The Centers for Disease Control and Prevention sent out a message this month asking doctors to look out for cases of acute flaccid myelitis, which causes muscle weakness or paralysis. AFM, as it’s known, has followed a two-year pattern since 2014, with a spike in cases from August to November in even years and relatively few cases in odd years.
Most kids who developed AFM had a common respiratory virus roughly a week earlier, so it’s not clear if precautions meant to prevent the spread of COVID-19 will reduce the number of cases, said Dr. Kevin Messacar, a pediatric infectious disease researcher and physician at Children’s Hospital Colorado and University of Colorado. There’s no sign the virus believed to cause AFM was circulating in Colorado as of the second week of August, he said.
Still, it’s important for parents to be on the lookout for symptoms, because once nerves die, the damage can’t be repaired, Messacar said. About 75% of kids they followed at Children’s Hospital Colorado have some long-term muscle weakness, though physical therapy to strengthen surrounding muscles can help, he said.
Symptoms to watch for include:
- Difficulty walking
- Trouble talking or swallowing
- Facial drooping
- Pain in the neck, back, or limbs
- Not using one or more limbs normally
The disease isn’t fully understood. The CDC believes enterovirus D68 is a major cause, though other common viruses could be behind some cases. Enteroviruses are a family that includes poliovirus, but EV-D68 typically causes cold-like symptoms. EV-D68 was first identified in the 1960s, but didn’t attract much attention until the 2000s, when more kids started showing up with difficulty breathing, and later with muscle weakness, Messacar said. It’s not clear why it started making kids sicker in recent years, he said.
Even in years with more cases than usual, AFM is rare. The CDC recorded 238 cases in 2018, with most in the late summer or fall. About half of patients were admitted to an intensive care unit, and almost a quarter needed a ventilator to breathe. Most were young children, though cases have been reported in teens and adults.
The reason for the two-year pattern isn’t known with certainty, but common respiratory viruses do tend to follow a cycle, dipping after significant numbers of people were infected and coming back later, Messacar said. With EV-D68, it could reflect many children getting infected in school or daycare, so that the virus only gains a foothold again after enough younger, unexposed kids start attending.
“There just needs to be enough susceptible people out there,” he said.
Parents don’t need to be alarmed about common cold symptoms, but they should seek help immediately if a child is struggling to breathe or shows signs of muscle weakness, Messacar said. Weakness, in this sense, doesn’t mean the general wiped-out feeling when you’re sick, but difficulty with basic functions like walking, talking or swallowing, he said.
“This is a child who wakes up and can no longer lift their arm,” he said.
Studies in mice show the virus can attack the spinal cord, but patients also tend to have substantial inflammation from the immune system’s response, Messacar said. Researchers are still studying which is the culprit in paralysis cases, so they know whether it’s better to treat patients with antiviral or anti-inflammatory drugs, he said. Work on a potential vaccine also is ongoing.
Many people get EV-D68, and very few develop AFM. Still, it’s important to study vaccines and treatments, in case it becomes a more common syndrome, Messacar said. That happened with polio, which has existed for thousands of years but only began causing large outbreaks in the 20th century, he said.
“The goal is to study diseases while they’re still uncommon and rare, so if they do become common, you have tools in your toolbox,” he said.
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