Yale Daily News

Connecticut scientists identified mosquitos carrying West Nile Virus and others carrying Eastern Equine Encephalitis in early August. 

Researchers at the Connecticut Agricultural Experiment Station, or CAES, identified the first mosquito sample to test positive for West Nile Virus on Jul 8. Since this time, 141 mosquitos carrying West Nile Virus, or WNV, have been identified, resulting in six human cases of the virus. The first mosquito that tested positive for Eastern Equine Encephalitis, or EEE, was trapped at Stonington High School on Aug. 3, followed by a second mosquito collected from the town of Hampton on Aug. 12. 

“Both West Nile Virus and Triple E can cause neuroinvasive disease,” said Philip Armstrong, director of the Connecticut Mosquito and Arbovirus Surveillance Program. “Some people might develop a mild flu-like illness or no symptoms and make a full recovery without having to seek medical care. But for the individuals that develop neuroinvasive disease, it’s a very serious illness.” 

Yale School of Medicine professor Joseph Vinetz described the symptoms of EEE in further detail. He explained that approximately 2 percent of infected adults and roughly 2 to 7 percent of infected children may develop encephalitis, a form of inflammation in the brain. Once these neurological symptoms begin, there is a rapid deterioration in the condition of the patient. He estimated that approximately 90 percent of individuals with severe cases of EEE would become comatose, while half may develop seizures, signaling brain dysfunction. 

While no human cases of EEE have been reported this year in Connecticut, Vinetz and Armstrong identified the populations that would be most at risk. Armstrong explained that all age groups are susceptible to the disease, while Vinetz mentioned that young children and older adults are at an even higher risk of developing neurological sequelae after EEE exposure.

“Last year we had an unprecedented outbreak of Triple E in the region, and that included four human cases in Connecticut,” Armstrong said. “Three of the four were fatalities and the fourth individual developed very debilitating symptoms and is still in recovery. But as far as who develops the illness, it’s really all age groups, unlike say West Nile Virus …  which tends to affect the elderly more severely.”

Joseph Fauver, a postdoctoral research associate studying arboviruses at the School of Public Health, described how people can protect themselves from EEE and WNV mosquitoes this fall. 

He mentioned that the most effective way to reduce the risk of contracting either virus is to prevent exposure to mosquito bites. 

“Wear long sleeve clothing … wear EPA registered insect repellents such as DEET and reduce mosquito breeding sites around your home,” Fauver wrote in an email to the News. 

Armstrong added that people should particularly limit exposure to shady, wooded areas and swamps between dusk and dawn when the mosquitoes are most active.  

Though the CAES continues to detect West Nile Virus samples in their collections, Armstrong emphasized that the public need not worry. He mentioned that due to the drought in Connecticut this year, much of the EEE virus activity has been curtailed in comparison to the 2019 cycle. In addition, the end of mosquito season is in sight, signifying a declining risk of WNV transmission. 

“What you really need is that hard frost, that killing frost, that will shut things down. Usually, that is some time in October,” Armstrong said.

The most common species of mosquito that carries EEE is Culiseta melanura

Sydney Gray | sydney.gray@yale.edu