Health officials on Martha's Vineyard are investigating an apparent case of Powassan virus, a rare but potentially serious tick-borne illness.

If confirmed, the case would be just the second on the island in the last 20 years, the Martha's Vineyard Boards of Health said Tuesday. If confirmed, it would be the fourth case in Massachusetts this year.

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Deer ticks transmit Powassan, but unlike with other illnesses like Lyme disease, it can be contracted within 15 minutes of a bite.

"There is no specific treatment, vaccine, or cure for Powassan virus disease," Martha's Vineyard health officials wrote in a press release . "Severe cases can cause brain swelling (encephalitis), confusion, seizures, and long-term neurologi

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