Scientists now believe they may have identified the cause of acute flaccid myelitis, abbreviated AFM. This polio-like illness has affected around 600 children since it was first detected almost a decade ago. The disease starts with flu-like symptoms but rapidly turns into muscle paralysis. After the respiratory symptoms subside, some kids are left with long-term nerve damage that makes it hard to move arms or legs. In the worst cases, breathing is also affected.
That progression of symptoms was also true of polio, though a strong vaccination campaign has essentially eliminated polio in the U.S. A large number of AFM cases appeared in 2014, 2016 and 2018. As soon as these cases began appearing, scientists tried to figure out the cause.
What Is the Cause of AFM?
The researchers were able to rule out polio virus very quickly. At least three years ago, they were focusing on an enterovirus as a possible cause. Investigators have now confirmed that enteroviruses are probably responsible (Nature Medicine, Oct.21, 2019).
Usually these common viruses cause mild illness with cold-like symptoms. Once the infection has passed, the viruses aren’t easily identified. Consequently, the researchers used a tool called VirScan to identify antibodies. According to the article, this tool identifies “481,966 overlapping peptides derived from all known vertebrate and arboviruses (VirScan).”
Enteroviruses in Nervous System Fluid:
Around 70 percent of the AFM patients have antibodies to enteroviruses in their cerebrospinal fluid, compared to just 7 percent of kids with other neurological diseases. At this point, the most likely culprit is EV-D68. Besides the antibodies, epidemiology supports closer examination of this non-polio enterovirus. It caused many more infections than usual in 2014, 2016 and 2018, corresponding to the appearance of multiple cases of AFM.
Scientists will need to do more research to determine how this virus causes such harm in a small proportion of children. Ideally, they will come to understand how best to help them. Hopefully, a vaccine will be developed against the enterovirus in the near future to prevent this devastating condition.