Cause: The exact cause and the mechanisms by which it damages the nervous system are still unknown. Researchers are investigating both infectious and non-infectious factors that may contribute to this condition. AFM has been primarily linked to viruses, specifically non-polio enteroviruses such as enterovirus D68 (EV-D68) and enterovirus A71, which have been strongly associated with past outbreaks of AFM. Other types of viruses, including flaviviruses, herpesviruses, and adenoviruses, are also considered potential causes.
Illness and treatment: Acute flaccid myelitis (AFM) is a rare but serious neurological condition, characterized by a sudden onset of flaccid weakness in one or more limbs, accompanied by distinct abnormalities in the gray matter of the spinal cord as seen on magnetic resonance imaging (MRI).
In addition to 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 can mimic other conditions, such as transverse myelitis or Guillain-Barré syndrome, making diagnosis difficult. In most reported cases across the United States, the underlying cause remains unidentified.
AFM is managed through supportive care provided by teams of expert healthcare specialists, including neurologists, infection preventionists, and physical and occupational therapists, each selected based on individual needs. Some individuals diagnosed with AFM recover quickly and completely, while others may experience ongoing weakness and require continuous, high-level care. The long-term effects of AFM vary from person to person. Further research is necessary to understand why some individuals develop AFM while others do not.
Sources: unknown
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. AFM is considered a medical emergency as some patients can experience rapid respiratory failure and may require ventilator support. Healthcare providers should consider AFM when patients present with acute sudden muscle weakness especially when preceded by viral symptoms, particularly in the late summer and early fall, when AFM is most common.
Prevention: There is no identified action to take to prevent AFM but preventing viral infections can help reduce the risk of contracting disease.
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).