What CDC Is Learning about AFM

CDC has been tracking and investigating AFM since 2014, when the United States recorded a large increase in AFM cases.

Who, When, Where, and What puzzle pieces.

Since 2014, we have learned that

  • Most AFM cases have been in children (over 90%).
  • AFM has occurred in children and adults in 49 states and DC.
  • Increases in AFM cases have occurred in 2014, 2016, and 2018.
  • Non-polio enteroviruses, particularly EV-D68, are likely responsible for the increases in AFM cases in those years.
  • Stool specimens that we receive from AFM patients are tested for poliovirus. If poliovirus is detected, it is considered a case of polio, not a case of AFM.

Evidence that points to enteroviruses

  • Most patients with AFM had mild respiratory symptoms or fever before they developed AFM, which is consistent with a viral infection.
  • The increases in AFM cases occurred at about the same time of year when enterovirus circulation is most common in the United States.
  • We have detected coxsackievirus A16, EV-A71, and EV-D68 in the spinal fluid of a small number of patients with AFM, which points to the cause of their AFM. For all other patients, no pathogen (germ) has been detected in spinal fluid to confirm a cause.
  • Patients with AFM had antibodies against enteroviruses in their spinal fluid more often than those without AFM. Having antibodies against a virus means that a person was previously infected with the virus.