A person over the age of 50 living in the Town of Islip has contracted West Nile virus, according to the Suffolk County Department of Health Services.
The case now marks the third human case of the virus in Suffolk County this season.
West Nile is transmitted from the bite of an infected mosquito and about 20% of those who become infected actually develop symptoms, according to the department.
The agency says those at risk of severe infection are those older than 50 and people with chronic illness or compromised immune systems.
Suffolk County residents are being urged to take precautions against being bitten during the remainder of mosquito season, which extends from June through November.