Ticks don’t just carry Lyme disease. What you should know about Powassan virus

Click to play video: 'Watch out for these 5 tick-borne diseases'
Watch out for these 5 tick-borne diseases
With the warmer weather upon us, ticks have come out of hibernation. Here are some of the diseases to look out for – May 4, 2018

As the weather gets warmer and people spend more time outdoors, public health authorities are warning people to watch for ticks. These little bugs can potentially carry more than just Lyme disease.

The United States Centers for Disease Control and Prevention says that the number of reported cases of Powassan virus has been increasing recently. Although it’s very rare, this virus can have potentially fatal consequences.

Here’s what you need to know about Powassan virus.

What is it?

Powassan virus is named after the town of Powassan, Ont., where the first case was reported in the 1950s.

It’s a virus that’s transmitted by ticks. “In most people who are infected there are no symptoms or it may be mild flu-like symptoms,” said Dr. Nick Ogden, who works in the National Microbiology Laboratory of the Public Health Agency of Canada.

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However, in some cases, it can infect the nervous system, potentially causing encephalitis – a swelling in the brain – or other brain damage. About one in 10 of these people will die as a result, he said, “and a reasonable number of people who survive will go on to suffer long-lasting neurological problems.”

How common is it?

It’s rare, said Ogden.

“It’s a very rare pathogen,” agreed Dr. Mark Nelder, an entomologist with Public Health Ontario. “It’s very rarely seen in Canada. We’ve seen about 20 cases since 1958.”

Part of the reason is that many of the ticks that carry this virus live in the nests or burrows of squirrels and groundhogs. “We don’t come into contact with those ticks unless we’re digging in the garden and have to dig up the nests of these mammals,” said Ogden.

But, one variant of the virus can be found in the more common black-legged tick, the same one that carries Lyme disease. It’s found above ground, which means it’s more likely to bite people. However, only a tiny proportion of ticks carry Powassan virus, said Ogden.

In the U.S., 21 cases were reported in 2016, mostly in the northeast and Great Lakes region, bordering Canada. It is becoming more common there though, which means that Canadian public health authorities are watching.

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Powassan virus neuroinvasive disease cases reported by state of residence, 2007–2016
Powassan virus neuroinvasive disease cases reported by state of residence, 2007–2016. Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention

“It’s definitely on our radar and there is concern wherever people are exposed to ticks for sure,” said Nelder.

“The ticks have only come into (Ontario) in the last 10 years mostly. They’ve been growing in numbers. So it’s a matter of time before the other pathogens start to appear.”

How do you protect yourself?

The best way to prevent Powassan virus is the same as preventing Lyme disease: try not to get bitten.

You should avoid walking in brushy, wooded areas, said Nelder. And if you do, stick to the trail, wear long sleeves and tuck your pants into your socks to stop ticks from getting on your skin.

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When you get home after walking in a potentially tick-infested area, it’s a good idea to wash your clothes and put them in the dryer on high heat to kill any remaining bugs, he said. Showering or bathing can wash off any ticks that were crawling on your skin, and you should check yourself carefully for any that have latched on and remove them.

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