Mysterious Polio-Like Illness AFM May Be Linked to Common Virus

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Researchers are learning more about a mysterious condition called actue flaccid myelitis that can lead to paralysis. Getty Images
  • Researchers think they’ve figured out why some children develop a serious condition called acute flaccid myelitis (AFM).
  • AFM can cause lesions on the spinal cord that can result in paralysis. Often it’s temporary, but some children have had symptoms for months.
  • Scientists think a type of virus called an enterovirus may be the answer behind the rising cases of AFM.

Since 2014, researchers have been stumped by the rise of a rare but potentially devastating disease that acts similarly to polio and mainly affects children.

Acute flaccid myelitis, or AFM, is an illness that can result in paralysis and even require people to be put on ventilators.

While researchers believed it was connected to a viral illness, they’ve been baffled by its cause and how to prevent it.

Now, in a new study published in the journal, Pediatrics, researchers have come closer to understanding the cause of AFM by examining cases between 2015 and 2017.

The scientists discovered that although AFM is most likely triggered by a viral infection — especially a common type of virus called enterovirus — no single strain of virus was identified as a definitive cause.

AFM is an illness that affects the nervous system, particularly the spinal cord, causing the body to weaken. It usually manifests after an infection.

The term acute flaccid myelitis was only coined in 2014 when there was an outbreak of 120 cases. But the illness had symptoms similar to the polio virus, a development that’s been especially worrying for health officials and parents.

While polio has been eradicated from the United States thanks to the polio vaccine, this new disease has no vaccine.

There are a range of symptoms including difficulty lifting an arm or leg, to having severe difficulty with the muscles that help with breathing.

The majority of cases of people who had AFM reported fever, cough, runny nose, vomiting, and diarrhea — many of the symptoms of the common cold.

Although many of these symptoms may go away, limb weakness is an early sign the nervous system is being affected.

In the most severe forms of this illness, AFM can lead to respiratory failure necessitating ventilator support because the muscles have become so weak they cannot allow spontaneous breaths.

Each year there has been a growing number of AFM cases in the United States.

In 2014 there were 120, in 2016 there were 153 confirmed cases, and in 2018 there were 236. The largest incidence of cases occurred during the late summer to early fall months.

The disease was first spotted when an initial outbreak took place in late summer 2014 where 120 cases of AFP were diagnosed. Several of these cases were among children in Colorado. All cases were between August and December with a peak in the late summer and early fall.

One lead in the search for the cause of AFM is the enterovirus. There are many strains of the common enteroviruses and they usually result in mild symptoms like cough, cold, and runny nose.

The enterovirus D-68 is the only known pathogen that had a correlation with the AFM outbreaks in 2014. But scientists acknowledge that there isn’t enough evidence linking one virus as the single cause of AFM.

“This is interesting as it resembles more of the polio virus because it does live in the intestinal tract, hence the name enterovirus,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center in Tennessee.

“However, this is an enterovirus that is transmitted very readily by the respiratory route,” he added.

In 2018, another strain, the enterovirus A-71, was also associated with many AFM cases.

Both A-71 and D-68 are part of the enterovirus family — the class responsible for other viruses including the polio and coxsackie viruses.

“Enterovirus D-68 appears to play a role, but it does not account for all cases” said Dr. Michael Grosso, chief medical officer and chair of pediatrics at Northwell Health’s Huntington Hospital in New York.

Researchers studied 193 confirmed cases and 25 probable cases in children from 43 states between 2015 and 2017 with most cases occurring in 2016.

With the first outbreak being in 2014, the initial hopes were that this was a one-time occurrence. However, additional cases occurred in 2016 and then in 2018.

With this biennial pattern, experts are concerned that there could be another outbreak in 2020.

According to the CDC, most people will experience sudden onset of arm or leg weakness and loss of muscle tone and reflexes.

Although less common, some people also experienced facial drooping or weakness, difficulty moving their eyes, eyelid drooping, difficulty swallowing, slurred speech, and even pain in the arms and legs.

“Certainly, the onset of otherwise unexplained limb weakness should prompt evaluation by a physician,” said Grosso.

Although there are less common symptoms associated with the condition, Grosso agreed that “these problems may have causes other than AFM, but they may still represent other important neurological conditions.”

The National Institutes of Health has partnered with the University of Alabama at Birmingham to further study this illness by granting $10 million over 5 years.

The CDC also established an AFM Task Force in 2018 comprised of scientists, physicians, and public health officials from many institutions to assist in the ongoing investigations surrounding these cases.

“The emphasis on good hygiene and trying to avoid people who have respiratory infections or who are otherwise ill is currently the best preventive admonition” added Schaffner.

Currently there are no specific treatments for AFM except for supportive therapy or treatments.

Grosso’s advice to parents is: “For the moment, since there is already so much to worry about when rearing healthy children, don’t devote too much [energy] to thinking about this rare condition that you are very unlikely [to] ever encounter.”

Rajiv Bahl, MD, MBA, MS, is an emergency medicine physician and health writer. You can find him at RajivBahlMD.



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