AFM (Acute Flaccid Myelitis) is a paralyzing syndrome caused by lesions to the spinal cord, mostly in the areas that control muscles.

AFM patients are primarily children, although there have also been reported cases in adults. Symptoms typically include a preceding febrile respiratory illness followed by sudden onset of limb weakness and loss of muscle tone and reflexes. In addition to limb weakness, some patients have cranial nerve involvement and present with facial droop/weakness, difficulty moving the eyes, drooping eyelids, or difficulty with swallowing or slurred speech. This can include muscles that control the arms, legs, torso, face, as well as talking, swallowing, and breathing. Paralysis is flaccid (floppy and weak), rather than spastic (stiff and weak).

Although a definitive cause for AFM has not yet been established, many experts think it is due to infection with a non-polio enterovirus, such as EV-D68. At this time, however, a definitive cause has not yet been determined.

Clinicians should report all patients they suspect have AFM to their health departments as soon as possible.
— Centers for Disease Control and Prevention