Non-polio enteroviruses have been suspected as the primary culprits causing acute flaccid myelitis (AFM).

However, it is clear now that other viruses can cause the illness, noted Emily Erbelding, MD, MPH, director of the Division of Microbiology and Infectious Diseases at the National Institutes of Health (NIH) during a July 21 CDC-sponsored presentation on AFM.1

Erbelding noted there is evidence to suggest many, if not most, cases of AFM detected over the past few years were caused by enterovirus D68 (EV-D68).

“We don’t understand whether the virus damages motor neurons directly or whether the host immune response causes this damage,” she said. “We also don’t understand why some children are uniquely vulnerable to this condition if they become infected with EV-D68 and whether there is some genetic susceptibility.”

These are some of the key questions investigators are seeking to answer in AFM-focused research studies. One notable example is an NIH-funded AFM natural history study coordinated by the University of Alabama Birmingham.2

“The study will allow a large number of sites to collect the standard set of specimens and clinical data according to a common protocol,” Erbelding explained. “It will also support specimen collection in household contacts. This will allow for researchers to define why some children are vulnerable to AFM when their siblings who might also be infected with the same virus do not suffer the same consequences.”

NIH researchers anticipate approximately 40 sites in four different countries will be participating in the study. About half these sites have been activated already, according to Erbelding.

“The sites are diverse in geographic location, and that will allow for a collection of specimens over time so that research can describe the evolution of the virus and also any genetic mutation that might evolve,” she observed. The NIH also is in the early stages of developing a vaccine for EV-D68, according to Erbelding. She noted the agency has been actively collaborating with organizations like the CDC as well as academic investigators and members of affected families to strengthen AFM research efforts.

“There is much more to do in this area,” she said. “We have ongoing efforts to develop and improve animal models for AFM, to improve our diagnostic tests, to develop possible therapeutics such as monoclonal antibodies, and to continue with EV-D68 vaccine development.”


  1. Centers for Disease Control and Prevention. Public health grand rounds. Acute flaccid myelitis: Answering questions through national collaboration. July 21, 2020.
  2. National Institutes of Health. NIH awards contract for acute flaccid myelitis natural history study. July 23, 2019.