The Main Suspect Behind an Ominous Spike in a Polio-like Illness
A common virus seems to be behind a puzzling condition thats paralyzing children, but uncertainties remain.
AFM is a new term, but not a new syndrome. Its package of symptoms can be caused by a wide range of factors, including, as the Centers for Disease Control and Prevention notes, poliovirus, West Nile virus, environmental toxins, and genetic disorders. The question isnt what causes AFM per se, but what is specifically behind the biennial spikes that have appeared since 2014. (There was a small peak in 2012, too, before the condition came to national attention.)
That has proven to be a tough problem to crack. In this era, it seems that scientists could easily grab tissue samples, sequence the genes of everything in them, and pinpoint some consistent microbial culprit. But that hasnt happenedso far, no single germ has shown up in every case. Despite all the tools of modern science, new diseases, especially rare ones, can be very hard to understand.
Afm is uncommon enough that a hospital might get just a handful of cases in a given year, if any. Many centers must join forces to pull off a rigorous studyand thats logistically complicated. The condition is also geographically unpredictable. Some places had cases in 2014 but none this year, and vice versa.
More importantly, its too risky to take biopsies of the actual affected tissuesthe nerves of the brain and spine. Instead, doctors have mostly drawn and analyzed samples of spinal fluid, and theres no guarantee that whatever causes AFM is actually there.
So far, most of the signs point toward a virus as the cause, and specifically some kind of enterovirus. Unlike influenza, which circulates in the winter, enteroviruses are infections of the autumn, which is when AFM cases peak. They mostly infect young children, and the average AFM patient is 4 years old. Enteroviruses need a large enough population of susceptible hosts in which to circulate, so many lie low after waves of infection and crop up in cycles of two or three yearsjust as AFM does. And although many enteroviruses circulate widely but have little effect, they have a track record of occasionally infecting the spinal cord and causing paralytic illnesses.