Recent news articles have reported on an alarming and dangerous disease carried by ticks that may be on the increase. The disease is caused by the Powassan virus, which can infect the nervous system and leave people with permanent brain damage. The reports are scary but how worried should we be?
What is Powassan virus?
Powassan virus is related to the more common West Nile virus, but unlike West Nile virus, which is transmitted by mosquitoes, Powassan virus is transmitted by the bite of an infected tick, most often the deer tick, the same one that transmits Lyme disease. In Lyme disease, ticks need to be attached for 24 to 48 hours to transmit the disease. However, Powassan virus can be transmitted more quickly, within about 15 minutes after the tick attaches.
In the United States, Powassan virus infections have been reported in the Northeast, mainly in the Hudson River valley, and in the Great Lakes region.
What are the symptoms of Powassan virus infection?
News reports focus on very severe cases, ones that involve serious brain infection (meningoencephalitis). Severely affected people have symptoms related to the nervous system, including headache, weakness, confusion, and seizures. About 10% die, and half have long-term neurologic problems such as memory loss and frequent headaches.
However, it is important to remember that most people who have Powassan virus infection have only a minor flu-like illness and often don’t even see a doctor. People with severe brain infections make up only a very small number of people infected with Powassan virus.
So should I worry?
Not really. Although Powassan virus infection can be severe and even fatal, the Centers for Disease Control and Prevention has reported only 75 cases of severe brain infection due to Powassan virus over the last 10 years—most recently about 6 to 12 cases per year. So even if you spend a lot of time outdoors and live in or visit an area where Powassan virus or deer ticks are common, you probably do not have to worry too much.
There is no vaccine to prevent Powassan virus infection.