Connecticut State Department of Public Health

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All mosquitoes collected in state will be tested for
West Nile, EEE and Zika viruses

The State of Connecticut Mosquito Management Program (MMP) announced that the seasonal mosquito trapping and testing program coordinated by the Connecticut Agricultural Experiment Station (CAES) began on June 5th. The program monitors the types, numbers and locations of mosquitoes and tests them for the presence of viruses that can cause illness including West Nile virus (WNV) and eastern equine encephalitis virus (EEE) and Zika virus. First test results will be available the week of June 12. 

"Connecticut has a robust statewide mosquito monitoring program that includes traps and sites selected for each of the mosquito transmitted viruses of public health concern," said Dr. Philip Armstrong of The Connecticut Agricultural Experiment Station. "Historically, WNV infected mosquitoes are identified early to mid-July each year while EEE is not expected until later in the summer. It is unlikely that Zika infected mosquitoes will be identified but we will be testing for it."

"As we enjoy the warm summer weather outdoors, it is important to take precautions to avoid mosquito and tick bites," said Dr. Raul Pino, Commissioner, Department of Public Health. "Let’s also remember that currently the threat of Zika virus infections among Connecticut residents is the result of travel to Zika affected areas and sexual transmission from infected men to their partners, not from local mosquito transmission."

WNV Surveillance
Last season, CAES trapped and tested over 170,000 mosquitoes and identified WNV-positive mosquitoes collected at trap sites in 20 towns in 4 counties (Fairfield, Hartford, New Haven and New London) collected July 6 to September 28. The first were collected in Stamford. The majority of WNV activity was detected in mosquitoes collected from towns in southwestern Connecticut.

The number of human cases varies from year to year depending on a variety of environmental factors. Since 2000, the number of annually acquired infections has ranged from zero in 2004 and 2009 to 21 in 2012; on average there are 6 reported each year. During 2016, one Connecticut resident was reported with WNV-associated illnesses. The patient, 70-79 and a resident of Milford, was diagnosed with encephalitis and hospitalized. While WNV infections are not usually fatal, patients with meningitis or encephalitis may suffer lasting symptoms resulting from neurological damage.

EEE Surveillance
EEE was identified in one pool of mosquitoes collected September 12, 2016 in Voluntown. 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, mostly in the Atlantic and Gulf Coast states. However, it often causes serious neurologic illnesses and fatalities. A Connecticut resident died of an EEE-associated illness in 2013.

Zika Surveillance
Zika virus was introduced into the Western Hemisphere during 2015, spread rapidly in tropical regions of Latin America, the Caribbean Islands and, in 2016 to Florida and Texas. Zika commonly causes fever, rash, conjunctivitis or other mild symptoms and rarely a neurological illness (Guillain-Barré syndrome) among infected people. However, it can also cause serious birth defects when a woman is infected during pregnancy. From February, 2016 to May, 2017, 115 Connecticut residents tested positive for Zika virus infection including 7 pregnant women. All Zika related infections were associated with travel to affected areas out of the state.

The yellow fever mosquito (Aedes aegypti) is the primary mosquito species involved in the Latin American epidemic and does not occur in Connecticut. Another mosquito species, the Asian tiger mosquito (Aedes albopictus), may also transmit Zika virus and it has a more temperate distribution in the U.S. and has been identified in southern Connecticut. Enhanced mosquito surveillance conducted by the CAES collected 2,221 Aedes albopictus mosquitoes in 25 trap sites in 18 towns primarily in lower Fairfield and New Haven counties. No Zika -positive mosquitoes were identified.

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 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. CAES begins mosquito trapping and testing in June and continues into October.

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 www.ct.gov/mosquito.