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

• CDC MMWR (July 9, 2026): Acute Flaccid Myelitis Surveillance — United States, January 2020–December 2025