Acute Flaccid Myelitis Surveillance — United States, January 2020–December 2025

Acute flaccid myelitis (AFM) is a rare but serious neurologic condition that causes paralysis and primarily affects children. Clinically and radiologically, AFM is indistinguishable from the acute flaccid paralysis of poliomyelitis caused by poliovirus. Nationwide surveillance for AFM has been conducted in the United States since 2014, when an increase in AFM was first recognized. Laboratory testing and epidemiologic and clinical data collected through surveillance suggest that enteroviruses, particularly enterovirus D68 (EV-D68), are a common cause of AFM. EV-D68 circulation was associated with biennial peaks in AFM cases in the United States in 2014, 2016, and 2018. This report provides an update to nationwide surveillance of confirmed AFM cases during January 2020-December 2025. During this period, the number of confirmed AFM cases reported to CDC remained low (17-48 cases per year) compared with 2014, 2016, and 2018 (120-238 cases per year). Despite ongoing seasonal enterovirus circulation, including increases in EV-D68-associated respiratory illnesses identified from sentinel surveillance sites in 2022, 2024, and 2025, concurrent increases in AFM cases in nationwide surveillance data were not observed; EV-D68 was detected in one AFM patient specimen received by CDC during this period. A majority (approximately 75%) of confirmed cases of AFM occurred in persons who were reported to be up to date with polio vaccination; approximately one half had stool specimens collected and tested. In 2022, a polio case in an unvaccinated person was identified by testing stool specimens collected through AFM surveillance. Clinicians should ensure that stool samples are collected from patients with acute onset of flaccid weakness or paralysis and report all cases to their local health department.