What we know about the rise of the polio-like condition acute flaccid myelitis

In recent days, news about a sudden rise in a polio-like illness, called acute flaccid myelitis, among children in Canada and the US has been striking fear in parents. We asked Jeremy Friedman, associate paediatrician-in-chief at SickKids Hospital, where many of the cases are being treated, what we know so far and how parents can keep their kids safe.

What is acute flaccid myelitis?

Acute flaccid myelitis (AFM) is a rare condition that affects the nervous system, making muscles in the arms and legs weak. It typically affects children under the age of 15, and it appears after a child has contracted a virus, which can cause symptoms of the common cold. Some children develop weakness in an arm or leg, usually on one side of the body, while others will experience permanent paralyzation in their limbs, which is why some people are comparing it to polio. 

"A big part of acute flaccid myelitis is sudden weakness and paralysis of a limb," says Friedman. "And it is quite similar to polio in that respect."

But, Friedman notes, there is a big spectrum of severity, and treatment varies on a case-by-case basis. While some of the kids being treated at SickKids have shown signs of improvement, others have shown none. A few have been out of the hospital in a week or so, while others have been much more sick and could spend weeks in the hospital.

How many kids have been affected by AFM?

While no exact numbers have been released, Friedman says, from what he's heard, there are about 25 cases across Canada. In the US, meanwhile, more than 150 cases are being investigated. So far, about a dozen cases have been confirmed at SickKids in Toronto, and a couple more cases are still being investigated. Overall, the illness is still extremely rare but, given that Friedman says there are generally only about five to 13 cases across the country in an entire year, it's unusual to have so many. Still, he assures, "Even with this cluster of cases, it is a really rare disease."

What causes acute flaccid myelitis?

No one's entirely certain what causes AFM, but there appears to be an association between enterovirus (which is a virus similar to the common cold) and the illness. During a previous rise in cases of AFM, a third of kids tested positive for a certain strain of enterovirus, but, Friedman explains, since not all children with AFM had that enterovirus, and since many kids who contracted that enterovirus never got AFM, there's clearly more to the story.

This year, SickKids reports that some kids have tested positive for enterovirus. But there are certainly other factors at play. In order to get AFM, says Friedman, "You probably need to get the acute infection in a child who has some underlying genetic predisposition to this condition."

Should we worry that cases will continue to rise?

This isn't the first time there's been a rise in cases of AFM. Back in 2014, Friedman says there was a similar cluster of cases around the same time of year. That year, there were 25 cases across Canada, many of which have been linked to a specific virus: enterovirus D68.

"If it behaves the same as it did in 2014, we would expect that, toward the end of the month [October], we would pretty much be getting out of it," says Friedman. But it's difficult to know for sure when the cases are going to taper off.

What can parents do to keep their kids safe?

Since it's a common virus that triggers the illness, it's important to follow all the standard advice for cold prevention, like ensuring kids wash their hands often and teaching them to cough or sneeze into their elbow instead of their hands.

If your child shows sign of a virus—with the typical symptoms of coughing, sneezing, or developing a fever or headache—and suddenly complains of either weakness or a complete loss of function in an arm or a leg, get them to a healthcare provider immediately.

But rest assured that, even when children do pick up a virus, the vast majority will be just fine and won't go on to develop AFM. "This is a really rare condition," says Friedman. "Obviously, this doesn't help the dozen families that are in hospital at the moment, but for most parents, it's still going to be highly unlikely."

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