Number of confirmed acute flaccid myelitis (AFM) cases reported to CDC by month of onset

AFM: acute flaccid myelitis; CDC: Centers for Disease Control and Prevention; MRI: magnetic resonance imaging; CSTE: Council of State and Territorial Epidemiologists.
* Confirmed AFM cases that CDC has been made aware of as of November 1, 2019 with onset of the condition through August 31, 2019. The case counts are subject to change.
¶ The data shown from August 2014 to July 2015 are based on the AFM investigation case definition: onset of acute limb weakness on or after August 1, 2014, and a MRI showing a spinal cord lesion largely restricted to gray matter in a patient age ≤21 years.
Δ The data shown from August 2015 to present are based on the AFM case definition adopted by the CSTE: acute onset of focal limb weakness and an MRI showing spinal cord lesion largely restricted to gray matter and spanning one or more spinal segments, regardless of age.