Powassan (POW) Virus Disease Fact Sheet

Last Reviewed: July 2023

What is Powassan virus disease?

Powassan (POW) virus disease is rare, but often serious disease caused by a virus that is spread by the bite of infected ticks. The virus is not transmitted directly from person-to-person. The virus is named after Powassan, Ontario where it was first discovered in 1958. It can cause symptoms ranging from mild flu-like symptoms to life threatening encephalitis (inflammation of the brain). In New York State, there are generally 1 to 9 cases of POW virus disease reported each year. Nationally, approximately 239 cases of POW virus disease were reported over the past 10 years (the most up-to-date national statistics can be found at https://www.cdc.gov/powassan/statistics.html). Prevention by following proper precautions to reduce exposure to ticks is the best defense against POW virus disease.

Who gets Powassan virus disease?

POW virus is transmitted by the bite of an infected tick. The chances of being bitten by a tick are greater during times of the year when ticks are most active. Most cases have occurred in the northeastern and Great Lakes regions of the United States during the late spring, early summer, and mid-fall when ticks are most active. People who work outdoors or engage in outdoor activities such as camping/hiking, gardening, time on athletic fields, or playing in grassy and wooded environments are at an increased risk of exposure.

How is Powassan virus spread?

Ticks can become infected with POW virus if they feed on small animals such as mice and other small mammals that are infected. The disease can be spread to humans when an infected tick bites a person. Unlike other tick-borne diseases, a tick can transmit POW virus while being attached to a person for as little as 15 minutes. POW virus disease cannot spread directly from one person to another.

The tick that primarily spreads POW virus to humans is the black-legged tick or deer tick (Ixodes scapularis). This is the same tick responsible for infecting people with Lyme disease. The squirrel tick (Ixodes marxi) and groundhog tick (Ixodes cookei) also have the potential to spread POW virus to people, but these ticks do not typically feed on humans.

What are the signs and symptoms of Powassan virus disease?

Many people who become infected with POW virus do not develop symptoms. However, for those who do, symptoms usually appear within 1 to 4 weeks after the bite of an infected tick occurred. Symptoms can include fever, headache, vomiting, weakness, confusion, loss of coordination, speech difficulties, and seizures. Severe infections are marked by a quicker onset and includes headache, high fever, confusion, tremors, seizures, paralysis, coma or death. POW virus can cause encephalitis (inflammation of the brain) and meningitis (inflammation of the membranes that surround the brain and spinal cord). Half of survivors have permanent neurological symptoms, such as recurrent headaches, muscle wasting and memory problems. Approximately 10% of POW virus encephalitis cases are fatal.

How is Powassan virus disease diagnosed?

Health care providers diagnose infection based on the patient's clinical symptoms and tests of blood or spinal fluid. These tests typically detect antibodies that the immune system makes against the viral infection. If you think you or a family member may have POW virus disease, it is important to consult your healthcare provider.

What is the treatment for Powassan virus disease?

There is no specific medicine to cure or treat POW virus disease. Health care providers will usually attempt to relieve the symptoms of the illness. Supportive care for severe illnesses may include hospitalization, respiratory support, and intravenous fluids.

What can be done to prevent Powassan virus disease?

The best prevention of POW virus disease is through tick bite prevention. Generally, ticks cannot jump or fly onto a person. They wait in vegetation and cling to animals and humans when they brush by. When in a potentially tick-infested habitat (wooded and grassy areas), take special care to prevent tick bites, such as wearing light-colored clothing (for easy tick discovery) and tucking pants into socks and shirt into pants. Check frequently during outdoor activity for ticks on clothing or skin. Brush off any ticks on clothing or skin before skin attachment occurs. (Duct tape or lint rollers can be quite useful in removing ticks from clothing). A thorough check of body surfaces for attached ticks should be done once indoors. For proper tick removal, please watch the video at Tick removal.

Insect repellents can be effective at reducing bites from ticks that can spread disease. If you decide to use a repellent, use only what and how much you need for your situation. More information on repellents can be found at Environmental Protection Agency- insect-repellents.

In addition:

  • Be sure to follow label directions.
  • Try to reduce the use of repellents by dressing in long sleeves and pants tucked into socks or boots.
  • Children should only handle repellents with adult supervision. Adults should apply repellents to their own hands first and then gently spread it on the child's exposed skin. Avoid applying directly to children's hands. After returning indoors, wash your child's treated skin and clothing with soap and water or give the child a bath.
  • Do not apply near eyes, nose or mouth and use sparingly around ears.
  • After returning indoors, wash treated skin with soap and water.

Domestic animals can carry ticks into areas where you live so it is important to check pets for ticks before they enter the home.

How should a tick be removed?

Grasp the mouthparts with tweezers as close as possible to the attachment (skin) site. Be careful not to squeeze, crush or puncture the body of the tick, which may contain infectious fluids. Pull firmly and steadily upward to remove the tick. After removing the tick, thoroughly disinfect the bite site and wash hands. The NYSDOH has created a video on proper tick removal (Proper Tick removal) and a printable card with steps on how to remove ticks (How to Remove a Tick Card). See or call a doctor if there are concerns about incomplete tick removal. Do not attempt to remove ticks by using petroleum jelly, lit cigarettes or other home remedies because these may increase the chance of contracting a tick-borne disease.

What is a Tick actual size?

Deer Ticks (Actual Size): Nymph, Female, Male

Deer Ticks (Actual Size)