This polio-like illness is rare, but can cause lifelong paralysis, so it should be taken seriously. We talked to an expert to find out what parents need to know about AFM.

child in hopsital bed holding parents hand
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Acute flaccid myelitis (AFM), a seemingly random and very scary virus, has been baffling parents and doctors alike for years. The patients, who are mostly children under five years old, complain of upper respiratory symptoms and fever, which rapidly progress into muscle weakness and potential paralysis.

The Centers for Disease Control and Prevention (CDC) reported 633 cases of AFM since August 2014—and in 2018, there were 238 confirmed cases in 42 states. Now the CDC warns that 2020 might be another peak year for AFM, which has experienced an outbreak every two years since 2014.

Before you panic, it's important to note that AFM is a rare condition that affects one in a million people, according to the CDC. Still, parents around the country should familiarize themselves with this terrifying virus. Here's everything you need to know about acute flaccid myelitis.

What Is Acute Flaccid Myelitis?

AFM is an illness similar to polio that affects the spinal cord. Doctors aren't entirely sure about the causes and risks factors, but they have noticed some trends. "All patients have the same story," says Dr. Amy Moore, M.D., a plastic and reconstructive surgeon at the Washington University School of Medicine in St. Louis, who has operated on 12 children with AFM.

Most patients first experience fever, malaise, and irritability—which are also symptoms of common respiratory illnesses. Within a couple of days, the child suddenly becomes unable to move their arm or leg. This rapid limb weakness prompts a visit to the hospital. "Most of the children get sent home with a diagnosis of an infection, then come back two days later paralyzed," says Dr. Moore. In severe cases, the paralysis can affect the muscles surrounding the lungs and impair breathing.

Sarah Hopkins, M.D., MSPH, a pediatric neurologist and Section Head for Multiple Sclerosis and Neuroinflammatory Disorders at Children's Hospital of Philadelphia, adds that muscles closest to the body are generally most affected by AFM. For example, the weakness is worse in the shoulder than the hand. "Once the kid gets weak, there is a period where the weakness gets worse for about five days," says Dr. Hopkins. "Then things stop getting worse, and we'll see some improvements a few days or weeks later."

Who Gets Acute Flaccid Myelitis?

About 90 percent of AFM patients are younger than 18; most of them are under five years old. Nobody knows why younger children are affected most by the disease. Research is currently being conducted to determine the causes and risk factors.

AFM has been linked to two strains of enterovirus: EV-D68 and EV-A71. According to Dr. Hopkins, many sick children tested positive for one of these enteroviruses—but the strains weren't present in every patient, which makes matters even more confounding. Other possible causes of AFM include environmental toxins, genetic disorders, poliovirus, West Nile Virus, and adenoviruses. AFM is likely "a very uncommon complication of a more common virus," explains Dr. Hopkins.

Dr. Moore adds that, in many cases, an entire family comes down with a respiratory illness, but only one child ends up with AFM. She's also never seen two members of the same family with AFM. Because of this, doctors believe that acute flaccid myelitis is not contagious.

Symptoms of Acute Flaccid Myelitis

Symptoms come on very suddenly, so it's important that parents don't panic. A child with AFM may experience:

  • Very sudden loss of the use of an arm or leg
  • Loss of reflexes
  • Facial drooping
  • Slurred speech and difficulty swallowing

In extreme cases, the CDC says AFM may lead to respiratory failure, since it causes the muscles involved in breathing to become weak.

Dr. Moore stresses that AFM affects each child differently, since "where the virus attacks along the spinal cord is variable." Even so, it's important to stay calm, and remember that the disease is rare. "We don't want people being beside themselves every time their child has a cold," says Dr. Hopkins. "The vast majority of children will have a cold and be 100 percent fine. But parents should take their kid to the hospital if there's any sign of muscle weakness"—just to be safe.

In a Vital Signs report released in August 2020, the CDC says that "prompt recognition" and "immediate action" by health care providers is key to achieving the best outcomes. The report claims that 35 percent of patients weren't hospitalized for two or more days after first experiencing weak limbs—and since the disease can progress quickly, these delays can have serious consequences.

What To Do If You Suspect AFM

"Most viral illnesses are almost always benign," says Danelle Fisher, M.D., chair of pediatrics at Providence Saint John's Health Center in Santa Monica, California, and a mom to a 4-year-old son. "Parents shouldn't be overly concerned, but vigilance is key, especially since viruses tend to run rampant this time of year when kids go back to school and temperatures dip."

If you do recognize any AFM symptoms, you should seek medical attention immediately. More than anything, Dr. Fisher says, "parents should use gut instinct." Most kids are going to get over a virus in a few days. But if your child is acting really sick, or doesn't seem like him or herself, and the illness is interfering with daily activities, or he or she can't sleep, contact your pediatrician.

To make a diagnosis, doctors will examine the muscles and conduct an MRI for a better look at the spinal cord. Dr. Moore says doctors may also do a lumbar puncture to remove cerebrospinal fluid from the spine. Examining the fluid can determine if the child has a strain of enterovirus linked to AFM—but it can't diagnose AFM itself.

Treatment for AFM

"The best acute treatment for AFM is still a matter of discussion," says Dr. Hopkins. "No clinical trials support one treatment over the others." Some doctors may rely on immune globulin intravenous (IVIG), which is human plasma from blood donors that contains antibodies to build immune responses. Patients can also undergo surgery for improved muscle function. Dr. Moore has performed 12 surgeries resulting from cases of AFM in 2016. "I give the kids more function than they have now, in order to use what they have left," she explains.

In the long term, physical therapy can help correct AFM symptoms. "Kids typically get slowly better over time with a lot of therapies. We see improvement with intensive therapy," says Dr. Hopkins, adding that "residual muscle weakness" may never go away. If AFM severely impacts the muscles involved in breathing, the patient may need ventilator support.

How to Protect Against AFM

While doctors don't know how to prevent AFM, parents should focus on ways to keep their family healthy. Encourage hand washing, cover coughs and sneezes, and keep kids home from school if they are sick. Also, avoid being around sick people, as viruses are easily passed via coughs, sneezes, and touching infected surfaces.

Dr. Fisher recommends that parents take note of the prevalence of AFM where they live; we often see scattered reports, but clusters can be concerning. The last cluster doctors noted in 2014 paralyzed 120 kids. The CDC's site is a good resource for information, as is the American Academy of Pediatrics site, and your child's pediatrician.