PRO/AH/EDR> Powassan virus encephalitis – USA (04): (NH) 2 cases; 1 case Jamestown Canyon virus


A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Mon 25 Sep 2023
Source: NBC Boston [edited]

New Hampshire health officials announced 2 human cases of the Powassan
virus and one case of the Jamestown Canyon virus on Monday [25 Sep
2023], warning that the risk of tick- and mosquito-borne infections
remains high even as temperatures have begun to drop across the

An adult in Rockingham County and a child from Carroll County were
each diagnosed with Powassan virus and an adult from Hillsborough
County was infected with the state’s 1st case of Jamestown Canyon
virus this year [2023], according to the state Department of Health
and Human Services’ Division of Public Health Services.

“Mosquitoes will be with us until the 1st hard frost, and ticks remain
active as long as there is no snow cover and temperatures remain above
freezing,” said Ryan Tannian, chief of the Division of Public Health
Services’ Bureau of Infectious Disease Control. “Preventing the bites
that cause illnesses transmitted by mosquitoes and ticks is a key
factor in reducing the risk for illness.”

New Hampshire has identified 8 cases of Powassan virus since 2013,
when the disease was 1st detected in humans there.

This summer, 14 batches of mosquitos around the state tested positive
for Jamestown Canyon virus. The state has reported a total of 13 human
cases since 2018.

The Powassan virus is transmitted through the bite of the blacklegged
tick. An infected tick only needs to be attached to a person for 15
minutes to transmit the virus. This is the same tick that transmits
Lyme Disease, Anaplasmosis, and Babesiosis. Early symptoms can include
fever, muscle aches, headaches, and fatigue. More serious central
nervous system diseases, including meningitis or encephalitis can also

The Jamestown Canyon virus is transmitted by the bite of an infected
mosquito, and symptoms of infection can include flu-like illness,
fever, muscle aches, headaches, and fatigue. Individuals with
Jamestown Canyon virus can progress to more serious central nervous
system diseases, including meningitis or encephalitis. Other
infections transmitted by mosquitos include Eastern Equine
Encephalitis and West Nile Virus, which also present with symptoms
similar to Jamestown Canyon virus.

There are no vaccines or anti-virus medications to treat Powassan or
Jamestown Canyon virus infections, and experts say the best way to
prevent illness is to avoid tick and mosquito bites.

[Byline: Marc Fortier]

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