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Red Book Online Outbreaks: Acute Flaccid Myelitis

July 11, 2024


As of July 1, 2024, there has been 10 confirmed cases out of 19 reports of patients under investigation (PUIs) in 2024 and 18 confirmed cases out of 40 reports of PUIs in 2023. See map AFM Cases and Outbreaks | CDC. There have been 755 confirmed cases since CDC began tracking AFM in August of 2014. CDC has been thoroughly investigating cases since that time. We have seen increases in AFM cases, mostly in young children, in 2014 (120 cases), 2016 (153 cases) and 2018 (238 cases). CDC recently announced that in August 2022 there was an increase of enterovirus (and specifically of EVD68) detected in children reported in some regions in the U.S. (Health Alert Network No. 474). Pediatricians were encouraged to be alert for cases of Acute Flaccid Myelitis, however despite the respiratory outbreak of EV-D68 in 2022, no significant increase in AFM cases was observed. 

Acute flaccid myelitis (AFM) is a rare, polio-like illness. It primarily affects young children, but there have been cases among adolescents and adults. AFM cases in the U.S. have peaked between August and October, with increases in cases seen biennially in 2014–2018. Early detection and medical support are critical to improve long-term health outcomes of children with AFM. Delays in recognition can put children at risk. Pediatricians and pediatric health care providers who can identify AFM and promptly hospitalize patients are well positioned to provide optimal medical care.

Clinical Guidance

  • Presentation: The most common symptoms of AFM are sudden onset of arm or leg weakness, loss of muscle tone, and loss of reflexes. Suspect AFM in any child presenting with acute onset weakness, particularly when following a febrile illness in the summer-fall. Detect AFM through a detailed neurologic exam for hypotonic, hyporeflexic limb weakness.
  • Diagnosis: Diagnose AFM by obtaining MRI of the brain and spinal cord, and lumbar puncture. Collect respiratory swabs, stool, CSF, and blood as early as possible to look for a cause.
  • Complications: AFM can lead to long term complications, including paralysis, and in rare cases, death.
  • Precautions: Contact precautions are indicated for infants and young children for the duration of enterovirus illness. Droplet precautions also are indicated for EV-D68 respiratory infections.
  • Risk mitigation: Prevent infection by promoting vaccination (ie Inactivacted poliovirus vaccine) and infection control practices (eg hand hygiene, especially after diaper changes, and disinfecting surfaces).
  • Management: Manage AFM by hospitalizing any suspected cases in the acute phase and providing respiratory support when needed. Get help from AFM experts by consulting a pediatric neurologist, infectious disease specialist or through the AFM physician support portal.
  • Treatment: There is no specific treatment for AFM, recommendations for interventions are made on a case-by-case basis related to the needs of the child and consultation with specialists. For more information see CDC clinical guidance.
  • Reporting and assistance: Report any suspected cases of AFM to your state health department and provide requested biological specimens and data.


Pediatric Practice Tools and Information

Recognize AFM: AFM Clinical Presentation for Clinicians ׀ CDC

Initial Evaluation for AFM ׀ CDC

AFM Clinical Guidance | CDC


Public Health Resources

Report cases: AFM Case Definitions | CDC

Collect data: Data Collection for AFM | CDC

State and Local AFM Contacts for Clinicians | CDC


Information for Patients and Caregivers

AAP AFM: What We Know About This Paralyzing Illness
In Spanish: Mielitis flácida aguda (MFA): qué sabemos sobre esta enfermedad paralizante

CDC information: For Parents of Children who have AFM | CDC


Infection Prevention and Control Resources

Project Firstline (

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