Powassan Virus

What is Powassan virus?

Powassan virus disease is an illness you get from a tick bite. Many people have Powassan virus without any symptoms, but sometimes it causes Powassan virus encephalitis. Encephalitis is brain swelling that can lead to permanent neurological conditions, like memory issues and paralysis. In some cases, it can be fatal.

Powassan virus is named after Powassan, Ontario, the area of Canada where the first case was identified in 1958.

How common is Powassan virus disease?

Powassan virus disease is rare. There have only been about 200 reported cases in the U.S. since 2012.

Is Powassan virus the same as Lyme disease?

No. Powassan virus disease and Lyme disease are both carried by the same type of ticks but they’re different illnesses. Lyme is a bacterial illness that’s more common than Powassan virus.

What are the symptoms of Powassan virus disease?

Symptoms of a Powassan virus infection include:

• Fever.
• Headache.
• Vomiting.
• Fatigue.
• Confusion or altered mental state.
• Seizures.
• Difficulty speaking.
• Paralysis.

Common symptoms, like fever and headache, might come first, followed by more severe symptoms, like confusion or seizures.

What’s the incubation period for Powassan virus?

The incubation period for Powassan virus disease is between one week and one month. This means from the time an infected tick bites you, it usually takes one to four weeks to have symptoms.

What causes Powassan virus disease?

A type of flavivirus (an RNA virus usually spread by mosquitoes and ticks) causes Powassan virus infections. The viruses that cause dengue fever, West Nile and Zika infections are also types of flavivirus.

How does Powassan virus spread?

You get Powassan virus from the bite of an infected Ixodes tick. Ixodes scapularis, commonly called blacklegged or deer ticks, are the most likely to spread it to people. Ixodes cookei (groundhog tick) and Ixodes marxi (squirrel tick) also carry Powassan virus, but they rarely bite people. Unlike some other tick-borne illnesses, a tick only needs to attach to you for a few minutes to infect you with Powassan virus.

Where is Powassan virus found?

Powassan virus infections happen most often in parts of Russia, the U.S. Northeast, and the Great Lakes region in the U.S. and Canada. The highest number of cases have been reported in:

• Massachusetts.
• Minnesota.
• Wisconsin.
• New York.
• New Jersey.
• Connecticut.
• Maine.

What are the complications of Powassan virus disease?

Powassan virus can spread to your brain from the tick bite in your skin. This can cause encephalitis, or swelling in your brain. Even people who recover can have long-lasting health effects from encephalitis.

How is Powassan virus disease diagnosed?

A provider diagnoses a Powassan virus infection by testing your blood or spinal fluid. They might suspect you have a Powassan virus infection or other tick-borne illness if you:

• Have symptoms of Powassan virus encephalitis.
• Live in or have travelled to an area where Powassan virus spreads.
• Could have been bitten by a tick (even if you don’t remember being bitten).

What tests will be done to diagnose Powassan virus disease?

Your provider might order the following tests to help diagnose Powassan virus:

• Blood tests.
• Spinal tap (lumbar puncture).
• Imaging. Your provider will get pictures of your brain using CT scans (computed tomography scans) or MRI (magnetic resonance imaging) if you have neurological symptoms.

How is Powassan virus treated?

There aren’t any antiviral medications that treat Powassan virus infections. If you have encephalitis, a provider will treat you in the hospital. For mild symptoms, ask your healthcare provider how you can manage your symptoms at home. They might recommend rest, fluids or over-the-counter (OTC) medications.

Specific medications and procedures

If you’re severely ill, providers might treat you at the hospital with:

• Antiseizure medications.
• Supplemental oxygen or mechanical ventilation to help you breathe.
• Intravenous (IV) fluids to keep you hydrated.
• Corticosteroids to reduce swelling.
• Tube feeding if you’re unable to feed yourself.

Can you prevent Powassan virus disease?

Avoiding tick bites is the best way to reduce your risk of Powassan virus. Ways to protect yourself from ticks include:

• Cutting your grass shorter than 5 inches.
• Staying on cleared paths if you’re in the woods.
• Using bug sprays with DEET or other ingredients proven to keep ticks away.
• Using clothing to cover as much of your skin as possible when you’re in the woods or areas with long grass. You can buy special tick-repellant clothing if you’re often in areas with ticks.
• Checking your entire body for ticks after you’ve been outside. You’re most likely to find them in your groin, armpits, and on your neck and head. If possible, have someone else check you in places you can’t see yourself (like your back and scalp).
• Ask your veterinarian about the best way to protect your pets from ticks. Check your pets for ticks often, especially after they’ve been outside.
• Follow directions for safely removing a tick if you find one on you.

Does Powassan virus go away on its own?

Most mild symptoms of Powassan virus disease get better on their own. But if you have Powassan virus encephalitis or other serious complications, you’ll need to be monitored in the hospital. You might need treatments or procedures to help you breathe or to reduce swelling.

Outlook for Powassan virus

Even after recovering from the virus, about half of people who had severe illness, including Powassan virus encephalitis, have long-lasting health conditions. These include:

• Paralysis of one side of your face (hemiplegia).
• Memory problems.
• Weakness.
• Loss of muscle (wasting).

What’s the mortality rate of Powassan virus disease?

About 10% of people who get a brain or spinal cord infection from Powassan virus die from it. There’ve been no known deaths from mild Powassan virus.

When should I see my healthcare provider?

See a healthcare provider if you:

• Have been bitten by a tick. There’s no preventive treatment for Powassan virus, but a provider can tell you if you need to be treated for other tick-borne illnesses.
• Have been in an area with ticks (even if you don’t remember being bitten) and have symptoms of Powassan virus.

When should I go to the emergency room?

Go to the nearest ER if you have signs of serious illness, including:

• Confusion or other mental changes.
• Seizures.
• Difficulty speaking.
• Paralysis.

What questions should I ask my healthcare provider?

It might be helpful to ask a provider:

• How do I take care of myself at home?
• What new or worsening symptoms should I look out for?
• How soon should I feel better?
• When should I follow up with you?

A note from Cleveland Clinic

It might seem like every day there’s a new reason to worry about ticks. It’s worth avoiding them, if possible, since the diseases they spread can cause serious complications. If you’re often in areas that have ticks, know how to prevent bites and safely remove ticks you find on you. Still, Powassan virus infections are rare, and experts think most people who get them have mild or no symptoms.

If a tick does bite you, don’t panic. Talk to a healthcare provider and be on the lookout for symptoms. While there’s no specific treatment for Powassan virus infections, knowing the signs of serious illness means you can get help quickly if you need it.