Public health officials in Tisbury say they found a mosquito that was positive for West Nile virus during routine trapping last month.
Though this is the second mosquito that has come back positive, the board of health said in a statement Friday that the risk of contracting the virus remains low and there have been no human cases on the Vineyard this year.
The mosquito was collected at Veterans Park on Sept. 29, and the board urged people to remain vigilant while outside.
“Although cooler fall temperatures reduce mosquito activity, mosquitoes can remain active, and the risk of West Nile virus can persist, until the first frost,” the board wrote.
West Nile virus is primarily spread by mosquitoes. Symptoms include fever, headache, body aches, vomiting, diarrhea and rashes. In severe cases the illness can affect the nervous system and result in death.
The first positive mosquito of the season, which was trapped in August, was also in Veterans Park, one of the several different trapping locations on the Vineyard.
The Tisbury board of health recommended people wear insect repellent when they go outdoors and asked people to get rid of any standing water.