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

Expanding Program from 92 to 108 Monitoring Sites

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), will begin June 1. Statewide mosquito trapping will occur at 108 collection sites in 87 municipalities until the end of October. This includes 16 new trapping locations that were added this year to increase coverage in high risk areas for EEE in eastern Connecticut.

"Last year, we experienced a resurgence of EEE virus activity in eastern Connecticut that resulted in four human cases with 3 fatalities. This was part of a region-wide increase that also affected Rhode Island, New Jersey, and Massachusetts," said Dr. Philip Armstrong, Medical Entomologist at CAES. "We fully expect the virus to return this year, so we will be increasing our monitoring efforts in anticipation of this threat."

"Our state-supported program which began in 1997 provides an effective early warning system for timely detection of mosquito-borne diseases and assessing human risk,” said Dr. Jason White, Director, CAES. “Prevention of EEE and West Nile virus relies on robust surveillance and early detection of virus to inform the public and guide disease control measures as warranted.”

"Mosquito-borne diseases, such as EEE and West Nile virus infection, can cause life-threatening neuroinvasive disease, including encephalitis and meningitis. People should take extra precautions to avoid being bitten by mosquitoes,” said Dr. Jocelyn Mullins, State Public Health Veterinarian, Department of Public Health. “When you are outside enjoying the warm weather this summer, take steps to protect yourself from mosquito bites. Using insect repellent, wearing long pants and long sleeves while outside, and avoiding being outdoors during the hours of dusk and dawn are effective ways to help prevent being bitten.”

Last season, EEE was detected in 28 communities in Connecticut with a total of 122 positive mosquito samples. There were four confirmed human cases of EEE and three individuals died. There were also six horse cases reported, all fatal. The majority of EEE virus activity occurred in Middlesex, New London, and Windham counties consistent with prior years. EEE is a rare but serious illness in humans with 4-8 cases reported in a typical year in the U.S. During 2019, the number of confirmed human cases rose to 38, with 19 cases occurring in New England. EEE is the most severe mosquito-transmitted disease in the U.S. with approximately 33 percent mortality and significant brain damage in most survivors.

During 2019, WNV was identified in 82 mosquito pools from 24 towns in five counties in Connecticut. One human case and one horse case of WNV infection were reported in Fairfield County. 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 NYC area in 1999.

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 87 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.

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 at