Powassan Virus · What Is It, Causes, Treatment, and More

Powassan virus disease is caused by the bite of a tick that has been infected with Powassan virus. Ticks are the vector of Powassan virus disease and originally contract the virus by biting a reservoir animal, such as a squirrel or mouse, that carries the virus. The virus can be transmitted to humans through the bite of an infected tick. Once the infected tick bites a human, the transmission of the virus occurs very quickly, usually within 15 minutes.  

Three types of ticks (i.e.,  Ixodes cookei, Ixodes marxi, and Ixodes scapularis) can spread Powassan virus. Ixodes cookei (i.e., groundhog tick), along with Ixodes marxi (i.e., squirrel tick), are not known to bite humans. On the other hand, Ixodes scapularis (i.e., black-legged or deer tick), which does bite humans, is primarily responsible for the spread of Powassan virus and other tick-borne infections, such as Lyme disease. Although person-to-person transmission does not occur, Powassan virus can rarely be transmitted through transfusion of infected blood. 

Most individuals infected with the Powassan virus will not experience any signs and symptoms. If symptomatic, however, clinical manifestations may include fever, headache, weakness, and vomiting. In more severe cases, Powassan virus can also cause inflammation of the brain (i.e., encephalitis) and membranes surrounding the brain and spinal cord (i.e., meningitis), resulting in other neurological symptoms like confusion, loss of coordination, and difficulty speaking.  

Of note, 1 in 10 individuals with severe Powassan virus infection die, and about 50% of those who survive experience long-term health complications. Some survivors suffer from permanent health issues, including memory problems, persistent headaches, and muscle wasting.  

Treatment of Powassan virus disease includes supportive care to help minimize symptoms, including rest, fluids, and medications such as NSAIDS, steroids, and immunoglobulins. Those with severe forms of Powassan virus infection may require hospitalization for more intensive care, like IV fluids for hydration, medications to decrease brain swelling, and assistance with ventilation and breathing.   

Currently there are no vaccines that prevent Powassan virus infection, so the best way to reduce the risk is through prevention. To prevent tick bites, it is advised to always wear clothing that minimizes exposed skin, like long pants and long-sleeved shirts; avoid tick habitats or areas with lots of vegetation; and use tick repellants when spending time outdoors.