Acute flaccid myelitis has a calendar. Cases cluster in late summer and early fall, which is why the CDC's publication of six years of surveillance data this month lands a few weeks before the window opens rather than during it.
The headline finding is a quiet one. Between January 2020 and December 2025, the United States recorded between 17 and 48 AFM cases annually. That is a fraction of what the country saw during the biennial peaks of 2014, 2016, and 2018, when annual counts ran from 120 to 238.
