by Stephanie Eckelkamp
Lyme disease is the most prevalent tick-borne disease in the U.S. and rightfully gets the most attention. But you may have noticed recent headlines about another disabling and potentially deadly infection transmitted via tick bites — Powassan virus (POWV). While still quite rare, cases of POWV have been on the rise in parts of North America and Europe.
POWV can attack the nervous system and has been known to infect the brain. Although some infected individuals may have no symptoms and remain healthy, others may experience encephalitis or meningitis (inflammation of the brain or the membranes surrounding the brain and spinal cord), long-term neurological disabilities, and even death. Particularly troubling is the fact that POWV has no established treatment protocol.
Needless to say, it’s not something you want. But don’t panic just yet. Arming yourself with the facts about POWV can help you take precautions to prevent an infection altogether or identify symptoms earlier so you can seek swift medical attention. Let’s take a look below.
An Overview of the Powassan Virus
POWV got its name from Powassan, Ontario, where it was first identified by researchers in 1958, after performing the autopsy of a young boy who died of severe encephalitis. Among people who experience this severe, neuro-invasive form of POWV, approximately 1 in 10 die. Of those who survive, around 50% experience long-term neurological disability, from memory problems to muscle wasting to recurrent headaches.
Three types of ticks commonly found in the Eastern half of the United States are known to spread POWV — Ixodes cookei (groundhog tick), Ixodes marxi (squirrel tick), and Ixodes scapularis (blacklegged or deer tick). But of these ticks, only deer ticks regularly bite and infect humans. As you may know, deer ticks also transmit Lyme disease and a variety of other tick-borne coinfections to humans. Typically, rodents and small mammals such as mice, groundhogs, and squirrels serve as reservoirs for POWV; then, after ticks feed on these infected hosts, they pass the virus on to the next animal or human they bite.
There have only been a few hundred human cases of the virus since 1958, but records show a 300% increase in incidence over the past 16 years or so. Why, exactly? Opinions vary, but some experts believe it’s due to a change in the ticks that carry it. “There has been an important change in the ecology of Powassan virus in that the deer tick has recently become infected with the virus,” according to Durland Fish, PhD, a former professor of epidemiology at the Yale School of Public Health. “Until a few decades ago, it was only transmitted by a tick species that does not commonly bite humans and human cases were extremely rare.”
Another reason for the apparent uptick could simply be an increase in surveillance and diagnosis. “Lots of people have gotten sick over the years without a known cause,” says Dr. Rawls, MD, Medical Director of RawlsMD and Vital Plan. “If you weren’t even looking for something 20 or 40 years ago, and then you start testing and finding cases, it’s not that it’s necessarily new or emerging — it’s just that we’ve started recognizing it. All of these tick-borne microbes have likely been around for a long, long time.”
Where is the Powassan Virus Found?
Human cases of POWV are primarily found where deer ticks are located. In the U.S., most cases have been identified in Northeastern states as well as the Upper Midwest or Great Lakes region — similar to the distribution of Lyme disease.
Between 2011 and 2020, a total of 194 cases of POWV were reported in 13 states, with most cases occurring in late spring, early summer, and mid-fall, when ticks are most active. Here’s the breakdown:
- Massachusetts – 38 cases
- Minnesota – 38 cases
- Wisconsin – 36 cases
- New York – 27 cases
- New Jersey – 13 cases
- Connecticut – 10 cases
- Pennsylvania – 10 cases
- Maine – 9 cases
- New Hampshire – 5 cases
- Rhode Island – 4 cases
- North Dakota – 2 cases
- Indiana – 1 case
- North Carolina – 1 case
Want to know about any recently documented cases near you? Call your local health department. Because POWV is considered a “nationally notifiable condition,” all known cases must be reported to local public health authorities.
Symptoms of the Powassan Virus
POWV transmission may occur in as little as 15 minutes of being bitten by an infected tick. After infection, there’s typically an incubation period of one to five weeks before symptoms emerge. Some people infected with the virus may never develop symptoms, but for those who do, they tend to begin with the following flu-like symptoms:
Days to weeks after these initial symptoms, a subset of people will go on to experience more severe neurological effects, such as encephalitis and meningitis. “The types of cells this virus prefers to infect are neurological, so it can really wreak havoc and have devastating consequences,” says Dr. Rawls. At this stage, people may experience:
- Loss of coordination
- Difficulty speaking
- Death (in about 1 in 10 people with severe illness)
Is There Any Way To Diagnose and Treat Powassan Virus?
POWV may not always be promptly diagnosed because it’s quite uncommon — thus, it’s not top of mind for most health care providers. Plus, “mild symptoms easily mimic other viral and tick-borne infections,” says Dr. Rawls. This is why just being aware of the tick-borne virus and how it manifests may give you an edge.
If you’re experiencing any of the initial symptoms above and have recently had a tick bite (or you’ve spent time in nature — gardening, hiking, doing yard work, etc.), contact your doctor and provide them with as much information as possible. If you’re experiencing any of the severe symptoms above, call 911 immediately.
Your doctor should perform a physical exam and ask you a range of questions about your recent outdoor activities and travels that may have put you in close proximity to deer ticks or whether you’ve recently had a blood transfusion. With this information, your doctor can make a preliminary diagnosis, which may be confirmed by testing the blood or the cerebrospinal fluid for POWV-specific antibodies. Testing for other tick-borne infections is important, too, as these should be treated simultaneously to improve your odds of recovery.
If your symptoms don’t stop on their own, you will likely be hospitalized. While there’s no established treatment protocol known to resolve the tick-borne viral infection, patients often receive fluids to stay hydrated, respiratory support, and drugs to help reduce swelling in the brain, which may include high-dose corticosteroids or intravenous immunoglobulin (IVIG).
Unfortunately, once symptoms become severe, chances of death and permanent neurological disability significantly increase.
How to Prevent Powassan Virus
As they say, prevention is the best medicine — and this is particularly true for POWV, given its high virulence (i.e., its ability to cause severe illness) and lack of treatments. “Virulence is a function of whether or not our immune system recognizes something, whether we have built-in immunity to it,” says Dr. Rawls. “We have a level of natural immunity to many tick-borne infections, but not Powassan virus, probably because it’s been a lot less common.”
Your absolute best bet is to avoid a tick bite altogether. Wear protective clothing when out in nature and shower afterward, avoid brushy areas and stay on the trail when hiking, perform regular tick checks on you and your pets, and use an effective tick repellent featuring essential oils like oil of lemon eucalyptus or insecticides such as DEET, picaridin, or permethrin. If you do get bitten, remove the tick promptly and carefully, following the steps in this article.
Currently, there is no vaccine for POWV. Scientists have recently begun designing and testing various types of vaccines (e.g., DNA vaccines, VLP vaccines) against the virus on animals, but it’s unclear when or even if these vaccines will be available for humans.
POWV is a rare but virulent tick-borne pathogen for which humans have no natural immunity. While some people infected with this virus will remain asymptomatic, others will go on to develop flu-like symptoms followed by more serious neurological side effects such as encephalitis and meningitis that may result in permanent disability or death.
Because there’s no vaccine or cure for POWV, remaining tick-ready is critical. Be sure to take the appropriate preventative measures whenever you’re outdoors, particularly in areas known for ticks. Additionally, consuming such phytochemical-rich herbs as Japanese knotweed, cat’s claw, andrographis, Chinese skullcap, reishi, cordyceps, and garlic to bolster your body’s defenses may offer an extra layer of protection to augment your overall health both before or after you’ve gotten a tick bite, says Dr. Rawls.
Finally, prioritize basic healthy lifestyle habits — think: getting plenty of sleep, keeping stress low, exercising, reducing your exposure to environmental toxins, and eating a nutritious diet. These everyday practices support your health on a cellular level so that you’re better equipped to neutralize any threat — when or if it comes.
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