A mosquito sample taken from Westport last week has tested positive for West Nile Virus.

The positive finding was announced Wednesday by the state Department of Public Health, and comes to weeks after a positive sample was obtained in Tiverton by public health officials in that state. So far this year, three Massachusetts residents have contracted the virus, but none are in this area of the state.

Humans can only contract the virus through a bite from an infected mosquito, and Westport residents should continue protecting themselves from mosquito bites until the first hard frost of autumn.

West Nile Virus is the leading cause of mosquito-borne disease in the continental United States. There are no vaccines to prevent or medications to treat the virus in people.

Fortunately, most infected with West Nile do not feel sick, though about one in five people who are infected develop a fever and other symptoms. About one out of 150 infected people develop a serious, sometimes fatal, illness.