What CDC is Learning about AFM

CDC has been thoroughly investigating the AFM cases since 2014, when we first noted a large number of cases being reported.

CDC’s Investigation Updates

  • Most of the patients with AFM (more than 90%) had a mild respiratory illness or fever consistent with a viral infection before they developed AFM.
    • Viral infections such as from enteroviruses are common, especially in children, and most people recover. We don’t know why a small number of people develop AFM, while most others recover. We are continuing to investigate this.
  • These AFM cases are not caused by poliovirus; all the stool specimens from AFM patients that we received tested negative for poliovirus.
  • We detected coxsackievirus A16, EV-A71, and EV-D68 in the spinal fluid of four of 596 confirmed cases of AFM since 2014, which points to the cause of those patients’ AFM. For all other patients, no pathogen (germ) has been detected in their spinal fluid to confirm a cause.
  • Most patients had onset of AFM between August and October, with increases in AFM cases every two years since 2014. At this same time of year, many viruses commonly circulate, including enteroviruses, and will be temporally associated with AFM.
  • Most AFM cases are children (over 90%) and have occurred in 49 states and DC.
Page last reviewed: December 12, 2019