Acute flaccid myelitis: What parents need to know

Photo of a toddler's feet

If you’re a parent, chances are you’ve heard the recent news reports about acute flaccid myelitis, or AFM. So far this year, 106 cases of AFM have been confirmed in 26 states, including two in Massachusetts. Similar outbreaks occurred in 2014 and 2016.

AFM is a rare but serious condition that causes polio-like symptoms, mostly in children. It’s also a bit of a mystery. Researchers and clinicians are still trying to learn more about exactly what causes this illness and how it might be prevented. We spoke with Dr. Leslie Benson, a neurologist at Boston Children’s Hospital, to provide an update on the latest information on AFM.

What is acute flaccid myelitis?

AFM is most likely a viral infection that affects the spinal cord or parts of the brainstem. It can cause sudden weakness and paralysis, ranging from weakness of the facial muscles to limb weakness to weakened breathing. It often starts during or just after a mild respiratory illness or fever. People describe AFM as ‘polio-like’ because, like polio, it’s a viral infection of the motor nerves in the spinal cord.

What causes this condition?

It appears to be linked to several fairly common viruses, including enterovirus D68, enterovirus A71 and others.

We don’t yet know why some people with these viruses develop AFM while most don’t. A group of researchers are currently doing genetic testing in those who have developed AFM and their family members to see if there’s something in certain people’s genes that makes them predisposed to AFM.

Who gets AFM?

Most cases are in children, particularly in younger kids. This year the average age is 4 years, though it’s possible in children of any age and adults.

What are the symptoms of AFM?

The early signs of AFM include inability to move one of the limbs or the face or pain in the weak limb, neck or back. If your child has any of these symptoms, it makes sense to have them checked out by their primary care physician. Although it’s a scary illness for parents to think about, it’s important to remember that it’s very rare.

Is there any way to prevent AFM?

Because we’re still learning more about AFM, the only prevention tool we know of right now is good infection control. This means taking the same precautions you would to avoid colds and the flu, such as coughing into your elbow, washing your hands often and avoiding close contact with those who are sick.

Will there be more cases this year?

Although we can’t say for certain, we’re hoping this cluster of AFM is coming to a close for the season and we won’t see any more new cases. Now it’s a matter of sorting out the data to learn more. There’s a lot of effort being put forward in trying to learn more about this condition. The Centers for Disease Control (CDC) has stepped up efforts after this year’s outbreak, and a national working group of clinicians from across many specialties are also coming together to try to figure this out.

Headshot of Dr. Leslie BensonAbout our expert: Leslie Benson, MD, is an assistant in the Department of Neurology and assistant director of the Pediatric Multiple Sclerosis and Related Disorders Program and Pediatric Neuro-Immunology Program at Boston Children’s and an instructor of neurology at Harvard Medical School.