Causes & Prevention of AFM

  • We think viruses, including enteroviruses, likely play a role in AFM. We don’t know why a small number of people develop AFM, while most others recover.
  • All the stool specimens from AFM patients that we received tested negative for poliovirus.
  • There is no specific action to take to prevent AFM.

Possible Causes of AFM

Our five years of surveillance data have contributed important evidence to support the role of viruses, including enteroviruses, in AFM.

Most patients had respiratory illness or fever

  • Since 2014, more than 90% of patients with AFM had a mild respiratory illness or fever consistent with a viral infection before they developed AFM.
  • Respiratory illnesses and fever from viral infections such as from enteroviruses are common, especially in children, and most people recover. Enteroviruses can also cause neurologic illness, such as meningitis, encephalitis, and acute flaccid limb weakness, but these are rare. We don’t know why a small number of people develop AFM, while most others recover. We are continuing to investigate possible causes for this including:
    • Direct infection of a virus on the motor neurons (nerves that make the muscles move)
    • Indirect infection where a virus may lead to an inflammatory or immune response directed toward motor neurons
    • Host genetic factors in which certain children may be more susceptible than others

Increase in cases between August and October

  • Most patients had onset of AFM between August and October, with increases in AFM cases every two years since 2014.
  • Many viruses commonly circulate between August and October, including enteroviruses, and will be temporally associated with AFM. CDC is working with national partners to understand the annual circulation of enteroviruses, including EV-D68, and what association it may have with AFM.
  • The large number of AFM cases identified in 2014 coincided with a national outbreak of severe respiratory illness caused by EV-D68.

Detecting the causes of AFM

CDC has tested many different specimens from AFM patients for a wide range of pathogens that can cause AFM.

  • We detected coxsackievirus A16, EV-A71, and EV-D68 in the spinal fluid of 4 out of 551 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.
  • All the stool specimens from AFM patients that we received tested negative for poliovirus

Often times, despite extensive testing of AFM patients, no pathogens are found in the spinal fluid. This may be because the pathogen has been cleared by the body or it is hiding in tissues that make it difficult to detect. Another possibility is that the pathogen triggers an immune response in the body that causes damage to the spinal cord. We are searching for what triggers AFM in some children who have had a fever and/or respiratory illness compared to most children who don’t get AFM.

Prevention

There is no specific action to take to prevent AFM.

Since we don’t know the cause of most of these AFM cases or what triggers this condition, there is no specific action to take to prevent AFM. However, most children had a respiratory illness or fever consistent with a viral infection before they developed AFM.

You can decrease risk of getting viral infections by:

You can decrease the risk of spreading viral infections by:

  • Cleaning and disinfecting frequently touched surfaces, including toys and doorknobs
  • Covering coughs and sneezes with a tissue or upper shirt sleeve, not hands
  • Keeping sick children at home