Powassan virus cases are rising. Why is ‘Lyme disease’s deadly cousin’ so concerning?

 Ixodes scapularis or “the black-legged tick” carries the Powassan virus
Ixodes scapularis or “the black-legged tick” carries the Powassan virus Copyright AP Photo
Copyright AP Photo
By Sarah Palmer
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Dubbed “Lyme disease’s deadly cousin,” the Powassan virus has been the subject of a recent study by Yale School of Public Health - and cases are increasing.


Named after a town in Ontario where it was first discovered in the 1950s, the reported number of Powassan virus cases have been increasing across the US and Canada.

Researchconducted by the Yale School of Public Health has uncovered that there’s a high concentration of cases in New York State, Maine and Connecticut especially.

But what is Powassan virus - dubbed “Lyme disease’s deadly cousin” - and is it really becoming more common?

What is the Powassan virus?

Much like its cousin Lyme disease, the Powassan virus is passed on through tick bites. It’s predominantly passed on by deer and groundhog ticks, otherwise known as ixodes scapularis or “the black-legged tick”.

One of the main concerns with the Powassan virus in comparison to Lyme disease is the rapidity with which it can infect people.

While the transmission period between a tick bite and humans contracting Lyme disease can take as long as two to three days, Powassan can take hold within just 15 minutes though symptoms often don’t show until a week to - four weeks later.

What are the symptoms of Powassan virus?

The virus is actually rarely diagnosed because the majority of people with it are asymptomatic.

But for those who do show symptoms, they can be severe.

Ranging from fever, chills, fatigue, nausea and stiffness, the virus can also cause seizures and memory loss and, in a small number of cases, it can be life-threatening.

Why is Yale looking into it now?

The most recent research into the virus, conducted by Yale School of Public Health, started in 2008 and concluded in 2019.

Chantal Vogels is a research scientist in the Department of Epidemiology of Microbial Diseases at the Yale School of Public Health and a co-author of the study.

In the recently published results, she explains how there was very little genomic information about Powassan virus until this latest study.

“We were able to explore patterns of transmission and spread and unravel the ecology of the virus,” she said. "It's incredibly important to do surveillance to know what's out there".

What were the results of the research?

The key finding from the study was that the virus is largely concentrated in very specific areas.

According to the report, “the virus now appears to be moving slowly or staying put, simmering in specific hotspots, and evolving independently in each one.

“For instance, the scientists could find no evidence that separate clades of the virus were mingling with each other across a 20-kilometre stretch”.

It was also noted that there has, in recent years, been an increase in diagnoses.

From the very first case in 1958 through to around 2006, just one case per year was detected. But since the early 2010s, “dozens of diagnoses have been made nearly every year,” according to the study.


The increase in cases isn’t necessarily something to worry about, though.

Powassan virus is still very much considered a “rare” disease and the increase in cases is put down to medical professionals being more inclined to check for Powassan if the symptoms are present.

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