The last large outbreak of AFM was in 2018—and the CDC says the US is due for another one.

By Amanda MacMillan
Updated August 06, 2020
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The US Centers for Disease Control and Prevention is warning parents of a possible outbreak of a rare, potentially deadly disease in children in the coming months—but it won't be the first time the disease has impacted the younger population.

The illness—known as acute flaccid myelitis, or AFM—is an uncommon but life-threatening neurological condition that mainly affects children, according to the CDC, and the organization has been tracking the disease since 2014. Since then, larger outbreaks of cases have occurred every other year. The last large outbreak occurred in 2018, with 238 total confirmed cases in 42 states, per the CDC database—that's compared to 2019, during which the US reported just 46 cases in 18 states.

As of July 31, the CDC has confirmed 16 cases of AFM—but because it's still extremely early in the season (AFM peaks between August and November), and because the US is due for a larger outbreak like the one that occurred in 2018, experts are urging parents to take the illness seriously. "[AFM] is a medical emergency that requires immediate recognition and care," CDC director Robert Redfield, MD, said on a media conference call Tuesday, per ABC News. Here's what everyone, especially parents, need to know about AFM—and why early detection is key for this potentially deadly illness.

What is acute flaccid myelitis, exactly?

So, AFM is a serious, sometimes fatal condition that affects the nervous system—specifically the area of the spinal cord called "gray matter," which accounts for how the brain sends messages to the body, and vice-versa. In affecting this portion of the spinal cord, AFM causes the muscles and reflexes in the body to weaken.

Since the CDC began tracking AFM in 2014, most cases—about 90%—have been in children, with an average age of 5 years old. However, AFM can also rarely occur in adults. Unfortunately, though, not much is known about AFM—in fact, information is so scarce that in 2018, the CDC established an AFM Task Force to help find answers for what causes the illness, and how to improve treatment methods.

What are the symptoms of acute flaccid myelitis?

The most common sign of AFM is the sudden onset of arm or leg weakness, or a loss of muscle tone or reflexes, per the CDC. Past that, some less-common symptoms include:

  • Drooping eyelids
  • Difficulty moving the eyes
  • Facial drooping or weakness
  • Difficulty swallowing
  • Slurred speech
  • Leg or arm pain
  • Neck or back pain
  • Numbness or tingling
  • Inability to pass urine

AFM can also have quite severe symptoms, like respiratory failure, when the muscles used in breathing become too weak to work. It can also lead to changes in body temperature or blood pressure, which can be life threatening. In some cases, AFM can cause permanent paralysis.

According to the newest Vital Signs report from the CDC, 2 in 3 patients sought care at the emergency department for AFM, and 98% of all patients were hospitalized—over half of which were admitted to the ICU, while 1 out of every 4 hospitalized patients needed help with breathing through a ventilator.

What worries doctors most about a possible uptick in AFM cases, is the possibility of delaying treatment. The CDC notes that a third of patients who experienced limb weakness were hospitalized two or more days after the onset of their symptoms—and because AFM can progress quickly, doctors urge for faster recognition and care for the best outcome.

What causes acute flaccid myelitis?

That's the thing: Doctors don't entirely know what leads to an AFM diagnosis. Most patients, however, had respiratory symptoms or a fever possibly linked to a viral infection less than a week before the onset of their symptoms, per the CDC.

Non-polio enteroviruses—which can cause mild to sever respiratory symptoms like a runny nose, sneeze, and a cough—are thought to play a large role in the development of AFM. Enterovirus D68 (EV-D68) in particular, typically resulted in severe illness, leading to hospitalization or even ventilation.

It should also be noted that AFM was previously thought to be caused by polio or poliomyelitis, an infectious disease that also attacks the spinal cord and can cause permanent paralysis. But, fortunately, in all the research done since 2014, none of the stool samples taken from any AFM patient tested positive for poliovirus, signaling that polio is not linked to AFM.

COVID-19, too, may impact the possible upcoming AFM peak, according to Robert Glatter, MD, an Emergency Physician at Lenox Hill in New York City, per ABC News. "We expect that AFM will likely have another peak in 2020," he said. "That said, it's still unclear if or how COVID-19's recommended social distancing measures and attention to mask wearing and hand hygiene will impact how much enterovirus we end up seeing, along with cases of AFM." He added that some symptoms of AFM may overlap with COVID-19, as can some of the same hygiene precautions used to protect against both viruses.

How is acute flaccid myelitis treated—and is there any long-term damage?

Unfortunately, AFM can be difficult to diagnose, since it's so similar to other neurological diseases like transverse myelitis (inflammation of the spinal cord) and Guillain-Barre syndrome (a disorder in which a person's immune system damages their nerves). Different tests and exams—like MRIs, nerve conduction tests, and lab tests can help doctors come to the most accurate diagnosis.

The CDC also says that there's currently no specific treatment for AFM—which is why early diagnosis is crucial for the best possible outcome. That said, doctors may prescribe immunosuppressant drugs, steroids, and blood-replacement procedures. They may also recommend physical or occupational therapy to help patients get their strength and mobility back after experiencing muscle weakness or paralysis.

AFM, however, is best avoided through proper hygiene practices, like handwashing, and social distancing, since it's mainly caused by viruses.

Though doctors continue to stress that even though AFM is incredibly rare—even during a larger outbreak of cases—the best thing for parents and doctors is to simply be aware of the possibility of AFM and to seek medical care as soon as possible for children with the specific symptoms.

For now, the CDC will also continue to work on finding proper treatment for AFM, as well as continuing to search for specific causes of the illness. "We've learned a lot, but we have a lot to learn about AFM," Dr. Redfield said during the media conference. "We are working at CDC and collaborating with the NIH on a couple of prospective large studies, which will help us better understand risk factors for AFM."

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