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Acute Flaccid Myelitis (AFM)

Florida Health

Disease Control

Acute flaccid myelitis (AFM) is an uncommon but serious neurologic condition that may cause limb weakness and poor muscle response. Individuals of any age may get AFM, but it is most common in young children (more than 90%). AFM can be caused by viruses, including enteroviruses, and most patients have respiratory symptoms consistent with a viral infection within one week prior to limb weakness.

National AFM surveillance began in 2014 with an increase in reports of AFM in the United States. This surveillance has helped identify increases every other year in 2014, 2016 and 2018. This pattern was expected to continue in 2020, but case levels may have been impacted by the COVID-19 response. Surveillance has also shown a seasonal pattern, with most cases developing AFM in late summer or early fall. This time period coincides with increased circulation of many viruses, including enteroviruses.

  • Symptoms and Treatment
  • Transmission and Prevention
  • AFM Occurrence in Florida
  • Resources

Most patients with AFM will have sudden onset of arm or leg weakness and loss of muscle tone and reflexes. Some patients may also experience:

  • Difficulty moving the eyes
  • Drooping eyelids
  • Facial droop or weakness
  • Difficulty swallowing or slurred speech
  • Pain in arms or legs
  • Pain in neck or back

Uncommonly, patients with AFM may experience numbness or tingling in arms or legs. The most severe symptoms of AFM include difficulty breathing due to muscle weakness and serious neurologic complications such as body temperature changes and blood pressure instability.

Symptoms can progress rapidly and be life threatening.  If you see potential symptoms of AFM in your child, contact your health care provider right away.  

AFM can be caused by viruses. Specimens collected from patients with AFM have detected coxsackievirus A16, enterovirus A71 (EV-A71), enterovirus D68 (EV-D68) and antibodies specific to enteroviruses. These viruses generally cause mild illness and it is unclear why a small number of individuals develop AFM after viral infection. All stool specimens from AFM patients that the Centers for Disease Control and Prevention (CDC) have received tested negative for poliovirus. This means that the cases of AFM since 2014 are not caused by poliovirus.

Since AFM can develop after a viral infection, The Florida Department of Health recommends parents and children take basic steps to avoid becoming infected with or spreading a virus including:

  • Staying home when sick
  • Covering coughs and sneezes
  • Avoiding contact with individuals who are sick
  • Frequent hand washing with soap and water for a minimum of 20 seconds
  • Cleaning and disinfecting frequently touched surfaces


Onset Year

Number of Cases*















* Numbers reflect confirmed and probable AFM cases; CDC reports only confirmed cases, so numbers may differ.