Powassan virus disease

Powassan virus disease is caused by the Powassan virus (a flavivirus) and spread through the bite of an infected tick. In the US, three tick species spread it. They are the blacklegged or deer tick (Ixodes scapularis), the groundhog tick (Ixodes cookei), and the squirrel tick (Ixodes marxi). It is uncommon. In the past, only a small number of cases were reported across the US each year. But CDC notes reported cases have been rising in recent years. Powassan is a separate illness and is not the same as Lyme disease, even though the blacklegged tick can carry both.

• Many people infected with Powassan virus have no symptoms at all
• First symptoms can include fever, headache, vomiting, and weakness
• Severe illness is uncommon. It can cause inflammation of the brain (encephalitis) or of the membranes around the brain and spinal cord (meningitis)
• Signs of severe illness include confusion, loss of coordination, trouble speaking, and seizures
• Some people who survive severe illness have lasting problems. These can include repeated headaches, loss of muscle strength, or memory problems

For people who do get symptoms, the time from an infected tick's bite to feeling sick (the incubation period) usually ranges from about 1 week to 1 month. Many infected people never get symptoms at all.

A licensed doctor makes the diagnosis based on your symptoms, recent tick exposure, and where you live or traveled. Lab tests of blood or spinal fluid look for antibodies to the virus. These tests are often arranged through state health departments or CDC. You cannot diagnose it yourself.

No medicine treats Powassan virus itself, and there is 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 help breathing, IV fluids, and treatment for brain swelling. A doctor directs each person's care plan.

There is no vaccine to prevent Powassan, so avoiding tick bites is the key step. Use an EPA-registered repellent and wear permethrin-treated clothing. Avoid tall grass and leaf litter, and check your whole body for ticks after being outdoors. Remove any attached tick right away with fine-tipped tweezers.

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 but rising. In the past there were only a small number, on the order of a few dozen or fewer per year across the US. Note: the blacklegged (deer) tick that spreads Powassan is the same tick that spreads Lyme disease. Neither Powassan nor Lyme is spread by the Lone Star tick. Rocky Mountain spotted fever is also not a Lone Star tick disease. It is spread mainly by the American dog, Rocky Mountain wood, and brown dog ticks.