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

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 until the end of October. The first test results will be available the week of June 7.

“The mosquito monitoring program serves as an effective early warning system to detect and assess the risk of mosquito-borne diseases in Connecticut,” said Dr. Philip Armstrong, Medical Entomologist at CAES. “We will be trapping mosquitoes in 108 locations statewide from now until October. Typically, we first detect West Nile virus-infected mosquitoes in early July, while EEE virus emerges later in the summer.”

“Mosquito-borne diseases, such as EEE and West Nile virus infection, can cause life-threatening neuro-invasive disease, including encephalitis and meningitis. During the summer and into early fall, we encourage residents to take precautions to avoid being bitten by mosquitoes,” said Dr. Jocelyn Mullins, State Public Health Veterinarian, Department of Public Health. “Using an EPA-approved 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, WNV was detected in 143 mosquito pools from 21 towns in Fairfield, Hartford, and New Haven Counties. Eight confirmed human cases of WNV infection were reported from Fairfield, Hartford, and New Haven Counties, with dates of onset from July 10 to October 1. 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.

During 2020, EEE virus was detected in mosquitoes collected from two towns in New London and Windham Counties. There were no EEE infections reported in humans or horses. 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 4 cases (3 fatalities) occurring in Connecticut.

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 at

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 web site at

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