CDC AFM surveillance update: confirmed cases stayed low (2020–2025), but test for polio
CDC updated national surveillance reporting for acute flaccid myelitis (AFM) in a July 9, 2026 MMWR report. The new update finds that confirmed AFM cases stayed relatively low from January 2020 through December 2025—but it reiterates a critical diagnostic step for clinicians and public health: when AFM is suspected, doctors and health departments should still collect and test stool specimens for poliovirus.
That testing emphasis matters because AFM can be clinically and radiographically indistinguishable from paralytic poliomyelitis. “Lower AFM incidence” does not mean polio can be ignored during AFM-like evaluations.
What CDC found in its AFM surveillance update
CDC reports 172 confirmed AFM cases across the surveillance period, including:
- 2020: 34
- 2021: 29
- 2022: 48
- 2023: 19
- 2024: 25
- 2025: 17
CDC also contrasts this with earlier U.S. peaks—linked to enterovirus circulation in 2014, 2016, and 2018—when AFM counts were higher at 120–238 cases per year. In plain terms: the 2020–2025 period was “lower” than those peak years.
Why “low AFM” still requires polio testing
AFM is part of a broader clinical syndrome called acute flaccid paralysis. In CDC’s report, the key public-health point is straightforward: if symptoms and imaging suggest AFM, the workup still has to rule out paralytic polio.
In the 2020–2025 period, CDC reports that:
- Approximately one half of AFM patients had stool specimens tested for poliovirus.
- 75%–100% of AFM patients had received at least 3 polio vaccine doses.
- In 2022, one poliomyelitis case in New York was identified through poliovirus testing of stool specimens collected during AFM surveillance.
CDC’s takeaway for clinicians and health departments is that AFM-like cases should trigger stool collection and poliovirus testing to avoid diagnostic misses.
What clinicians and public health agencies should do
CDC emphasizes a practical workflow:
- Ensure stool samples are collected from people with an acute onset of flaccid weakness or paralysis when AFM is suspected.
- Report cases to local health departments so AFM and polio surveillance can be completed.
In CDC’s surveillance framework, if a stool specimen tested for poliovirus is positive, that patient would be classified as a confirmed paralytic poliomyelitis case rather than AFM—underscoring why the testing step is essential.
What families should take away
If someone—especially a child—develops sudden weakness or flaccid paralysis, the message is not to wait. Seek urgent medical evaluation, because part of the medical evaluation for AFM-like presentations may include stool testing to rule out serious causes such as poliovirus.
CDC also notes that staying up to date with polio vaccination remains important for long-term protection against paralytic polio.
What to watch next
CDC will continue AFM surveillance updates. For clinicians and families, the steady “watch next” takeaway is the same: if AFM-like symptoms appear, health systems should not skip stool collection and poliovirus testing just because confirmed AFM counts were lower in 2020–2025.
Sources
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