The Vermont Health Department says West Nile virus has been detected in a mosquito pool in the Addison County town of Whiting.
One West Nile sample tested positive for the virus and four samples were found with Eastern Equine Encephalitis.
The last human case of West Nile Virus in Vermont was in 2003.
No human cases of Eastern Equine Encephalitis have been detected in Vermont.
Both viruses are spread by the bite of an infected mosquito.
State Epidemiologist Patsy Kelso says the detection of the viruses is a reminder that people should avoid mosquito bites.
Most infected people have no symptoms of West Nile. About 20 percent of those infected have symptoms such as fever, headache, body aches, nausea, and vomiting. In rare cases the virus is fatal.