Acute Flaccid Myelitis (AFM)

Please see the attached document for information regarding acute flaccid myelitis, a serious condition that causes weakness in the arms or legs.

Key Points – Acute Flaccid Myelitis

What We Know
Since 2014, CDC has learned the following about the AFM cases:

Most patients are children.

• The patients’ symptoms have been most similar to complications of infection with certain viruses, including poliovirus, non-polio enteroviruses, adenoviruses, and West Nile virus.
• All of the AFM cases have tested negative for poliovirus.
• Enteroviruses most commonly cause mild illness. They can also cause neurologic illness, such as meningitis, encephalitis, and AFM, but these are rare.
• CDC has tested many different specimens from AFM patients for a wide range of pathogens (germs) that can cause AFM. To date, no pathogen (germ) has been consistently detected in the patients’ spinal fluid; a pathogen detected in the spinal fluid would be good evidence to indicate the cause of AFM since this condition affects the spinal cord.
• The increase in AFM cases in 2014 coincided with a national outbreak of severe respiratory illness among people caused by enterovirus D68 (EV-D68). Among the people confirmed with AFM, CDCdid not consistently detect EV-D68 in every patient. During 2015, CDC did not receive information about large EV-D68 outbreaks in the United States, and laboratories reported only limited EV-D68 detections to CDC’s National Enterovirus Surveillance System (NESS). During 2016, CDC was informed of a few localized clusters in the United States. Learn more about EV-D68.

What We Don’t Know
Among the people who were diagnosed with AFM since August 2014:

• The cause of most of the AFM cases remains unknown.
• We don’t know what caused the increase in AFM cases starting in 2014.
• We have not yet determined who is at higher risk for developing AFM, or the reasons why they may be at higher risk.
• We do not yet know the long-term effects of AFM. We know that some patients diagnosed with AFM have recovered quickly, and some continue to have paralysis and require ongoing care.

More information:

• AFM website: www.cdc.gov/acute-flaccid-myelitis/index.html
• AFM Investigation page: www.cdc.gov/acute-flaccid-myelitis/afm-surveillance.html
• For Clinicians and Health Departments: www.cdc.gov/acute-flaccid-myelitis/hcp/index.html