What Is Powassan?

Powassan is a rare tick-borne disease caused by a virus. It can cause swelling in the brain (doctors call this encephalitis) and in the membranes around the brain and spinal cord (you may hear this called meningitis).

Only about 75 cases were reported in the U.S. over the last 10 years. Yet experts warn the disease could start to spread faster now that it's transmitted by the deer tick -- the same tick that spreads Lyme disease.

Powassan spreads from ticks to people faster than Lyme disease. Although the viral infection is usually mild, it can be life-threatening in a small number of people, and in severe cases, some symptoms, like weakness and memory loss, can be permanent.

That's why health officials caution people who live in Northeast and Great Lakes states, where the virus often spreads, to take steps to avoid infection.

How It Spreads

Infected ticks spread the Powassan virus when they bite people. In the past, types of ticks that rarely bite humans -- such as woodchuck ticks and others -- mainly spread it. But now, the deer tick, which is more likely to bite people, also carries the virus.

The ticks that carry Powassan mainly live in wooded areas around the Northeast and Great Lakes. These ticks are most active in late spring, early summer, and mid-fall.

Not every tick is infected with the virus, and not everyone who is bitten will get sick. But ticks that are infected can transmit it quickly -- within minutes of attaching to a person. Lyme disease takes much longer -- 24 to 48 hours -- to spread from tick to human.

You can't catch Powassan from another person.

Symptoms

Most Powassan infections are mild. Some people don't have any symptoms. If you do, they'll show up a week to a month after you were bitten and may include:

See your doctor if you have any of these symptoms and might have been exposed to ticks. Call 911 or go to an emergency room for severe symptoms.

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Diagnosis

Your doctor will ask you questions like these:

  • What symptoms do you have?
  • When did they start?
  • Could you have been exposed to ticks?

You might need tests of your blood and spinal fluid to check for antibodies that your immune system makes to fight the Powassan virus.

Treatment

Although no specific drug or procedure treats Powassan, and many cases are mild, doctors have ways to manage symptoms. If yours are severe, you might need to go to a hospital to get care, such as:

  • Breathing support
  • Fluids through a vein (IV)
  • Medicine to bring down swelling in the brain

 

Prevention

The best way to protect yourself from Powassan and other tick-borne diseases is to avoid tick bites:

  • Stay out of wooded or grassy areas whenever you can.
  • When you are in the woods, spray all areas of your bare skin with an insect repellent containing DEET. Also, treat your clothes and gear with permethrin. Keep in mind that repellents only last for a few hours.
  • When you come back inside, check your whole body for ticks. Don't forget about your scalp.
  • Also, check your clothes and pets.
  • Take a bath or shower to find and wash off any ticks on your skin.

There's no vaccine that can prevent the illness.

WebMD Medical Reference Reviewed by Neha Pathak, MD on May 09, 2017

Sources

CDC: "Frequently Asked Questions: What is Powassan virus disease?" "Powassan Virus." "Powassan Virus: Symptoms."

Maine Public: "Researchers Urge Caution As Powassan Virus Spreads in Ticks Along Coast."

Minnesota Department of Health: "Powassan (POW) Virus Basics."

Yale Public Health: "The Rise of Powassan Virus."

UpToDate: “Arthropod-borne encephalitides.”

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