Acute Flaccid Myelitis (AFM)

In addition to the limb weakness, some people may also experience one or more of the following symptoms: 

  • gait difficulty
  • facial droop or weakness 
  • difficulty moving the eyes
  • drooping eyelids 
  • difficulty talking or swallowing
  • unable to pass urine 
  • pain in arms, legs, and/or neck 
  • numbness or tingling 

The clinical presentation is similar to poliomyelitis, but the polio virus has not been detected in any specimens from patients with AFM.

AFM is considered a medical emergency as some patients can experience rapid respiratory failure and may require ventilator support.

Cause: There is no single known cause of AFM; all infectious and non-infectious etiologies are investigated. It has been primarily associated with viruses such as non-­polio enteroviruses which typically cause mild illness such as a fever or respiratory infections. Other viruses, including flaviviruses, herpesviruses, and adenoviruses, are considered.

AFM can also resemble other conditions, including transverse myelitis and Guillain-Barré syndrome. For most reported cases across the US, the cause has not been identified. More research needs to be done to better understand why some people develop AFM after a viral infection and why others do not. Providers should consider a diagnosis of AFM in late summer or early fall, especially in patients with preceding viral symptoms.

Illness and Treatment: AFM is treated through supportive care, which is recommended by teams of expert health care providers on a case-by-case basis. The long-term effects of AFM are different for each person. Some people diagnosed with AFM recover quickly and completely. Others have continued weakness and require ongoing, high-level care.

Additional Risks: AFM appears to affect children more than adults. About 90% of acute flaccid myelitis cases affect children between the ages of 1 and 7.

Please note: All patients meeting the clinical criteria for AFM also meet the criteria for consideration as a possible paralytic poliomyelitis case, which is immediately notifiable to local health jurisdictions in Washington under WAC 246-101. Travel and immunization histories should be obtained as soon as possible on all suspected AFM cases to help rule out polio as a possible cause. 

Purpose of Reporting and Surveillance

  • To identify cases of AFM and establish an incidence baseline and burden of the condition in Washington State. 
  • To help identify causes of AFM in the United States.
  • To understand the impact of AFM among all age groups.

Legal Reporting Requirements

  • Heath care providers and Health care facilities: notifiable to local health jurisdiction within 24 hours
  • Laboratories: no requirements for reporting
  • Local health jurisdictions: notifiable to the Washington Department of Health (DOH) Office of Communicable Disease Epidemiology (CDE) within 7 days of case investigation completion or summary information required within 21 days. (1-206-418-5500 or 1-877-539-4344)