Acute Flaccid Myelitis (AFM)


What You Need to Know

Acute flaccid Myelitis (AFM) is a rare but serious condition. It affects the nervous system, specifically the area of spinal cord called gray matter, which causes the muscles and reflexes in the body to become weak. This condition is not new, but the increase in cases starting in 2014 is. CDC estimates that less than one in a million people in the United States will get AFM every year. There are a variety of possible causes of AFM, such as viruses, environmental toxins, and genetic disorders. Most of the cases that CDC has learned about have been in children. There have been 725 confirmed cases since CDC began tracking AFM in August of 2014. CDC has been thoroughly investigating cases since that time. We have seen increases in AFM cases, mostly in young children, in 2014, 2016 and 2018.

As of May 5, 2023, there have been 2 confirmed cases in 2023 out of 15 reports of patients under investigation (PUIs)

Most people will have sudden onset of arm or leg weakness and loss of muscle tone and reflexes. In addition to arm or leg weakness, some will have:

  • Facial droop/weakness,
  • Difficulty moving the eyes,
  • Drooping eyelids, or
  • Difficulty with swallowing or slurred speech
  • Numbness or tingling is rare in people with AFM 
  • Some people have pain in their arms or legs.
  • Some people with AFM may be unable to urinate.

The most severe symptom of AFM is respiratory failure that can happen when the muscles involved with breathing become weak. This can require urgent ventilator support (breathing machine). In very rare cases, it is possible that the process in the body that triggers AFM may also trigger other serious neurological complications that could lead to death.

If you or your child develops any of these symptoms, you should seek medical care right away.  

There is no one test that can diagnose AFM at this time. AFM is diagnosed by an evaluation of several factors: a patient’s signs and symptoms, MRI images and findings, and any laboratory evidence. It is important that the tests are done as soon as possible after the patient develops symptoms.

The disease is not well understood, basic prevention methods are advised:

  • Washing hands with soap and water is one of the best ways to avoid getting sick and spreading illness to others.
  • Stay up to date on all vaccinations.
  • For more information, please visit the CDC AFM website.

AFM in Montana

Figure 1. In 2022, there were no confirmed cases in Montana. 

AFM cases reported in 2022

Figure 2. In 2018, there were 3 confirmed cases in Montana. All were in adults >18 years.

AFM cases reported in 2018