Acute Flaccid Myelitis (AFM)

What is acute flaccid myelitis?

Acute flaccid myelitis (AFM) is a condition that affects the nervous system, specifically the spinal cord. Most patients have sudden onset of limb (arm and leg) weakness. AFM is thought to be caused by infections with different types of viruses. The infections most commonly mentioned with AFM include polio or West Nile virus and related infections. Most patients with AFM have a respiratory illness or fever before their limbs are affected. Other causes of AFM are still being explored and may include environmental toxins or genetic disorders.

Who gets AFM?

Anyone of any age can get AFM, but it is more commonly reported in children.

How is AFM spread?

AFM is not spread from person to person. The viruses that are believed to cause AFM may be contagious from one person to another or may be spread by a mosquito or other vector depending on which virus causes the AFM.

What are the symptoms of AFM?

Most patients will have sudden onset of limb weakness and loss of muscle tone and reflexes. In addition, some patients will experience:

  • facial droop/weakness,
  • difficulty moving the eyes,
  • drooping eyelids, or
  • difficulty with swallowing or slurred speech.

Numbness or tingling is rare in patients with AFM, though some people have pain in their arms or legs. Some patients with AFM may be unable to urinate. The most severe symptom of AFM is respiratory failure, which happens when the muscles involved with breathing become weak. This can require urgent ventilator (breathing machine) support.

How soon after exposure do symptoms appear?

The incubation period and time until symptom development depend on which virus is causing the illness.

How is AFM diagnosed?

A doctor can tell the difference between AFM and other diseases with a careful examination of the nervous system, looking at the location of the weakness, muscle tone, and reflexes. Magnetic resonance imaging (MRI) can be very helpful in diagnosing cases of AFM. Laboratory tests on biological specimens, including cerebrospinal fluid (CSF), serum, and stool, are needed to confirm the virus responsible for illness.

What is the treatment for AFM?

There is no specific treatment available for AFM other than supportive care to relieve symptoms. More information about treatment can be found at:

How can AFM be prevented?

The diseases that might cause AFM can be prevented in different ways. The best way to prevent polio is through vaccination. Practicing good hygiene can reduce the risk of infection, such as by hand washing, covering noses and mouths when sneezing or coughing, and not sharing cigarettes, straws, cups, glasses, or eating utensils. Cleaning surfaces with a disinfectant is also helpful. For diseases that are spread by mosquitoes, wearing insect repellent and long sleeves and long pants help prevent bites.

How can I get more information about AFM?

October 2018