A runny nose or cough are normal symptoms during the fall, but this year doctors in the United States and Canada are reporting an escalation of symptoms among a small but notable number of kids. One day children have a cold, and the next they’re experiencing polio-like paralysis. It’s not the first time this has happened, either.

The condition is called Acute Flaccid Myelitis, or AFM, and it’s a rare disorder that impacts a person’s nervous system. Over the last couple of months, a rise in AFM cases among kids has puzzled doctors. The U.S. Centers for Disease Control and Prevention (CDC) says that there have been 219 cases reported in 2018 thus far, and 80 cases confirmed in the U.S. The Public Health Agency of Canada reported that there were a combined 44 cases under investigation or confirmed. Currently, 90 percent of the people affected are children under the age of 18.

Clusters of these symptoms appear around flu season. In the fall of both 2014 and 2016, there were similar reports of these inexplicable cases. While there are several theories about the cause, much remains unknown about AFM.

“The problem with this condition is [that] to some extent there’s more questions than answers,” says Dr. Jeremy Friedman, an associate pediatrician-in-chief at The Hospital for Sick Children in Toronto, who is treating several children with the mysterious paralysis. “In this particular cluster, we’re talking about a dozen cases in a condition which we normally see a few times a year.”

Here’s everything you should know.

What is causing the outbreaks?

This is the hardest question to answer. The ambiguous nature of AFM comes from the lack of evidence to explain its cause. The periodical nature of the illness offers some clues, according to Friedman. The virus has historically spiked in the late summer and early fall. Right now, doctors are homing in on a group of viruses called enteroviruses.

“The problem with this condition is [that] to some extent there’s more questions than answers.”

In previous cases, doctors combatting clusters of AFM in 2014 and 2106 have suspected a strain of enterovirus called D68. Enteroviruses are in the same family as polioviruses, and have no vaccine or specific treatment. This means that patients need to wait out the course of the disease.

This year, the link is not as clear, says Friedman. “We have seen a few [people] test positive for enterovirus, but only one has tested positive for enterovirus D68,” he says. “That particular strain of enterovirus does not seem to be as big a feature as it perhaps was in 2014.”

Also stymieing the search for a solution is the unprecedented nature of the disease. Friedman believes a viral cause is still a strong theory, but more research is needed.

What are the symptoms?

The disease affects the body’s nervous system through damage to the spinal cord. Coinciding inflammation in different regions of the spinal cord causes a range of paralysis-related symptoms. “Depending on what part of the spinal cord is affected, you might see an arm that’s paralyzed, you might see a leg that’s paralyzed, and you might see both legs,” says Friedman.

Doctors have been able to isolate viruses in the noses of the sick children, but have not actually been able to find evidence of enterovirus in the spinal fluid of affected patients. According to Friedman, this could be a sign that children’s immune systems could be to blame for some of the symptoms they’re experiencing.

“It makes it seem a bit more likely that it’s not the virus infection that’s causing the symptoms per se, but it’s more related to the body’s immune response, that’s triggered by the viral infection, that might be causing the symptoms,” he says.

What are the treatment options?

There’s currently no cure for AFM, but doctors can alleviate its symptoms. Treatment strategies are different based on what a person is experiencing. Currently, doctors use physical therapy in combination with intravenous anti-inflammatory medication to reduce the damage on the spinal cord. But Friedman told Medium that some children still need other, “more sophisticated” treatments to try and help with immune response.

While some children appear to be improving more rapidly than in previous years’ outbreaks, some will require more intensive treatments. With our current understanding of AFM, predicting individual outcomes has proven to be very challenging.

“I think that when one counsels families, one has to be really honest and transparent about the fact that there really isn’t enough experience with this condition to accurately predict how each individual case is going to play out,” Friedman says.

What’s the prognosis for affected children?

Most of the kids currently affected by AFM have begun to recover or are already recovered, with a few exceptions, says Friedman. Since the initial news of the Toronto outbreak in October, the number of cases has not grown dramatically.

“I would say that I think the cluster of cases that we’ve seen at SickKids seems to have slowed down,” Friedman says. “And really, we haven’t seen a lot of activity over the last week at all.”

But there is still work to do. The CDC and Public Health Agency of Canada will continue to investigate the epidemiological aspects of the illness — or the larger picture details of how the disease is transmitted in a community. There are also coordinated efforts by doctors and researchers who are treating the disease on the front lines. “There is, in Canada, a group of pediatric neurologists that are sharing all the cases that are being seen across Canada, to pool whatever information they have to try and sort of maximize the learning that can be extracted from this experience,” Friedman says.

The best ways to reduce the risk of AFM are still under investigation, but the CDC recommends that people wash their hands frequently, as it’s one of the best ways to avoid getting sick and spreading disease.