Acute Flaccid Myelitis (AFM)


AFM is an illness with onset of acute focal limb weakness and either:

  • a magnetic resonance image (MRI) showing a spinal cord lesion largely restricted to gray matter and spanning one or more spinal segments,
  • or cerebrospinal fluid with elevated white blood cell count.

Most patients with AFM will have sudden onset of limb weakness and loss of muscle tone and reflexes. In addition to the limb weakness, some may also experience one or more of the following symptoms:

  • facial droop or weakness
  • difficulty moving the eyes, drooping eyelids
  • difficulty with swallowing or slurred speech
  • some patients may be unable to pass urine

Some patients with AFM experience pain in their arms or legs, though numbness or tingling is rare.

The most severe of the symptoms that can sometimes be associated with AFM is respiratory failure which can occur when the muscles involved with breathing become weak. This can require ventilator support.

Please note: All patients with no sensory or cognitive loss that present with a syndrome meeting the clinical criteria for AFM also meet the criteria for consideration as a possible paralytic poliomyelitis case and so can be considered 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 Acute Flaccid Myelitis (AFM) 
  • To help identify causes of AFM in the United States.
  • To prevent transmission of AFM.
  • 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)