You’ve probably seen it on the news – a rare, polio-like illness is causing cases of paralysis in children. Here’s the latest info, based on our best current knowledge from the CDC.
Acute flaccid myelitis (AFM) is a sudden illness that causes weakness in one or more extremities – one arm or (less likely) a leg, or any combination of arms and legs. The words in the name express the key features: it’s acute, beginning over hours or sometimes a few days; it’s flaccid, meaning the affected body parts are floppy and weak; and it’s a myelitis, meaning the disease occurs in the spinal cord. The muscles are fine, the brain is fine, but the area of the spinal cord that carries signals to the muscles becomes inflamed and stops working. You can see distinctive changes on an MRI scan of the spine to help confirm the diagnosis.
The first cases of what was later named AFM were reported in California in 2012. The CDC started closely tracking cases of AFM in 2014, when a surge of reports about the illness began to appear in the United States and overseas. Since then, we’ve seen a striking pattern, with most cases occurring in the late summer and early fall, August through October. In the US, we’ve also seen an unexplained pattern where most cases occur in spurts every other year – in 2014, 2016, and now again in 2018. 2015 and 2017 had far fewer cases.
Over 400 cases of AFM have been reported in the US over the last four years, including about 80 in 2018 so far. Most states have reported at least one case, including Georgia. There doesn’t seem to be geographic focus in any area. Overall, the rate is less than one in a million people – AFM is a very rare disease. Almost all cases of AFM have occurred in children, at an average age of 4-6 years.
Several different viral infections have been found in children with AFM, though it’s unclear that these viruses were the cause of the symptoms. The most-commonly associated viruses are from a family called “enteroviruses,” including one that has been implicated in groups of acute severe respiratory disease called enterovirus D68. Other viruses have been investigated including West Nile or Japanese Encephalitis viruses, herpes viruses, and adenoviruses. Most commonly, no specific viral infection is found. The cause of most cases of AFM is unknown.
Still, it seems most likely that a viral infection is the trigger, because of the seasonality of the disease and its propensity to strike children rather than adults. Similar symptoms were once seen with the polio virus, and multiple tests for polio have been performed in children reported with AFM. But it’s never been found — polio itself is not the cause AFM in the United States or abroad. The CDC is continuing to investigate the possibility of one or more viral triggers, an inflammatory condition triggered after a viral infection, or a possible environmental trigger as causes of AFM.
Children with AFM typically have a preceding illness with fever, runny nose, cough, vomiting, or diarrhea 1 to 2 weeks prior to the beginning of AFM symptoms. Often these common viral symptoms have resolved by the time AFM begins, with its rapid onset of limb weakness. There may be near-complete paralysis (inability to move the limb), or varying degrees of weakness. Sometimes, symptoms including stuff neck, headache, or pain in the limbs accompanies the weakness. It’s also sometimes possible for AFM to affect the nerves in the upper neck and head, causing a face or eyelid droop, difficulty swallowing or speaking, or a hoarse or weak voice.
Children with AFM need to be hospitalized. Many tests need to be done to narrow down the diagnosis and rule out other causes of weakness (including blood tests, a lumbar puncture, and MRI scans.) Children with AFM can develop weakness of the muscles that help them breathe, and may need to be treated in an ICU. Neurologists, infectious disease specialists, and public health officials will all help guide care.
There isn’t solid evidence that any specific treatment is effective, since good clinical trials of therapy haven’t been performed yet. It’s been difficult to study AFM because it’s so rare, and the disease progresses quickly. In addition to supportive care, many people with AFM have been treated with intravenous immunoglobulin, steroids, and plasmapheresis. Though some children with AFM have recovered quickly, many continue to have lasting paralysis requiring long-term care.
So what should parents do about this? First, there’s no need to panic. The press and Facebook like to stir up trouble with blaring headlines and clickbait titles – but remember that AFM is really rare, with about 100 or so cases a year occurring across the entire country. Polio caused about 15,000 cases of paralysis a year in the 1950s before a vaccine was introduced. We’ve come a long way, and your children are, overall, far safer than children have ever been from infections, environmental illnesses, and trauma.
Some common-sense steps can probably help. Most cases of AFM seem to have a viral trigger, so avoiding infections is a good idea. Teach your children to practice good handwashing, and keep them out of group care when they’re ill. Though we don’t have a vaccine to prevent AFM, vaccines can prevent the neurologic complications of other infections like influenza, measles, and mumps – so be sure to keep your child fully vaccinated. And seek care immediately if your child becomes weak in one or more limbs.
And, please, support your public health community and the scientists who work to keep your children safe. There’s always another new health challenge out there (Ebola, Zika, SARS, and MERS, to name a few.) We need to keep our public health infrastructure strong to help tackle AFM and whatever the next challenge turns out to be. Go science!
Roy Benaroch is a pediatrician who blogs at the Pediatric Insider. He is also the author of A Guide to Getting the Best Health Care for Your Child and the creator of The Great Courses’ Medical School for Everyone: Grand Rounds Cases.
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