ESSEX, Vt. — The Vermont Department of Health says a pool of mosquitoes collected in Essex has tested positive for West Nile virus.

The department said Friday that more than 2,000 mosquito pools — or groups of up 50 of mosquitoes of the same species and location — have been tested this year around Vermont. This is the first one to test positive for the virus, which is spread to humans by the bite of an infected mosquito.

The Health Department says most people do not develop any symptoms, which can include fever, headache, body aches, joint pain, vomiting, diarrhea and skin rash.

West Nile virus has been found in mosquitoes in every county in Vermont in the past. The Health Department says 12 cases have been reported in Vermont residents since 2011.