Top 5 Takeaways

1. AFM Case Trends Remain Low Post-2018: Confirmed cases of Acute Flaccid Myelitis (AFM) were low from 2019 to 2022, despite an increase in Enterovirus D68 (EV-D68) respiratory diseases observed in 2022.
2. Shift in Clinical and Laboratory Characteristics: Fewer AFM cases during 2019–2021 had upper limb involvement, prodromal respiratory or febrile illness, or cerebrospinal fluid pleocytosis compared to the peak year 2018, indicating a shift in clinical presentations.
3. EV-D68 Detection Declined Among AFM Cases: While EV-D68 was commonly detected in AFM patients in 2018, there was a significant decrease in its detection from 2019 to 2022, with no cases detected in the last three years.
4. Persistent Hospitalization and ICU Admissions: Nearly all confirmed AFM cases resulted in hospitalization, with a significant portion requiring ICU admission and respiratory support, highlighting the severity of AFM cases.
5. Uncertainty in Future AFM Case Increases: Despite the biannual peak pattern observed in previous years, the absence of an increase in AFM cases in 2022 amidst heightened EV-D68 circulation suggests unpredictability in future AFM case trends.

Original Article Author and Citation

Corresponding Author

Sarah Kidd, skidd@cdc.gov

Suggested Citation

Whitehouse ER, Lopez A, English R, et al. Surveillance for Acute Flaccid Myelitis ― United States, 2018–2022. MMWR Morb Mortal Wkly Rep 2024;73:70–76. DOI

Summary

This MMWR report provides an update on the surveillance for Acute Flaccid Myelitis (AFM) in the United States from 2018 to 2022. AFM is a serious neurologic condition that affects the nervous system, primarily in children, leading to acute and often severe paralysis. Historically, biannual peaks of AFM cases were observed, strongly associated with outbreaks of Enterovirus D68 (EV-D68). However, this pattern did not continue post-2018, with a significant reduction in confirmed cases despite continued surveillance and testing.

Methods

The Centers for Disease Control and Prevention (CDC) collected data on confirmed AFM cases reported by U.S. health departments, including demographic, clinical information, and laboratory test results. Confirmed AFM was defined as acute flaccid limb weakness with spinal cord gray matter lesions visible on MRI.

Discussion

The decrease in AFM cases post-2018, even with increased circulation of EV-D68 in 2022, suggests changes in the epidemiological patterns of AFM and possibly the virus itself. The reasons behind the lack of expected increase in AFM cases despite high levels of EV-D68 circulation are not fully understood, with ongoing research needed to uncover potential factors.

Conclusion

The inconsistency in AFM case increases, despite previous patterns linked to EV-D68 circulation, underscores the complexity of predicting AFM outbreaks. Health professionals are encouraged to remain vigilant for signs of AFM, report suspected cases promptly, and ensure timely collection of specimens for laboratory analysis to improve understanding and response to this serious condition.