Acute Flaccid Myelitis (AFM)

What is AFM?

Acute flaccid myelitis (AFM) is an uncommon but serious condition that affects the nervous system, specifically the spinal cord. Most patients experience sudden onset of limb (arm and leg) weakness. AFM can be caused by viruses, including enteroviruses. AFM can also be caused by other viruses, including flaviviruses (West Nile virus, Japanese encephalitis virus), herpesviruses, and adenoviruses. Most patients with AFM have a mild respiratory illness or fever before their limbs are affected. Other potential causes of AFM are still being explored.

Who gets AFM?

Anyone of any age can get AFM, but it is more commonly reported in young children.

How is AFM spread?

AFM is not spread from person to person. The viruses that are believed to cause AFM may be contagious from one person to another or may be spread by a mosquito or other vector.

What are the symptoms of AFM?

Most patients will have sudden onset of limb weakness and loss of muscle tone and reflexes. In addition, some patients will experience:

  • facial droop or weakness,
  • difficulty moving the eyes,
  • drooping eyelids, or
  • difficulty with swallowing or slurred speech.

Numbness or tingling is rare in patients with AFM, though some people have pain in their arms or legs. Some patients with AFM may be unable to urinate. The most severe symptom of AFM is respiratory failure, which happens when the muscles involved with breathing become weak. This can require urgent ventilator (breathing machine) support.

How soon after exposure do symptoms appear?

The time between exposure and symptom development depends on the virus causing the illness.

How is AFM diagnosed?

Clinicians diagnose AFM by taking a thorough medical history, doing a physical exam, and performing an MRI to review pictures of the spinal cord. Laboratory tests on biological specimens, including cerebrospinal fluid, blood, and stool, are needed to confirm the virus responsible for illness.

What is the treatment for AFM?

There is no specific treatment for AFM, but a clinician may recommend physical or occupational therapy to help with arm or leg weakness caused by AFM. Physical rehabilitation might improve long-term outcomes if implemented during the initial phase of illness.

How can AFM be prevented?

Many daily healthy habits can help prevent viral infections.

  • Wash hands often with soap and water for at least 20 seconds.
  • Avoid close contact with people who are sick.
  • Cover coughs and sneezes with a tissue or the inside of your elbow, not hands.
  • Clean and disinfect frequently touched surfaces, like toys, mobile devices, and doorknobs.
  • Stay up to date on recommended vaccinations.

How can I get more information about AFM?

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Last Updated: January 6, 2025