It’s mysterious, it’s dangerous and it’s got parents on edge from coast to coast.

It’s a medical condition called acute flaccid myelitis, or AFM. The disease causes sudden, unexplained paralysis, usually in children. Its resemblance to polio has caused the public to take notice.

Federal health officials have confirmed 62 cases of AFM in the U.S. this year, and 65 more are under investigation. There are four suspected cases in California, according to the state’s Department of Public Health.


Her toddler suddenly paralyzed, mother tries to solve a vexing medical mystery »

This is the third time the nation has seen a nationwide uptick in AFM; so far, 2018 appears to be following the pattern seen in 2014 and 2016. Here’s a look at what experts know — and don’t know — about the condition.

What is AFM?

Acute flaccid myelitis is a condition that affects the spinal cord, making it difficult for people to move their limbs. The paralysis it causes typically comes on suddenly, and it can be permanent.


More than 90% of cases are in children.

Is this a new disease?

No, but doctors only began noticing it in 2014. That’s when dozens of children began showing up in hospitals unable to move their arms or legs.

Ultimately, 120 children were diagnosed with AFM that year. There was another burst of cases in 2016, and we’re in the midst of a third one now.

What causes AFM?

Scientists would love to know.


Some experts believe that it is linked to a biennial summer virus, because cases tend to peak in the late summer and early fall in alternating years.

“Despite all of our efforts, we haven’t been able to identify the cause of this mystery illness,” Dr. Nancy Meissonier, director of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases, said this week.

How is it different than polio?

Though AFM’s symptoms resemble polio, no AFM patients have tested positive for poliovirus.


Some patients diagnosed with AFM were found to have enterovirus D68, a cousin of poliovirus, in their systems. CDC officials have not confirmed that enterovirus D68 causes AFM. They say they are investigating several potential causes, including environmental toxins.

How common is it?

Not common at all. There have been 386 cases in the United States since 2014. That works out to a rate of less than 1 in a million, according to Meissonier.

“As a parent myself, I understand what it’s like to be scared for your child,” Meissonier said. “Parents need to know that AFM is very rare, even with the increase in cases we’re seeing now.”

How do you get it?

Without knowing what’s causing the condition, it’s hard to say. Doctors are unsure who is at risk and why.


Are certain people more vulnerable than others?

Children seem to face a higher risk than adults. The average age of patients diagnosed with AFM since January is 4.

Cases of AFM have been confirmed in 22 states across the U.S.

Is there anything I can do to protect myself?

Doctors recommend washing your hands, staying up to date on your vaccinations and using insect repellent to ward off mosquito bites.

Meissonier also said that anyone experiencing sudden muscle weakness should seek immediate medical attention.