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.
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.