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Acute Flaccid Myelitis Surveillance - United States, January 2020-December 2025

Adriana S Lopez1, Randall English1, Shannon L Rogers1

  • 1National Center for Immunization and Respiratory Diseases, CDC.

MMWR. Morbidity and Mortality Weekly Report
|July 9, 2026
PubMed

Insights

Nationwide surveillance from 2020-2025 shows low acute flaccid myelitis (AFM) cases, despite enterovirus circulation. Polio vaccination did not prevent most AFM cases, highlighting the need for continued vigilance and reporting.

Area of Science:

  • Neurology
  • Infectious Diseases
  • Public Health Surveillance

Background:

  • Acute flaccid myelitis (AFM) is a serious neurologic condition causing paralysis, particularly in children.
  • AFM is clinically and radiologically indistinguishable from poliovirus-induced acute flaccid paralysis.
  • Nationwide AFM surveillance in the U.S. began in 2014 due to a recognized increase in cases.

Purpose of the Study:

  • To provide an update on nationwide surveillance of confirmed AFM cases from January 2020 to December 2025.
  • To assess the association between enterovirus circulation, particularly EV-D68, and AFM case trends.
  • To evaluate the polio vaccination status of AFM patients and the role of surveillance in detecting other vaccine-preventable diseases.

Main Methods:

  • Analysis of nationwide surveillance data for confirmed AFM cases reported to the CDC.
  • Monitoring of enterovirus circulation, including EV-D68, through sentinel surveillance sites.
  • Review of clinical and laboratory data, including stool specimen testing and polio vaccination status.

Main Results:

  • Confirmed AFM cases remained low (17-48 annually) from 2020-2025, significantly lower than peaks in 2014, 2016, and 2018.
  • Despite seasonal enterovirus circulation and increased EV-D68 respiratory illnesses in 2022, 2024, and 2025, no concurrent increase in AFM cases was observed.
  • EV-D68 was detected in only one AFM patient specimen during the surveillance period; most AFM cases occurred in vaccinated individuals.
  • A polio case in an unvaccinated person was identified through AFM surveillance in 2022.

Conclusions:

  • Current nationwide surveillance indicates a low incidence of AFM despite ongoing enterovirus activity.
  • The majority of AFM cases occurred in individuals up-to-date with polio vaccination, suggesting other factors may be involved.
  • AFM surveillance remains crucial for detecting other serious conditions, including polio, emphasizing the importance of clinical reporting and sample collection.

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