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Powassan virus spreads through the bite of an infected tick. It can cause symptoms such as fever, vomiting, and weakness.

In this article, we explain Powassan virus in more detail, including how it spreads and the symptoms of the disease that it causes. We also suggest ways to reduce the chance of getting a tick bite.

A tick in a vial that may transmit powassan virus.Share on Pinterest
Image credit: Mironmax Studio / Getty Images.

Powassan virus is a tickborne flavivirus belonging to the Flaviviridae family.

According to the Centers for Disease Control and Prevention (CDC), people contract the Powassan virus relatively rarely, although the number of reported cases has increased in recent years.

One 2017 article mentions that between 1999 and 2016, there were just 98 reported cases of Powassan virus in the United States.

An infection with the virus can cause swelling or inflammation of the brain, known as encephalitis. In some cases, the membranes surrounding the brain and spinal cord can also become inflamed, which is called meningitis.

Powassan virus is related to some mosquito-borne viruses, including yellow fever virus and West Nile virus.

Powassan virus spreads to humans and animals through the bite of an infected tick. Ticks contract the virus when they feed on infected rodents.

Three different types of tick spread Powassan virus:

  • the deer tick, otherwise known as the black-legged tick, or Ixodes scapularis
  • the groundhog tick, or Ixodes cookei
  • the squirrel tick, or Ixodes marxi

Research suggests that the deer tick is primarily responsible for spreading the virus on the East Coast of the U.S. This tick is also responsible for spreading Lyme disease, ehrlichiosis disease, and other diseases.

The groundhog tick is the main vector of the virus in the Midwest and Canada.

For a person to contract a disease from a tick, it needs to stay attached to them for a length of time. Although people do not know the exact minimum time, the Minnesota Department of Health estimate that it is likely less than 12–24 hours.

Where are the ticks located?

According to the CDC, the majority of cases in the U.S. are in the northeastern and Great Lakes regions.

They tend to occur during tick season, which is from late spring to the middle of fall.

Risk factors

The primary risk factor for contracting the Powassan virus is receiving a bite from an infected tick.

People living, working, or spending time outdoors in areas where the Powassan virus is active have the highest risk of contracting it.

The CDC mention that many people with Powassan virus do not develop symptoms. When symptoms do occur, they can take 1–4 weeks to develop.

Symptoms may include:

In severe cases, the virus can cause encephalitis or meningitis. The symptoms of these conditions include:

  • confusion
  • seizures
  • speech difficulties
  • loss of coordination
  • neck pain
  • fever
  • nausea and vomiting

There is no specific treatment for Powassan virus disease.

Those who have severe symptoms will require hospitalization. In the hospital, they may receive:

  • breathing support
  • intravenous (IV) fluids to maintain hydration levels
  • treatment to reduce swelling in the brain

Most people who contract the Powassan virus do not develop symptoms.

However, the CDC say that of those who develop severe symptoms, approximately 10% will not survive. Of those who recover from severe disease, approximately half will experience chronic health issues, such as:

  • loss of muscle strength and mass
  • memory problems
  • recurring headaches

To prevent Powassan virus disease, people should try to avoid tick bites.

A person can do this by taking the following steps in high risk areas:

  • covering up their skin and wearing long-sleeved shirts and long pants when outdoors
  • tucking their shirt into their pants and tucking their pants into their socks
  • choosing light-colored clothing to highlight the presence of ticks before they attach to the skin
  • wearing only closed-toe shoes
  • applying a tick repellent containing DEET to the skin and clothing, or one containing permethrin to the clothing only
  • avoiding grassy and overgrown areas where possible, especially during tick season, which runs from late spring to the middle of fall
  • checking all outdoor equipment for the presence of ticks
  • using appropriate tick treatments regularly on pets and inspecting them daily for ticks

Tick removal

It is important to check the clothes, skin, and hair for ticks after spending time outdoors. Ticks can be tiny, ranging from the size of a poppy seed to a sesame seed, so it is important to be thorough.

To kill any ticks on backpacks, clothing, or other pieces of equipment, wash the affected items and then put them in the tumble dryer on a high heat for 10 minutes. Alternatively, treat fabric items with 0.5% permethrin.

When checking the body, a person should pay special attention to less visible areas of the skin, such as the groin, bellybutton, underarms, and back of the neck. Ticks may also appear in any skinfolds.

If a tick attaches to the skin, it is important to remove it as quickly as possible. Wearing gloves, people can use flat-tipped tweezers to grab the tick by its mouth area, which is the section attached to the skin, and slowly pull it up and out.

Crushing the tick may release infected blood, so a person should put it in a container of rubbing alcohol to kill it instead.

After removing a tick from the skin:

  1. Wash the site of the bite with soap and water.
  2. Clean the tweezers and any other equipment that has come into contact with the tick.
  3. Dispose of the gloves and wash the hands thoroughly with soap and water.
  4. Monitor for signs and symptoms of infection and see a doctor promptly if any symptoms develop.

Doctors typically diagnose Powassan disease by:

  • taking a detailed account of the person’s health and symptoms
  • asking about their travel to high risk regions and any outdoor activities
  • requesting laboratory testing of blood or spinal fluid samples

Individuals should see a doctor if they develop any of the symptoms of Powassan virus disease, especially if they get a tick bite or have spent time in a high risk area.

Powassan virus disease is a relatively rare tickborne disease that causes fever, headache, and other flu-like symptoms. There is no specific treatment or vaccine, but the symptoms are generally treatable if doctors diagnose the viral infection early.

In some people, the disease can cause severe symptoms and complications, including encephalitis and meningitis. It can even be fatal.

The best way to prevent Powassan virus disease is to avoid exposure to ticks and tick bites. If a tick does attach to the skin, it is important to remove it immediately. Individuals who develop symptoms of Powassan virus disease should seek prompt medical attention.


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