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What Is Acute Flaccid Myelitis?

Acute flaccid myelitis (AFM) is a rare condition that affects the spinal cord. It comes on suddenly and makes muscles weak and floppy. It looks similar to polio, so it is sometimes called a “polio-like” illness. It is most commonly seen in children around age 6.

What Are the Signs & Symptoms of Acute Flaccid Myelitis?

Acute flaccid myelitis (mye-uh-LYE-tiss) often happens after a respiratory infection, such as a cold.

A child with AFM usually has sudden weakness in the arms and legs. Other signs of acute flaccid myelitis include:

  • arm, leg, or neck pain
  • drooping eyelids
  • trouble moving the eyes
  • drooping mouth
  • slurred speech
  • trouble swallowing
  • trouble breathing

If you or your child have any of these symptoms, get medical care right away.

What Causes Acute Flaccid Myelitis?

Experts think that AFM is caused by certain types of viruses, such as enterovirus D68.

AFM is not a new problem, but many people are learning about it now because of recent outbreaks. An outbreak is when a disease happens in greater numbers than expected in a particular area. In the United States, outbreaks of AFM seem to happen every couple of years, alongside an increase in some types of viral infections. But it's still very rare.

What Might Help Prevent AFM?

It isn’t clear why some children get AFM after a viral infection and others don’t. So it’s best if everyone tries to avoid spreading germs by:

  • washing hands well and often
  • keeping vaccinations up to date
  • staying away from people who are sick
  • keeping household surfaces clean and disinfected
  • keeping sick children home from school and daycare

For more information about acute flaccid myelitis, visit the CDC's AFM page.

Medically reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: September 2022