Top 5 Takeaways

1. Biennial Peaks: Acute flaccid myelitis (AFM) cases peaked biennially in 2014, 2016, and 2018, but not in 2020.
2. Case Characteristics: AFM cases in 2019-2020 involved older children and showed more lower limb involvement and less upper limb involvement, prodromal illness, and cerebrospinal fluid pleocytosis compared to 2018.
3. Enterovirus D68 Detection: Enterovirus D68 (EV-D68) was detected in 37 cases in 2018, but only one case in 2019 and none in 2020.
4. Hospitalization Trends: A higher proportion of AFM patients were hospitalized within one day of symptom onset in 2020 compared to 2018.
5. Public Health Vigilance: Clinicians should remain vigilant for AFM in children with acute flaccid limb weakness, especially following febrile or respiratory illness.

Original Article Author and Citation

Corresponding Author

Sarah Kidd, skidd@cdc.gov

Suggested Citation

Kidd S, Yee E, English R, et al. National Surveillance for Acute Flaccid Myelitis — United States, 2018–2020. MMWR Morb Mortal Wkly Rep 2021;70:1534–1538. DOI: http://dx.doi.org/10.15585/mmwr.mm7044a2

Summary

This article reviews the epidemiology of acute flaccid myelitis (AFM) cases in the United States from 2018 to 2020. AFM, a serious neurologic condition affecting children, showed biennial peaks in previous years but did not increase in 2020. The study found that AFM cases in 2019 and 2020 involved older children with more lower limb involvement and fewer prodromal illnesses compared to 2018. Enterovirus D68 was rarely detected in 2019 and 2020, suggesting different etiologies for AFM in these years.

Methods

National AFM surveillance data from 2018 to 2020 were analyzed. Health departments reported cases meeting the clinical criterion for AFM to the CDC, including demographic, clinical, and laboratory information. Data were abstracted from medical records and analyzed to describe trends and case characteristics. Laboratory testing for enterovirus/rhinovirus was conducted on available specimens.

Discussion

The absence of an AFM peak in 2020 deviates from the biennial pattern observed in previous years. The differences in case characteristics and lower detection of EV-D68 in 2019-2020 suggest varied etiologies for AFM. The rapid progression of AFM necessitates immediate hospitalization and respiratory monitoring. Increased public and clinician awareness since 2018 may have contributed to earlier recognition and hospitalization of AFM cases.

Conclusion

AFM cases in 2019-2020 differed significantly from those in 2018, with older children and different clinical presentations. The lack of a 2020 peak may be due to reduced transmission of enteroviruses during the COVID-19 pandemic. Clinicians should continue to suspect AFM in children with acute flaccid limb weakness, especially after febrile or respiratory illness, and report cases to public health departments.

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