Rare Polio-like Illness on the Rise—Again

Rare Polio-like Illness on the Rise—Again

Health officials are bracing for an anticipated seasonal spike in cases of acute flaccid myelitis (AFM). There are still many unknowns about this mysterious illness.

Health officials are ramping up efforts to understand why there are increasing reports of children across the United States with a rare polio-like condition, called acute flaccid myelitis (AFM), which causes weakness and paralysis in the arms or legs.

AFM tends to peak in late summer and early fall but as of July 2019, there were already 11 confirmed cases in eight states—California, Maryland, Nebraska, North Carolina, Pennsylvania, Texas, Utah and West Virginia, according to the Centers for Disease Control and Prevention (CDC).

A total of 233 people in 41 states were diagnosed with AFM in 2018—the highest number of confirmed cases since the CDC began tracking the condition in 2014. While additional suspected cases reported in 2018 remain under investigation, the CDC is anticipating another seasonal spike. On July 10, 2019, health officials reminded doctors to be vigilant and promptly report all suspected AFM cases to their local health department.

“I urge physicians to look for symptoms and report suspected cases so that we can accelerate efforts to address this serious illness,” said CDC Director, Robert Redfield, MD.

Searching for clues
Most of the people diagnosed with AFM are children. In fact, more than 90 percent of those diagnosed with AFM in 2018 were kids with a median age of about 5-years old. More than 90 percent of these patients also had a mild respiratory illness or fever, suggesting they had a viral infection before they developed AFM, the CDC reports.

This recent spike in AFM is part of a rising trend. The CDC began monitoring the condition back in 2014 after noticing an unusual spike in an illness that caused sudden weakness in the arms and legs. Since then, there have been 570 confirmed cases, or between 22 and 233 diagnoses every year. The severity of the 2018 outbreak caused the rare condition to receive even more attention.

The seemingly mysterious polio-like illness captured headlines, fueled concerns among parents and prompted federal health officials to issue warnings about the condition. But what exactly is AFM and how worried should you be?

What is it?
Acute flaccid myelitis is a serious condition that affects the nervous system. People with AFM develop lesions in the gray matter inside their spinal cord. This causes their muscles and reflexes to weaken.

Symptoms of AFM include:

  • Loss of strength or muscle tone in the arms or legs
  • Droopy face or eyelids
  • Trouble moving the eyes
  • Difficulty swallowing
  • Slurred speech
  • Trouble breathing

In extreme cases, AFM may cause paralysis.

Searching for clues
For some people, AFM may be particularly concerning because there are still more questions than answers. It’s unclear why AFM appears to be on the rise, what causes it and how it can be most effectively treated.

Back in 2014, there was an outbreak of respiratory illness among kids, many of whom had asthma and other lung disease, caused by an enterovirus, known as EV-D68, which was linked with AFM, explains Christopher Ohl, MD, an infectious disease specialist at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina. As a result, the CDC began monitoring the condition and testing samples of patients’ spinal fluid and blood for evidence of what might be causing the polio-like illness. This ongoing investigation could help explain the increasing prevalence of AFM.

“There is a high level of scrutiny and if you’re looking for something, you’re going to find more,” Dr. Ohl says.

Several possible causes
The fact that AFM tends to spike in the late summer and early fall, suggests the condition has a seasonal pattern, Ohl adds. The annual resurgence of the condition was also less notable in 2015 and 2017 than it was in 2014 and 2016. Then, cases hit a new high in 2018—in line with this seasonal pattern.

Scientists investigating AFM have identified several possible causes, including toxins in the environment and other viral infections, such as enterovirus and the mosquito-borne illness, West Nile virus. This year, enterovirus EV-D68 (a type of virus that causes an illness similar to a very bad cold), enterovirus A71 (one of many non-polio enteroviruses) and coxsackievirus A16 (hand, foot, and mouth disease) have been pinpointed as possible triggers in some patients, but there is not one clear common link among all AFM cases that fully explains the increasing incidence of the condition.

This likely means that there is more than one cause, Ohl says.

How AFM is diagnosed and treated
The warning signs of AFM may be confused with other neurological disorders, such as Guillain-Barre syndrome (GBS)—a condition that causes the immune system to attack part of the nervous system.

A neurological exam and an MRI are needed to confirm an AFM diagnosis. Some patients may also undergo a spinal tap, which is a procedure that involves checking the cerebrospinal fluid for potential pathogens.

The large variety of treatments that have been used to manage AFM—including antiviral and anti-inflammatory drugs as well as drugs to suppress patients’ immune system response—have not been effective. Unlike other parts of the body, which may heal more readily, damaged nerve tissues take much longer to recover, Ohl explains.

While there is not one specific treatment or cure for AFM, doctors may recommend certain therapies for individual patients, including physical or occupational therapy to help them regain mobility or strengthen their arms or legs.

Some AFM patients may face lingering effects for months or even years, but a full or nearly full recovery over time is possible, he says. Scientists are still trying to figure out why some people recover more fully and quickly than others. Some patients may be genetically more susceptible to the condition, Ohl points out.

Should you be worried?
It’s important to remember that AFM is still very uncommon.

“It’s really, really rare,” Ohl says. “It’s sort of like winning the lottery—not very likely.”

In the U.S., it’s estimated that less than one in a million people will develop the illness each year. By way of comparison, Ohl points out that there will be far more deaths, hospitalizations and long-term effects from the flu this year than from AFM.

What can you do to prevent AFM?
AFM is still under investigation but there are some things you can do to help protect against the viral infections that have been linked to the condition. The CDC recommends taking the following precautions:

  • Make sure you and your children are up to date on your vaccines.
  • Practice good hand hygiene, washing often with soap and water for at least 20 seconds.
  • Take steps to prevent mosquito bites, such as wearing insect repellent.
  • If you notice anyone, particularly a child, experiencing sudden weakness or other symptoms of AFM, you should seek medical attention right away.

The U.S. Centers for Disease Control and Prevention provides more information on its ongoing AFM investigation.

This article was medically reviewed and updated in July 2019.

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