The ticks that carry Lyme disease may be even more dangerous than you thought. They also can carry a virus that can cause a potentially fatal disease called Powassan virus encephalitis. And warmer winters may lead to rising tick populations, increasing the risk. It also is possible that other ticks may carry the virus.
It can take a tick as little as 15 minutes to transmit Powassan encephalitis to a person. Most people who contract it have no symptoms. But infections that do cause symptoms are extremely serious—10% to 15% of people who develop symptoms do not survive.
Symptoms usually start with fever and a sense of generally feeling unwell, with a series of nonspecific flulike muscle aches and pains and sometimes a rash or headache. This is followed a few days to a few weeks later by severe headache, weakness, possible seizures, inability to think clearly and possibly inability to breathe on one’s own.
Everyone with symptomatic Powassan encephalitis should be hospitalized. Treatment includes mechanical ventilation, blood pressure support and management of electrolytes. There is no vaccine to prevent Powassan encephalitis, and there are no medicines to cure it. With prompt care, patients typically recover after a few days to a few weeks, but at least half of those who survive will have permanent neurological damage. Permanent effects may include seizures, cognitive disability, weakness or loss of sensation in limbs or coordination difficulties.
Powassan encephalitis can strike anyone—many cases are in otherwise perfectly healthy individuals. For now, the disease, thankfully, is rare. The Centers for Disease Control and Prevention estimate only about 75 cases nationwide over the past decade, mostly in the Great Lakes region and the Northeast. There is no evidence that pets can get encephalitis due to the Powassan virus, but they can carry ticks into the house.
Self-defense: If you are likely to be in areas with ticks, use an insect repellent that contains DEET. Also wear permethrin-embedded clothing—and choose light-colored garments to see ticks.