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Posted on: October 11, 2022

Health Advisory: Acute Flaccid Myelitis


October 6, 2022

Since the end of August 2022, CDC sentinel surveillance sites for respiratory pathogens have been reporting increases in enterovirus D-68 (EV-D68) respiratory disease. EV-D68 is also the main enterovirus responsible for cases of acute flaccid myelitis (AFM) during years when we see increases in AFM cases. AFM is a rare outcome of EV-D68 infection and is a serious neurologic condition that affects mostly children. It typically presents with sudden limb weakness that can lead to permanent paralysis. Traditionally, increases in EV-D68 respiratory disease have preceded cases of AFM by about 2 weeks. Therefore, increased vigilance for AFM is important.
Clinicians should strongly consider the diagnosis of AFM in patients with acute onset of flaccid weakness, especially during August–November, to ensure prompt hospitalization and referral to specialty care. Recent respiratory illness or fever and the presence of neck or back pain or any neurologic symptom should heighten suspicion for AFM. Clinicians should also report possible cases of AFM to Snohomish Health District as soon as they suspect AFM. Case reporting will help states and CDC monitor AFM and better understand factors associated with this illness.
 With the identification of a paralytic polio case in an unvaccinated person in New York in July 2022, healthcare providers should also consider polio in the differential diagnosis of patients with sudden onset of limb weakness, as polio and AFM are clinically similar. Clinicians should obtain stool samples from all patients with suspected AFM to rule out poliovirus infection, especially if the patient is under-vaccinated and has had recent international travel to places where poliovirus is circulating.
 From January 1, 2022, through September 6, 2022, CDC has received 35 reports of suspected acute flaccid myelitis (AFM) in persons from 17 U.S. states; 13 have been classified as confirmed cases of AFM, 2 as probable, 6 as not cases, 1 as suspect, and 13 are waiting information or classification.


In response to a possible increase in cases of AFM, CDC recommends the following:

  • THINK AFM: Clinicians should strongly consider AFM in patients with acute flaccid limb weakness, especially after respiratory illness or fever, and especially between the months of August and November                                
  • CONSIDER POLIO: Clinicians should consider polio in patients with sudden onset of limb weakness, especially in persons who are not vaccinated or under-vaccinated for polio and have traveled to areas with higher risk of polio
  • HOSPITALIZE IMMEDIATELY: Patients with AFM can progress rapidly to respiratory failure. Clinicians should monitor respiratory status of patients and order MRI of the spine and brain with the highest Tesla scanner available. The clinical signs and symptoms of AFM overlap with other neurologic conditions. Therefore, it is critical to consult with specialists in neurology and infectious diseases for appropriate diagnosis and management.
  • LABORATORY TESTING: Clinicians should collect specimens from patients with possible AFM or polio as early as possible in the course of illness (preferably on the day of onset of limb weakness). 
    • The following specimens should be collected: CSF; serum; stool; and a nasopharyngeal (NP) or oropharyngeal (OP) swab.
  • Note, it is critical to obtain twostoolsamples collected at least 24 hours apart, both collected as early in illness as possible and ideally within 14 days of illness onset (poliovirus is most likely to be detected in stool)
  • Coordinate with Snohomish Health District and The Washington State Public Health Laboratories to send specimens to CDC for AFM/polio testing. Additional instructions regarding specimen collection and shipping can be found at:

Case Reporting

Clinicians should report possible cases of AFM (acute onset of flaccid limb weakness AND MRI showing a spinal cord lesion in at least some gray matter, exluding persons with gray matter lesions in the spinal cord resulting from physician diagnosed malignancy, vascular disease, or anatomic abnormalities) or polio to Snohomish Health District using the patient summary form ( Copies of the spinal cord and brain MRI reports, images, and the neurology consult note should be provided along with the patient summary form. Patients with gray matter lesions in the spinal cord resulting from physician diagnosed malignancy, vascular disease, or anatomic abnormalities do not need to be reported.

  • Reports from possible cases of AFM will be submitted to CDC as part of surveillance to help track AFM, understand the spectrum of the disease, detect outbreaks, and inform research.
  • Case classification status (i.e., confirmed, probable, suspect, not a case) is for surveillance purposes and based on consistent and specific criteria to ensure cases being tracked are similar.
  • Clinicians should not wait for CDC’s surveillance case classification to diagnose and manage their patient.

For more information: 



Resources and references for polio:

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