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

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 virus (EEE). The mosquito trapping and testing program, coordinated by The Connecticut Agricultural Experiment Station (CAES), will begin June 4. First test results will be available the week of June 11.
"We will trap and test mosquitoes at 91 locations statewide from now until October", said Dr. Philip Armstrong Medical Entomologist at CAES. "Typically, we first detect West Nile virus-infected mosquitoes in early to mid-July but the highest levels of activity occur from mid-August through September, especially along the suburban-urban corridor in southwestern CT from Greenwich to New Haven and the greater Hartford area.  Eastern equine encephalitis virus activity, which is generally confined to the southwestern region of the state is not anticipated until later in the summer."
“The detection of West Nile virus in mosquitoes occurs each summer, but reduction of mosquito breeding habitats can greatly lessen the potential for West Nile virus to become a significant human health threat,” said Dr. Theodore Andreadis, Director of CAES. “We strongly encourage homeowners and communities to eliminate standing water available for mosquito breeding around the home, ensure that door and window screens are tight-fitting and in good repair, and consider the use of mosquito repellent, especially between dusk and dawn when mosquitoes are most active”.
Last season, CAES trapped and tested nearly 200,000 mosquitoes and identified WNV-positive mosquitoes at trap sites in 30 towns in 6 counties (Fairfield, Hartford, Middlesex, New Haven, New London, and Windham). As in prior years, the majority of WNV activity was detected in urban and suburban regions in southwestern (Fairfield and New Haven counties) and central Connecticut (Hartford County). 
The Department of Public Health investigates all potential human cases of WNV and EEE infection while veterinary cases are investigated by the Department of Agriculture. During 2017, three people were reported with WNV-associated illnesses; they were residents of Stamford and New Haven. Clinical syndromes included WNV fever, meningitis, and acute flaccid paralysis. Dates of onset of symptoms were from August 22 to August 30. There were no fatalities. While WNV infections are usually not fatal, patients with meningitis or encephalitis may suffer long lasting symptoms of the nervous system.  In addition, a single horse case of WN virus infection occurred in Fairfield County with date on onset on October 23.  Since 2000, 134 human cases of WNV have been confirmed in the State including three fatalities.
During 2017, EEE virus was identified in six mosquito pools in three towns in New London and Windham counties.   No human or domestic animal infections were reported. EEE is a rare illness in humans, and only a few cases are reported in the United States each year. Most cases occur in the Atlantic and Gulf Coast states. EEE is the most severe mosquito-transmitted disease in the United States with approximately 33 percent mortality and significant brain damage in most survivors.  A Connecticut resident died of EEE infection in 2013.
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 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 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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