Powassan virus disease is a rare tick-borne viral infection spread mainly by blacklegged (deer) ticks in the US Northeast and Great Lakes region. Most people who are infected never develop symptoms; when illness does occur it ranges from a mild fever and headache to, rarely, serious inflammation of the brain or its surrounding membranes. It is not spread by the Lone Star tick, and only a licensed clinician can diagnose it.
Last reviewed: 2026-07-20 · Educational only — not medical advice.
Not transmitted by the Lone Star tick. This illness is spread by Blacklegged tick (deer tick), Groundhog tick, Squirrel tick — a different tick. If a Lone Star tick bit you, this is generally not the concern.
What is powassan virus disease?
Powassan is a viral disease caused by the Powassan virus (a flavivirus) and transmitted through the bite of an infected tick. In the United States three tick species spread it: the blacklegged or deer tick (Ixodes scapularis), the groundhog tick (Ixodes cookei), and the squirrel tick (Ixodes marxi). It is uncommon — historically only a small number of cases are reported nationwide each year — but CDC notes reported cases have been increasing in recent years. Powassan is a distinct illness and is not the same as Lyme disease, even though the blacklegged tick can carry both.
Symptoms
Many people infected with Powassan virus have no symptoms at all
Initial symptoms can include fever, headache, vomiting, and weakness
Severe illness (uncommon) can involve inflammation of the brain (encephalitis) or the membranes around the brain and spinal cord (meningitis)
Signs of severe illness include confusion, loss of coordination, difficulty speaking, and seizures
Some survivors of severe illness have long-term problems such as recurring headaches, loss of muscle strength, or memory problems
How soon do symptoms appear?
For people who do develop symptoms, the time from an infected tick's bite to feeling sick (the incubation period) generally ranges from about 1 week to 1 month; many infected people never develop symptoms at all.
Diagnosis
Diagnosis is made by a licensed clinician based on your symptoms, recent tick exposure, where you live or traveled, and laboratory testing of blood or spinal fluid for antibodies to the virus, often coordinated through state health departments or CDC. It cannot be self-diagnosed.
Treatment
There are no medicines that treat Powassan virus specifically and no antiviral cure. Care is supportive — rest, fluids, and over-the-counter pain relief for milder illness; people with severe illness often need hospital care such as respiratory support, IV fluids, and management of brain swelling. A clinician directs any individual plan.
Prevention
There is no vaccine to prevent Powassan, so avoiding tick bites is the key step: use an EPA-registered repellent, wear permethrin-treated clothing, avoid tall grass and leaf litter, and do a full-body tick check after being outdoors. Remove any attached tick promptly with fine-tipped tweezers.
Where it occurs
Most US cases occur in the Northeast and Great Lakes regions, from late spring through mid-fall when ticks are most active. Reported cases are few (historically only a small number — on the order of a few dozen or fewer nationwide per year) but have been rising. Note for our audience: the blacklegged (deer) tick that spreads Powassan is the same tick that spreads Lyme disease — and neither Powassan nor Lyme is transmitted by the Lone Star tick. Rocky Mountain spotted fever is likewise not a Lone Star tick disease; it is spread mainly by the American dog, Rocky Mountain wood, and brown dog ticks.
When to seek care: Contact a clinician if you develop fever, headache, vomiting, or weakness within about a month of a tick bite or outdoor exposure in an area where Powassan occurs. Seek emergency care right away for confusion, a severe or unusual headache, trouble speaking, loss of coordination, or seizures. When in doubt, let a medical professional decide — this page is educational and not a substitute for medical advice. For emergencies such as trouble breathing or anaphylaxis, call emergency services. Educational information only — not medical advice. See our sources and disclaimer.
How soon after a tick bite would Powassan symptoms appear?+
For people who get symptoms, it is usually about 1 week to 1 month after the bite. Many infected people never develop symptoms at all, so the absence of symptoms right after a bite does not rule anything in or out — a clinician can advise you.
Does the Lone Star tick spread Powassan virus?+
No. Powassan is spread by the blacklegged (deer) tick and two other Ixodes ticks (the groundhog tick and squirrel tick). The Lone Star tick does not transmit Powassan — nor does it transmit Lyme disease or Rocky Mountain spotted fever.
Is there a vaccine or a cure for Powassan?+
No. There is no vaccine to prevent Powassan and no antiviral medicine that cures it. Treatment is supportive, and severe cases may require hospitalization. Preventing tick bites is the best protection.
How common and how serious is Powassan?+
It is rare — only a small number of US cases are reported each year, though the count has been rising. Most infections cause no symptoms, but severe brain infection, while uncommon, can be serious. A clinician can assess your individual risk.
Powassan virus is a rare tick-borne infection spread by blacklegged (deer) ticks in the US Northeast and Great Lakes — not the Lone Star tick. Learn the symptoms, the 1-week-to-1-month onset window, and prevention. Educational, not medical advice.
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