Powassan Virus

Fact sheet about powassan virus

What is Powassan virus?

Powassan virus is a tickborne virus that is spread by infected blacklegged (deer) ticks, which also carry the germs that cause Lyme disease, babesiosis and anaplasmosis. The disease is rare but often serious. 

How is Powassan virus spread?

It’s spread by the bite of an infected tick. While ticks must be attached for a certain length of time before they can spread infections, there is evidence that Powassan virus can spread from the tick into a person in as little as 15 minutes after attachment.

What are the symptoms of Powassan virus?

Although most people who are exposed to Powassan virus likely never feel ill, others may become severely ill with meningitis (inflammation of the covering of the brain and spinal cord) or encephalitis (inflammation of the brain). Symptoms can include fever, headache, double vision, vomiting, confusion, loss of coordination, speech difficulties and seizures. Approximately 10% of people with this severe form of disease will die and survivors may have long term health consequences. 

How soon do symptoms of Powassan virus appear?

Symptoms of disease usually begin between one to five weeks after the bite of an infected tick.

How is Powassan virus diagnosed?

Serum (a component of blood) or cerebrospinal fluid (CSF) can be collected and tested for antibodies against the virus or for viral genetic material.

How is Powassan virus treated?

There is no specific treatment once infection with Powassan virus has occurred. Treatment consists of supportive care, rest, and fluids to prevent dehydration.  

Where does Powassan virus occur?

In the United States, most cases occur in the Northeast and Upper Midwest regions. From 2013-2025, Massachusetts reported 84 cases. For the most up to date state data, see our website Mass.gov | Tick Borne Disease Surveillance Data.

Is there a seasonality (time of year) one is more likely to get Powassan virus?

Cases of Powassan virus can occur any time ticks are active. Young ticks (nymphs) are most active during the warm weather between May and July. Adult ticks are most active during the fall and spring but may also be out searching for a host any time that temperatures are above freezing. 

How can you prevent Powassan virus infection?

Prevention begins with you! Take steps to reduce your chances of being bitten by any tick. Ticks are most active during warm weather, late spring through fall. However, ticks can be out any time that temperatures are above freezing. Ticks cling to vegetation and are most numerous in brushy, wooded, or grassy habitats. When you are outside in an area likely to have ticks (e.g., brushy, wooded, or grassy places), follow these simple steps to protect yourself and your loved ones:

• Use EPA registered tick repellents.
• Products with DEET may be used on skin. Repellents containing DEET should not be used on children less than 2 months of age and should be used in concentrations no higher than 30% on older children.
• Use permethrin products on items such as clothing, shoes, bed nets and camping gear. Permethrin should not be applied to skin.
• Other repellents, such as picaridin, oil of lemon eucalyptus and IR 3535, have also been found to provide protection against ticks. More information on choosing a repellent and how to use repellents safely is included on the DPH Public Health Fact Sheet on Tick Repellents at mass.gov/DPH/Ticks.
• Wear long, light-colored pants tucked into socks or boots, and a long-sleeved shirt. This will help keep ticks away from your skin and help you spot a tick on your clothing faster.
• Stay on trails when walking or hiking, avoiding the edge habitat where ticks are likely to be.
• Talk to your veterinarian about tick control options (tick collars, repellents) for your pets.

After spending time in an area likely to have ticks, check yourself, your children, and pets for ticks. Young ticks, called nymphs, are the size of a poppy seed. Adult ticks are the size of a sesame seed. Both nymph and adult ticks can spread diseases; however, nymphs are more of a concern. They are aggressive feeders and so tiny that it can be difficult to see them on the body unless you look carefully. When doing a tick check, remember that ticks like places that are warm and moist. Always check the back of the knees, armpits, groin, scalp, back of the neck and behind the ears. If you find a tick attached to your body, remove it as soon as possible using fine-point tweezers. Do not squeeze or twist the tick’s body, instead grasp it close to your skin and pull straight out with steady pressure.

Know the symptoms of Powassan virus as described in this fact sheet. If you have been someplace likely to have ticks and develop symptoms of any disease carried by ticks, see your health care provider right away.

Where can I get more information on Powassan virus?

• For questions about your own health, contact your health care provider.
• For questions about diseases spread by ticks, contact DPH at [phone] or online at mass.gov/DPH/Ticks. You may also contact your local Board of Health.
• Health effects of pesticides, DPH, Bureau of Climate and Environmental Health at [phone].
• CDC.gov | Powassan virus