The CDC expects to see clusters of a rare polio-like illness among children this fall

• Acute flaccid myelitis is a rare but serious neurologic syndrome that can cause paralysis in children.
• Reported cases of AFM peak every other year, and an outbreak may be coming in 2020.
• The CDC warns doctors and parents to look out for sudden limb weakness in children.

Doctors and parents should look out for limb weakness in children this fall, the Centers for Disease Control and Prevention said on Tuesday.

It may be a symptom of acute flaccid myelitis, a neurologic syndrome that bears similarities to polio. Cases of AFM tend to spike every other year, with the last surge occurring in 2018.

The syndrome affects mostly children and can cause permanent paralysis and respiratory failure if left untreated. During the 2018 outbreak, 98 percent of AFM patients with the syndrome were hospitalized, a study by the CDC found. The patients had an average age of 5 years old.

The CDC expects 2020 to be another peak year for AFM and released a report to warn health care providers of the possible outbreak.

This year's outbreak coincides with the coronavirus pandemic, which could cause potentially life-threatening delays in AFM diagnosis and treatment.

How AFM differs from polio

Although AFM symptoms resemble those of polio, specimen testing has confirmed that the syndrome is not caused by poliovirus. It is likely a different kind of enterovirus, specifically enterovirus-D68, that causes biennial outbreaks of AFM, according to the CDC.

Enteroviruses are common in the United States in the late summer and fall. They typically cause mild, cold-like symptoms or no symptoms at all, but in rare cases can lead to AFM or other severe illnesses.

AFM shares symptoms with COVID-19

That AFM shares symptoms with COVID-19 could pose a problem for diagnosing and treating the rare syndrome.

Along with sudden limb weakness, early symptoms of AFM include difficulty walking, neck or back pain, fever, and limb pain.

Most patients experience respiratory illness or fever about a week before the onset of muscle weakness.

"We are concerned that, in the midst of a Covid pandemic, that cases might not be recognized as AFM, or we are concerned that parents might be worried about taking their child to the doctor if they develop something as serious as limb weakness," Dr. Thomas Clark, deputy director of CDC's Division of Viral Diseases, told reporters in a telebriefing.

The CDC is preempting delays in medical care due to the pandemic

But as AFM can progress in a matter of hours, it is important that doctors are primed to recognize the syndrome and parents seek immediate medical care if their kids begin showing symptoms.

"Recognition and early diagnosis are critical," CDC Director Robert Redfield, MD, said in a press release.

Read more:

A 7-year-old Texas boy spent 12 days on a ventilator in the fight for his life. His mom says schools should stay closed.

Inside a mobile clinic delivering vaccines to children at home to prevent an uptick in measles during the pandemic

5 signs that a child may be lacking the proper nutrition