What Parents Should Recognize
The scenario worth knowing is specific: a child who had a cold or a fever in the past week or two suddenly cannot lift an arm, or a leg gives out.
Acute flaccid myelitis is a rare neurologic condition that causes sudden weakness in one or more limbs, with damage to the gray matter of the spinal cord. It predominantly affects previously healthy children, and it can progress quickly, in some cases to breathing difficulty requiring intensive care.
The weakness is the signal. It is flaccid, meaning the limb is limp rather than stiff, and it comes on over hours to days rather than gradually. It frequently follows a respiratory illness or fever by a few days to a couple of weeks.
CDC guidance to clinicians has been consistent across surveillance reports: suspect AFM "in any child with acute flaccid limb weakness," particularly after a recent febrile or respiratory illness.
Escalation signs matter more than the initial weakness. Neck weakness or difficulty holding the head up, facial droop, drooping eyelids, difficulty swallowing, slurred speech, or any change in breathing all indicate the problem may be affecting muscles needed to protect the airway. Those warrant emergency care immediately rather than a call to the pediatrician's office.
What the New Surveillance Report Found
The report published this month is reassuring on frequency, which is worth stating clearly before anything else.
Between 2020 and 2025, the CDC recorded between 17 and 48 AFM cases nationally per year. For comparison, the peak years of 2014, 2016 and 2018 produced 120 to 238 cases annually.
The more interesting finding is that cases stayed low even when the virus most associated with AFM did not. Enterovirus D68, or EV-D68, drove those earlier peaks, and the report notes increases in EV-D68-associated respiratory illness in 2022, 2024, and 2025 without a corresponding rise in AFM.
Why that link appears to have weakened is not established. It may reflect changes in circulating viral strains, population immunity, or factors not yet identified. The honest position is that nobody knows, and nobody can currently predict when or whether cases will rise again.
For a parent, the practical meaning is proportion. AFM is genuinely rare, and the overwhelming majority of children who get a summer respiratory virus will not develop it. Nothing in this report suggests families should worry more this year than last.
Why Late Summer Matters
The seasonality is real, and it comes from the virus rather than from anything about the season itself.
In the peak years, AFM cases clustered in late summer and early fall. That timing tracks enterovirus circulation, which rises as children return to school and shed viruses in close quarters. Enteroviruses are a large family, most of which cause nothing worse than a summer cold, hand-foot-and-mouth disease, or a few days of fever.
So the window from roughly August through October is when clinicians historically have been most alert. That is useful context for a parent trying to judge whether a symptom deserves urgency, and it is also a reason not to over-read it, since low case counts have held through recent seasons regardless of month.
Cases have been reported in 49 states and the District of Columbia over the surveillance period, so this is not a regional concern.
There is no vaccine for EV-D68 and no specific antiviral treatment for AFM. Care is supportive, focused on protecting breathing and swallowing and on rehabilitation afterward. Historical data indicate that roughly half of patients required intensive care and a smaller share required mechanical ventilation.
The Polio Question in the Report
The finding likely to matter most to public health is one a parent might otherwise skip, and it has a simple household action attached.
AFM is, in the report's words, clinically and radiologically indistinguishable from the paralysis caused by poliovirus. A doctor looking at a child with sudden limb weakness and an MRI showing spinal cord lesions cannot tell from those alone which one they are dealing with.
That makes laboratory testing the only way to distinguish them, and the report found a gap. Approximately half of AFM patients had stool specimens tested for poliovirus. The recommendation is that stool specimens should be collected and tested from all patients suspected of having AFM.
The reason this is not theoretical: one polio case was identified in New York in 2022.
The report also found that between 75 and 100 percent of AFM patients had received three or more polio vaccine doses, and its stated implication is that "remaining current with polio vaccinations can reduce the risk for poliovirus infection." For families, that is the concrete takeaway. The routine childhood polio series is protection against the one preventable cause of sudden paralysis.
When to Go to the Emergency Department
The decision rule here is simpler than most, because the threshold for acting is low.
Go to an emergency department, or call 911, for sudden weakness in an arm or leg in a child, particularly following a recent illness. Do not wait for a next-day appointment, and do not wait to see whether it improves. Rapid evaluation matters because the condition can progress and because supportive care is most effective when started early.
Call 911 rather than driving for any difficulty breathing, difficulty swallowing or managing saliva, slurred speech, or a child who cannot hold up their head.
At the hospital, it is reasonable to ask whether AFM is being considered, whether an MRI of the spine is planned, and whether stool and respiratory specimens are being collected. Those questions are appropriate rather than pushy, and given the testing gap the report identified, the stool specimen question is fair.
Confirm your child's polio vaccinations are current at the next well visit. Complaining of tired legs after a long day is not this. Waking up unable to lift an arm is.
The confirmed findings are 17 to 48 annual AFM cases since 2020, well below the peak years, with no rise despite increased EV-D68 activity. Those most affected are previously healthy children, historically in late summer and early fall. Reasonable actions include emergency evaluation for sudden limb weakness and keeping polio vaccination current. The central uncertainty is why the link to EV-D68 weakened and whether cases will peak again. The next expected development is CDC's next annual surveillance update.
Frequently Asked Questions
What is acute flaccid myelitis? A rare neurologic condition causing sudden limp weakness in one or more limbs, with spinal cord damage. It mainly affects previously healthy children.
How common is it? Rare. CDC recorded 17 to 48 cases per year nationally from 2020 through 2025, compared with 120 to 238 in the peak years of 2014, 2016, and 2018.
Is it rising this year? No. The report found cases stayed low even as EV-D68 respiratory illness increased in 2022, 2024 and 2025. Why that link weakened is unknown.
What symptoms mean go to the emergency room? Sudden weakness in an arm or leg, especially after a recent illness. Call 911 for breathing or swallowing difficulty, slurred speech or neck weakness.
Is there a treatment? No specific antiviral exists. Care is supportive, focused on breathing and swallowing, followed by rehabilitation.
What does polio vaccination have to do with it? AFM is indistinguishable from polio paralysis without lab testing. Staying current on polio vaccination protects against the one preventable cause.
Will my child get this from a summer cold? Almost certainly not. Enteroviruses are extremely common and AFM is very rare. The point is recognition, not expectation.
