The headlines began in 2014: Formerly healthy children contracted what seemed to be a minor upper respiratory infection and were suddenly paralyzed — sometimes one limb, sometimes multiple limbs, sometimes permanently.
Parents and experts wondered if it could be a brand-new virus, West Nile disease, or even a mutated version of polio, which hadn’t been seen in the U.S. since the late 1970s.
They were wrong.
While the 2014 cases included only a handful of children, as of late October there are now 155 patients under investigation — up from 127 a week prior — for what experts have now identified as acute flaccid myelitis (AFM), a condition affecting the nervous system and striking mainly children. The average age of an AFM patient is 4 years old.
Though the condition is still rare, affecting fewer than 1 in a million and occurring mainly in the late summer and fall, scientists still aren’t sure what causes it. There isn’t any significant geographical clustering, and while enterovirus — which typically causes mild coldlike symptoms — has been detected in some cases, experts don’t have enough information to formally single it out as the culprit. Adding to the mystery, the number of cases seems to be cyclical, peaking every other year. Some experts believe this is further evidence of an enterovirus involvement, since one particular strain, D68, is also known to have biannual cycles.
“We have seen an every-other-year pattern in late summer to early fall of a surge in cases in acute flaccid myelitis,” Kevin Messacar, a pediatric infectious disease specialist at Children’s Hospital Colorado in Aurora, told USA Today. “It directly correlates with the time D68 has been circulating at our institution and reported by colleagues in other parts of the country.”
Messacar told USA Today he also believes the number of cases to be much higher than the number reported by the CDC.