NEWPORT, N.H. — An adult in Newport, New Hampshire has tested positive for the Jamestown Canyon virus, the fifth case of the mosquito-borne disease in the state this year, according to New Hampshire health officials.

The person was hospitalized with left side weakness, unresponsiveness and multiple seizures, officials said Friday.

The virus is transmitted by the bite of an infected mosquito. There are no vaccines for it and treatment consists of supportive care.

Many illnesses caused by it are mild, but moderate-to-severe central nervous system involvement requiring hospitalization have been reported, including fatal infections.

Early symptoms can include flu-like illness with symptoms like fever, muscle aches, headaches, and fatigue.

“Although JCV is still a rare disease, we are seeing more infections in NH, which is concerning,” Dr. Benjamin Chan, a state epidemiologist, said in a statement. “The risk for mosquito-transmitted infections is present from when snow melts in the spring until there is a mosquito killing frost in the fall.”