What is acute flaccid myelitis? Minnesota cases raise questions

Mystery illness in Minnesota

Health officials are investigating a rash of rare illnesses causing polio-like symptoms in Minnesota. At least six children in the state have been diagnosed and hospitalized with acute flaccid myelitis (or AFM) since September 20. The Minnesota Department of Health sees, on average, about one case per year.

AFM is an illness that 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. 

Its symptoms are likened to those caused by polio, which was eradicated in the U.S. thanks to the polio vaccine.

Health experts say the disease can lead to paralysis and even death.

AFM is not new, but the Centers for Disease Control and Prevention reported seeing an uptick in cases starting in 2014. Still, the condition is extremely rare, with the CDC estimating that less than one in a million people in the United States will get AFM every year.

What causes AFM?

AFM can occur as a result of a variety of germs including polio virus and non-polio enteroviruses, West Nile virus, and adenoviruses.

However, oftentimes, even with extensive lab tests, the cause of a patient's AFM is not identified.

What are the symptoms of AFM?

Sudden onset of arm or leg weakness and loss of muscle tone and reflexes is common for people with AFM. Additional symptoms can include:

  • Facial drooping or weakness
  • Difficulty moving the eyes
  • Dropping eyelids
  • Difficulty swallowing
  • Slurred speech

Numbness or a tingling sensation is rare in people with the condition, though some people experience pain in the arms or legs. Some people may have difficulty passing urine.

In its most severe form, AFM can lead to respiratory failure. This occurs when the muscles involved with breathing become weak and can require urgent ventilator support through the use of a breathing machine.

In very rare cases, AFM can trigger other serious neurologic complications that could lead to death.

How is AFM treated?

There is no specific treatment for AFM. However, doctors who specialize in treating brain and spinal cord illnesses may recommend certain interventions on a case-by-case basis.

For example, a neurologist may recommend physical or occupational therapy to help with arm or leg weakness.

Health officials say they do not yet know the long-term effects of AFM.

How can AFM be prevented?

Since polio can sometimes lead to AFM, you can protect yourself and your children by getting vaccinated. West Nile virus can also lead to the illness so taking steps to protect your family from mosquito bites, including using mosquito repellent, staying indoors at dusk and dawn when bites are more common, and removing standing or stagnant water near your home, can also help.

Finally, although it's unknown whether it's effective in preventing AFM, the CDC notes washing your hands often with soap and water is one of the best ways to avoid getting sick and spreading germs to others.