AFM: The scary polio-like illness

By | November 11, 2018

It is a scary illness, not just for parents but for doctors, too: Acute flaccid myelitis (AFM) causes sudden weakness and loss of muscle tone in the arms and legs and can go on to cause even more serious problems.

It’s not just the symptoms that are scary. It’s also scary because we don’t know what causes it. Although the symptoms are similar to polio, patients with AFM have tested negative for polio. At one point it was thought that it was caused by another enterovirus, but that didn’t end up being the explanation. It may be another virus, or it may be some sort of toxin, or something else entirely — or perhaps a combination of factors.

What we do (and don’t) know about AFM

We know that AFM is more common in children, and we know that cases spike in summer and fall. We know that the symptoms are like those caused by viruses such as enterovirus, adenovirus, or West Nile virus, but after that there’s not much we know. Because we have been following this illness only since 2014, we don’t know the long-term effects of it either. Some patients recover quickly and completely, but for others the weakness doesn’t go away.

AFM symptoms

The symptoms of AFM include:

  • weakness in the arms or legs or both
  • loss of muscle tone in the arms or legs or both. This means that not only are the arms or legs weak, they seem looser or floppier than usual.
  • In some cases, symptoms can also include:
    • weakness of the muscles of the face, which may cause the face to droop
    • trouble moving the eyes
    • weakness of the eyelids, so that they droop
    • trouble talking
    • trouble swallowing
    • trouble breathing.
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If your child shows any of these symptoms, call your doctor right away.

Treating AFM

Because we don’t know exactly what is causing AFM, we don’t have a definitive treatment. We support patients when they are sick, giving medicines to help their symptoms, and physical therapy and other such treatments that may help with weakness, but there is no medicine we can give to cure or even treat the illness itself.

AFM and public health

And to make things even scarier, the number of cases is on the rise. So far in 2018, there have been 62 confirmed cases (127 have been reported as possible cases, but 62 have been confirmed). In all of 2017, only 33 cases were confirmed. Since 2014, there have been 368 confirmed cases. Getting exact numbers on this illness is hard, as there is no clear test for it. The Centers for Disease Control and Prevention (CDC) uses clinical symptoms as well as findings on MRI (magnetic resonance imaging) of the brain to decide whether someone has AFM. Because not all patients get MRI testing, and because not all patients get reported to the CDC, it’s likely that the numbers are higher.

What parents need to know

Since we don’t know exactly what causes AFM, it’s hard to tell people how to prevent it. You can prevent polio by being vaccinated, and everyone should be vaccinated. West Nile virus can cause similar symptoms and avoiding mosquito bites is the best way to prevent that. The best advice we can give now to prevent the viruses that might cause AFM is the simplest: wash your hands, well and often.

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Despite all this scary stuff, it’s important to remember that overall this is a rare disease — less than one in a million people get it.

Harvard Health Blog