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Chase Kulakowski, 3, contracted AFM two years ago. Getty Images

Health officials are alarmed by growing waves of a paralyzing illness in children. So far the disease has only affected a few hundred children in the United States, but the exact cause and best treatment for this disease remain unknown.

Known as acute flaccid myelitis, or AFM, this rare illness can sometimes cause respiratory failure or even death.

There were 228 confirmed cases of AFM in the United States in 2018, with increases every two years since 2014, reports the Centers for Disease Control and Prevention (CDC).

“There has been a rise of cases with each cluster, but whether that means there are more cases or we are getting better at recognizing them is difficult to say,” said Dr. Mark Hicar, an assistant professor of pediatrics and a pediatric infectious disease specialist at the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo.

Several European countries, as well as Canada and Japan, have also reported cases of AFM.

In the United States, 90 percent of cases have been in children.

Dr. Peter Gill, a pediatrician and researcher at the Hospital for Sick Children in Toronto, said on the CMAJ Podcasts last year said the illness typically affects children between 4 and 15 years old.

Most people have symptoms of a viral infection — such as fever or mild upper respiratory illness — before they develop AFM.

This is followed by sudden onset of “flaccid paralysis,” which Hicar said appears as a floppy leg or arm, with little or no muscle tone in the limb.

People may also have other symptoms, such as drooping eyelids or face, slurred speech, or difficulty swallowing.

If the muscles that control breathing are weakened, people can develop respiratory failure. As a result, they may need to be put on a ventilator to help them breathe.

In some cases, AFM can trigger serious neurologic complications that could cause death.

As of today, the CDC is not aware of any deaths related to AFM in 2018 or 2019, but it reports one death in 2017 in a child with AFM.

Scientists suspect that viruses likely play a role in AFM, although more research is needed to confirm this.

“We do not know the cause of AFM in these recent clusters of cases,” said Hicar. “However, certain viruses with similarity to polio are leading candidates.”

One clue is that most people who developed AFM first had symptoms of a viral illness. AFM cases also peak between August and October, the usual season for enteroviruses, a group of viruses that include the poliovirus.

There are also several non-polio enteroviruses that are responsible for millions of illnesses each year. Only a small number of people develop a serious complication from these.

Since 2014, the CDC has detected non-polio enteroviruses in the spinal fluid of four patients with AFM. However, there has been no sign of poliovirus in stool samples from patients with AFM.

Doctors diagnose AFM based on a patient’s symptoms, the presence of a virus in the spinal fluid, on MRI images of the brain and spinal cord, and other tests.

Hicar said “a number of therapies have been done for AFM, mostly targeting the immune system, but none have shown clear efficacy.”

Treatments include steroids, drugs to boost the immune system, and filtering the blood. They are largely used on a case-by-case basis.

Deaths from AFM are uncommon, especially with early treatment. But Gill said “unfortunately most patients do have some form of lasting impairments.”

Questions about the cause of AFM and the best treatment have left many parents of affected children and physicians hoping for more.

In November, the CDC announced an AFM Task Force to bring together experts from several fields to solve this public health problem.

One thing they hope to clear up is whether the number of cases will continue to rise.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, wrote Tuesday in the journal mBio that “the trajectory of AFM over the past five years suggests that the problem is getting worse.”

“Although theoretically possible,” said Hicar, “we have had three peaks of small numbers of cases in the last five years.”

So it’s hard to know. And without a good understanding of the cause of AFM, it’s also unclear how many people who are infected with an enterovirus develop AFM.

Although AFM is a serious condition, Hicar cautioned people keep it in perspective.

Since 2014, a few hundred children have developed AFM, it is much less common than other causes of injuries in children, such as automobile accidents.

“The potential for lifelong paralysis of a limb is scary, however we need to remember that these are rare events,” said Hicar.