New Hampshire health officials reported today that an adult from Bow, NH, tested positive for Jamestown Canyon virus (JCV). This is the second JCV case seen in 2020.


The person was not hospitalized and is doing well, but experienced fever and mild neurological symptoms. JCV is transmitted by the bite of an infected mosquito. There are no vaccines to prevent JCV and treatment consists of supportive care.

“Jamestown Canyon Virus is one of three different infections that can be transmitted through the bite of a mosquito in New Hampshire,” said Dr. Benjamin Chan, NH State Epidemiologist. “This is the second infection identified in NH this year, and the risk for mosquito-transmitted infections will only increase through the summer and fall until there is a mosquito-killing hard frost. New Hampshire residents and visitors need to continue to take steps to protect themselves from mosquito bites.”

Jamestown Canyon virus is a mosquito-borne pathogen that circulates widely in North America primarily between deer and mosquitoes but can also infect humans. Reports in humans have been increasing over the last several years as recognition and testing for this virus has increased. This is New Hampshire’s eleventh case of JCV since the first report of the disease in the State in 2013. Many illnesses caused by JCV are mild, but moderate-to-severe central nervous system involvement requiring hospitalization have been reported, including fatal infections.

The arboviral risk level for Bow will be increased to high. The arboviral risk level indicates the risk of transmission of these infections to people from mosquitoes. The surrounding towns of Goffstown, Dunbarton, Hopkinton, and Allenstown will increase to moderate. The risk level for the surrounding towns of Hooksett, Pembroke and Concord will remain moderate.