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First human case of Jamestown Canyon virus found in New Hampshire this year, officials say

The first human case of Jamestown Canyon virus this year has been identified in New Hampshire, where public health officials have also discovered two cases of Powassan virus, both of which are spread by bites from insects.

A virus spread by mosquito bites, JCV was identified in an adult in HIllsborough County, the Division of Public Health Services said Monday.

The Powassan virus was discovered in an adult in Rockingham County and a child from Carroll County, the agency said. The virus is spread through bites from blacklegged ticks, the agency said.

There are no vaccines or antivirus medications for either illness, the agency said.


“Mosquitoes will be with us until the first hard frost, and ticks remain active as long as there is no snow cover and temperatures remain above freezing,” Ryan Tannian, chief of the agency’s Bureau of Infectious Disease Control, said in a statement. “Preventing the bites that cause illnesses transmitted by mosquitoes and ticks is a key factor in reducing the risk for illness.”

New Hampshire is the fourth state to report a human case of JCV this year, according to the Centers for Disease Control and Prevention. The mosquito-borne illness is most frequently found in the Upper Midwest but has also been found this year in New York, Michigan, and Wisconsin. Including New Hampshire, eight cases have been reported nationwide, the CDC said.

“Fever, headache, and fatigue are common symptoms with Jamestown Canyon virus disease,” the CDC said. “Jamestown Canyon virus can cause severe disease, including encephalitis (inflammation of the brain).”

Human cases of Powassan virus have been reported in nine states this year, including Massachusetts, Connecticut, Maine, and Rhode Island, according to the CDC. A total of 24 cases were reported as of Sept. 19.

Someone may not notice symptoms of Powassan virus for a week or more after being bit by a tick, the CDC said. Severe forms of the illness are fatal in one out of 10 people. Survivors of severe cases face “long-term health problems such as recurring headaches, loss of muscle mass and strength, and memory problems,“ the CDC said.


New Hampshire has reported 13 human cases of JCV since 2018, officials said. The state has identified eight Powassan virus cases since 2013, when the disease was first detected in humans in New Hampshire, officials said.

John R. Ellement can be reached at Follow him @JREbosglobe.