A mysterious syndrome that paralyzed kids seems to have disappeared. But why?

Doctors first identified cases of unexplained muscle weakness and limb paralysis in children, which they called acute flaccid myelitis, or AFM, in 2014 — though in retrospect, sporadic cases showed up as early as 2009, said Kevin Messacar, an infectious disease specialist at Children’s Hospital Colorado [and associate professor of pediatrics at CU School of Medicine]. The hospital was one of the first to raise alarms that something unusual was going on.