A batch of mosquitoes in Manchester has tested positive for the West Nile virus - the first one in New Hampshire this year.
The state Department of Health and Human Services says it is collaborating with the city's health department on notifying people about the recent detection.
The virus, along with eastern equine encephalitis, is transmitted from the bite of an infected mosquito. West Nile was first identified in New Hampshire in August 2000.
Symptoms of the virus usually appear within a week after being bitten by an infected mosquito. They can include flu-like illness including fever, muscle aches, headaches, and fatigue. A very small percentage of people can develop central nervous system disease, including meningitis or encephalitis.
"New Hampshire residents and visitors need to make sure they take precautions to prevent being bitten by mosquitoes as we head into the fall, the most risky time of year for mosquito-borne illnesses," said Dr. Benjamin Chan, state epidemiologist.
People are encouraged to use a mosquito repellant that contains 30 percent DEET, wearing long sleeves and pants at dawn and dusk when mosquitoes are most active, and removing standing water from around homes so mosquitoes do not have a place to breed.
The Health Department says repellents with picaridin, IR3535 and some oil of lemon eucalyptus and para-menthane-diol products also provide protection against mosquito bites.
The state's public health lab has tested 3,048 mosquito batches, two animals, and 46 people so far this season for West Nile and EEE. There have been no positive tests for EEE yet this year.
Last year, one mosquito batch tested positive for West Nile in New Hampshire and there were 18 positive batches for EEE.
Three people were determined to have been infected with EEE last year as well, with two fatalities. No one was found to be infected with the West Nile virus.