, Stamford, Stratford, and Waterbury earlier this year.

“We are seeing a major expansion and build-up of West Nile virus in the mosquito population” said Dr. Philip Armstrong, Medical Entomologist at the CAES. “We are also detecting the virus in human-biting mosquitoes comparatively early in the season, which substantially increases the risk of infection.”

"The current warm weather and high humidity provide ideal conditions for further amplification of West Nile virus and this is likely to continue as we move into August" said Dr. Theodore Andreadis, Director of CAES.  "We urge everyone to prevent mosquito bites by using insect repellent and covering bare skin, especially during dusk and dawn when mosquitoes are most active.”

No human or horse cases have been reported with WNV-associated illnesses acquired in Connecticut this season. One hundred thirty four human cases of West Nile virus, including three fatalities, have been diagnosed in Connecticut residents since 2000.

The State of Connecticut Mosquito Management Program is a collaborative effort involving the Department of Energy & Environmental Protection, the Connecticut Agricultural Experiment Station, the Department of Public Health, the Department of Agriculture, and the University of Connecticut Department of Pathobiology and Veterinary Science. These agencies are responsible for monitoring the potential public health threat of mosquito-borne diseases.

The CAES maintains a network of 91 mosquito-trapping stations in 72 municipalities throughout the state. Mosquito traps are set Monday – Thursday nights at each site every ten days on a rotating basis. 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 West Nile and eastern equine encephalitis viruses and how to prevent mosquito bites, visit the Connecticut Mosquito Management Program Web site at
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