In the fall of 2014, Kevin Messacar was working at Children's Hospital Colorado when he and his colleagues noticed a string of unusual polio-like cases in youngsters.
Messacar didn’t know it at the time, but they were dealing with the nation’s first outbreak of acute flaccid myelitis or AFM—a virus-fueled neurological condition that affects the spinal cord’s gray matter and can cause paralysis.
There was another spike in 2016, and now a new outbreak is under way. The Centers for Disease Control reported Tuesday that it had confirmed 62 patients with AFM out of 127 suspected cases in 22 states since August.
The average patient age is 4 years old and the symptoms are alarming: facial drooping, sudden weakness in the limbs, a sudden inability to speak.
The current uptick in cases has turned AFM into the scary disease of the month, its “polio-like” ability to attack the nervous system of children leaving parents in fear.
But Messacar, an infectious disease pediatrician and researcher at the University of Colorado, said the public should not panic. While AFM is a serious disease, the panic is "not accurately capturing the picture,” with the chance of getting AFM around one in a million.
The newfound focus on AFM, he said, is being fueled in part being driven by the activism of patient and family groups advocating for their children, often on social media, to help rehabilitate their children.
Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases, agreed.
“As a parent myself, I understand what it is like to be scared for your child,” she said. “Parents need to know that AFM is very rare, even with the increase in cases that we are seeing now.”
Messacar, who has published a series of papers on AFM, said that the most likely culprit is a pair of viruses, enterovirus D68 and A71, which are in the same family as polio but slightly different in structure.
Health officials think that AFM is triggered when D68, A71, or other related viruses (West Nile and Japanese encephalitis have also been linked to it at lower rates) attack a child’s nervous system, allowing AFM to take hold.
Kids who have received the polio vaccine aren’t protected from AFM, and the best prevention advice public health officials can offer is to wash hands and to cough or sneeze into the crook of your elbow.
The pace of this year’s outbreaks is in step with the cycle of enteroviruses.
“Enterovirus D68 has been popping up every two years in the U.S. since 2014,” Messacar said. “The pattern of every two years or so in circulation is a well-described pattern for this family of viruses. For example, enterovirus A71 has been causing widespread epidemics of hand, foot, and mouth disease and neurologic disease in South Asia for the past decade or so with recurring patterns like this.”
The cadence of AFM outbreaks means environmental toxins or a genetic condition are likely not the cause, Messacar said. “Viruses are more likely culprits to what we’ve been seeing cyclically,” he said.
The CDC suggested this week that rhinovirus—closely related to enteroviruses and related to the common cold—could be another culprit.
Messacar said that’s not a bad hypothesis. “If you swabbed the noses of random people on the streets, 40 percent of those with rhinovirus would have no symptoms,” he said. “It’s a common cold [virus] that we’re constantly exposed to. There’s a lot more epidemiological evidence and scientific support for enterovirus D68 an A71 in these cases, even though rhinovirus has been detected in several children.”
Enteroviruses D68 and A71 didn’t just suddenly appear in 2014; scientists have known of their existence since the 1960s, but the virus didn’t appear in these two-year clusters until 2014.
“We didn’t know if this virus would come and go away, or if it would come back and repeat in patterns,” he said. But now that AFM is making a third comeback in a clear biennial pattern, Messacar said that surveillance needs to improve. “We don’t know what’s going to happen in 2020 but seeing the pattern every other year for the past four years means we need to prepare.”
Although rare, the disease is “potentially devastating,” Messacar said. “We haven’t seen cases of permanent paralysis like this since the era of the polio virus. Even though these cases are uncommon, they’re potentially life-changing and can lead to lifelong illness. It should be taken seriously.”