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Polio-like syndrome caused by several viruses, CDC says

NBC News logo NBC News 11/13/2018 Maggie Fox

a woman lying on a bed: Flaccid myelitis, the frightening polio-like disease leaving some children partially paralyzed. © NBC News Flaccid myelitis, the frightening polio-like disease leaving some children partially paralyzed. A polio-like condition called acute flaccid myelitis is likely caused by viruses, and probably not just a single virus, the Centers for Disease Control and Prevention said Tuesday.

Patients with the condition almost all have shown symptoms of a viral infection before they developed the muscle weakness or paralysis that marks the condition, CDC researchers said in a new report.

The viruses include the main suspect, EV-D68, but also a related virus called EV-A71 and a few others, a CDC research team said.

"Almost all patients with AFM have reported signs and symptoms consistent with viral illness in the weeks preceding limb weakness," the CDC team, led by Susannah McKay of the CDC's viral disease division, wrote in their report.

So far this year, the CDC has confirmed 80 cases of acute flaccid myelitis or AFM. Another 20 suspected cases are not AFM, the CDC said.

It's the third year that has seen an increase in the number of cases. There were also cases in 2014 and 2016. That every-other-year pattern fits a viral disease, doctors say.

The CDC has struggled to identify the cause of AFM or to say why it seems to have increased in recent years. It's still extremely rare, having affected just 400 people since 2014.

Parents and doctors who treat AFM have become increasingly impatient with the CDC. But the agency says the tests that have been done on patients don't always tell a complete story.

AFM is not caused by vaccines, the CDC said, and the agency has stopped saying it suspect some sort of toxin might be involved.

"I'm glad to see they now recognize that AFM is likely viral," Dr. Ken Tyler, a neurologist at the University of Colorado School of Medicine, told NBC News. "I'm also glad they stopped mentioning 'toxins' and other totally unsubstantiated etiologies (causes). Basically they are slowly coming around," he added.

Viruses can cause a range of nervous system side-effects, including AFM but also: Guillain-Barre syndrome; a similar condition called transverse myelitis; as well as meningitis and encephalitis.

Polio is the best-known cause of paralysis and muscle weakness but none of the patients with AFM has tested positive for polio, the CDC says. Polio has been eradicated in the U.S., although it still circulates in Afghanistan and Pakistan.

"Parents and caregivers are urged to seek immediate medical care for a child who develops sudden weakness of the arms or legs," the CDC advises.

Doctors should ask about respiratory symptoms in any child with sudden onset of muscle weakness, and should take respiratory, stool and spinal fluid samples as soon as possible.

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