Late last year, six children in Minnesota were diagnosed with a rare, potentially paralyzing and deadly nervous system condition called acute flaccid myelitis or AFM. It starts with just a droopy eye and a slightly slumped face. Within just a few days, reflexes begin to lose their sharpness, while the arms and legs become weaker. If left without therapy, the nervous system continues to become damaged, the ability to breath becomes strained, and paralysis can take hold. Per the Centers for Disease Control and Prevention, the most severe symptom of AFM is respiratory failure caused by weakening of the diaphragm muscles. If this begins to occur, the patient requires urgent medical intervention so they can be placed on a ventilator. In a small number of cases, the processes driving AFM have triggered other serious neurologic complications, leading to death.
"What we're looking at is a disease indistinguishable in most respects from traditional polio, in terms of its symptoms," says Dr. Keith Van Haren, a pediatric neurologist at Stanford University School of Medicine. "Until now it was a really rare bird. Before 2012, we saw maybe one case every five years that wasn't attributable to West Nile. Since 2012, we've seen many more cases."
More and more children are falling sick with this polio-like illness. However, there are currently a few solid ideas about how it develops, how it can be treated, or even what it is exactly. Due to the similarity of the symptoms, the condition was long believed to be caused by the poliovirus. However, the world is fast approaching an eradication of polio, yet the rates of AFM are continuing to rise. A boom of AFM cases was documented in 2014 across the US, the UK, and continental Europe. From August 2014 to January 2019, there were 551 confirmed cases of AFM, with 2018 seeing one of the biggest seasonal waves of the recent epidemic. The CDC notes it's still extremely rare, affecting less than one to two in a million children in the US in a given year.
A new study claims an evidential link between AFM and the enteroviruses-a group of viruses that cause a number of infectious illnesses which are usually mild-is "circumstantial but strong". "As it unfolds, the AFM story seems to be getting more complicated," the study authors write. "Could we be entering some kind of new epidemic era, in which fundamental but unappreciated determinants of enterovirus evolution and spread are changing?"
The trajectory of AFM over the past 5 years suggests that the problem is getting worse, and so it is critical that we fuel our efforts to learn more about, and respond adequately to, this ubiquitous, often crippling, continually reemerging group of viruses.
