Acute flaccid myelitis (AFM)

AFM Cases in WA and the U.S.
Reported Since August 2014 and Confirmed by CDC

Last updated November 3, 2019

Year WA U.S.
2014 0 120
2015 0 22
2016 10 153
2017 3 37
2018 11 236
2019 1 22

Q: What is acute flaccid myelitis (AFM)?

A: AFM is a rare condition with sudden weakness of one or more arms or legs. Sometimes there is also muscle weakness in other parts of the body, such as the face or throat. In severe cases, breathing muscles can be impacted. In all cases, there are distinctive lesions in certain areas of the spinal cord seen by magnetic resonance imaging – an MRI.

  • Symptoms of AFM vary in severity and type – from mild weakness of a limb to complete inability to move legs and arms.
  • Medical information from suspected cases are sent to expert neurologists at the CDC who do a case analysis and decide if the person has AFM or not. If not, the suspected case is “ruled out” and not counted as an official case.

Q: How common is AFM?

A: AFM is quite rare. Less than one person in a million will ever develop it.

  • In 2019, to date, there has been one case confirmed by the CDC in WA.
  • In 2018 there were 11 cases of AFM confirmed in WA.
  • AFM cases seem to increase every other year in WA and the US (see chart).

Q. What causes AFM?

A: There is no single known cause of AFM. It has been associated with a variety of germs, such as enteroviruses, which typically cause mild illness such as respiratory infections. Other possible causes may be West Nile virus, autoimmune diseases or environmental toxins. For most reported cases across the US, the cause has not been identified. AFM can also be mistaken for conditions that cause inflammation of the nerves such as transverse myelitis and Guillain-Barré syndrome.

Polio virus can cause AFM, but it was eliminated in the US by routinely vaccinating children to prevent the disease. Nevertheless, testing for polio is sometimes done because in some other parts of the world, outbreaks of polio still happen among unvaccinated people.

Q: Do you know what caused any of WA's cases?

A. At this point we do not know what has caused AFM cases in our state.

  • In the cases where germs have been found, no single type of germ has consistently been detected.
  • Oftentimes, despite extensive laboratory testing, a cause for AFM can't be identified.
  • It's not known why some people develop AFM while others don't.

Q: Is AFM contagious?

A: The cause of most AFM cases is unknown, but many of the common germs that may cause AFM are contagious, for example enteroviruses, which typically cause mild illnesses such as respiratory infections. On rare occasions enteroviruses can get into the central nervous system and cause more serious illnesses like inflammation of the brain.

  • Some of the germs that cause AFM spread between people while others can't. For example, West Nile virus (WNV) only spreads by mosquitos, while common cold germs are spread between people. Most people who get either of these infections do not develop AFM.

Q: How is AFM diagnosed?

A: AFM is difficult to diagnose because the symptoms can look nearly identical to other conditions or syndromes. AFM is diagnosed based on a combination of symptoms, laboratory tests, and an MRI – which shows the spinal cord lesions – a unique feature of AFM, and essential to diagnosing it.

Q: Could AFM cases be something else?

A: Medical tests to find out if there may be other causes for the illnesses are done before the medical records are reviewed by DOH and sent to the CDC neurologists for AFM analysis. And, because the spinal cord of someone who has AFM has very unique lesions shown in their MRIs, AFM diagnosis is thought to be a reliable diagnosis.

Q: Can adults get AFM?

A: Yes, but it seems more likely to affect children, perhaps because they typically haven't built up as much immunity to germs as adults.

Q: Is there a treatment?

A: There is no specific treatment for AFM other than what doctors call ‘supportive care,' which means treating symptoms. However, a doctor who specializes in treating brain and spinal cord illnesses (neurologist) may recommend certain interventions on a case-by-case basis.

Q: Do people who get AFM get their movement back?

A: The long-term effects of AFM are different for each person. Some patients diagnosed with AFM recover quickly and completely, and others can have a range of continued paralysis requiring ongoing care.

  • Local health departments follow up with medical providers 60 days after symptom onset to find out whether there is lasting weakness in limbs or other areas that were affected. This information is sent to CDC for their ongoing research into the illness.

Q: Is there any way to prevent AFM?

A: AFM can be caused by different things. Because doctors know so little about the cause, there are no known specific ways to prevent it. Many people who've had AFM were sick with an illness like a cold – sometimes with fever or other symptoms a week or two before developing arm or leg weakness. Therefore it is thought that at least some cases of AFM may happen after being infected by one of a number of viruses. Simple steps to avoid illnesses such as good hand washing will lower your risk of getting sick.

You can help protect yourself by:

  • Washing your hands often with soap and water,
  • Avoiding close contact with sick people, and
  • Cleaning surfaces with a disinfectant, especially those that a sick person has touched.
  • Staying up to date on your flu shot and other recommended immunizations.