Acute Flaccid Myelitis (AFM)


Acute flaccid myelitis (AFM) is a disease that affects the nervous system, specifically the spinal cord, characterized by rapid onset of weakness in one or more limbs and distinct abnormalities of spinal cord gray matter on magnetic resonance imaging (MRI), which can result from a variety of causes.

As of January 1st, 2016 acute flaccid myelitis (AFM) was made a temporarily reportable disease.


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

  • facial droop/weakness
  • difficulty moving eyes
  • drooping eyelids
  • difficulty with swallowing or slurred speech
  • numbness or tingling
  • pain in arms or legs
  • difficulty passing urine
  • respiratory failure, if the muscles involved with breathing become weak


Acute flaccid myelitis (AFM) can be caused by a variety of agents, including several viruses such as:

  • enteroviruses (polio and non-polio)
  • West Nile virus (WNV) as well as other arboviruses, specifically Japanese encephalitis virus and Saint Louis encephalitis virus
  • herpesviruses, such as cytomegalovirus and Epstein-Barr virus
  • adenoviruses

Other agents that can cause AFM include:

  • environmental toxins
  • genetic disorders
  • Guillain-Barre syndrome


There is no specific treatment for AFM, but a neurologist may recommend certain interventions on a case-by-case basis.


Prevention of acute flaccid myelitis includes many of the same techniques to prevent infections from many viral infections including:

  • being up to date on all recommended vaccinations, including poliovirus
  • mosquito protection, including repellent and avoidance
  • washing your hands often with soap and water
  • avoiding close contact with ill people
  • cleaning surfaces with disinfectant 

Reporting suspected cases of AFM

As of January 1st, 2016 acute flaccid myelitis (AFM) was made a temporarily reportable disease. 

Report any illness that meets the following criteria:

  • a person with onset of acute limb weakness, AND
  • a magnetic resonance image showing a spinal cord lesion largely restricted to gray matter, and spanning one or more spinal segments, OR
  • cerebrospinal fluid (CSF) with pleocytosis (CSF white blood cell count >5 cells/mm3, may adjust for presence of red blood cells by subtracting 1 white blood cell for every 500  red blood cells present); CSF protein may or may not be elevated

Clinicians should report suspected cases to Rob Ramaekers at (515) 850-8273 or 1-800-362-2736.

Specimen Collection

Clinicians should collect specimens from patients suspected of having AFM as early as possible in the course of illness, preferably on the day of onset of limb weakness, including

  • cerebrospinal fluid (CSF),
  • blood (serum and whole blood),
  • a nasopharyngeal aspirate, nasopharyngeal wash, or nasopharyngeal swab with lower respiratory specimen if indicated, and an oropharyngeal swab, AND
  • stool, preferably two stool specimens collected as soon after onset of limb weakness and separated by 24 hours.

Early specimen collection has the best chance to yield a diagnosis of AFM. Additional instructions regarding specimen collection and shipping can be found at AFM Specimen Collection Instructions.

Call Rob Ramaekers at the Iowa Department of Public Health at (515) 850-8273 or 1-800-362-2736 to arrange specimen shipment to CDC.  


Beginning in August 2014, CDC received an increase in reports of people across the United States with AFM for which no cause could be found. Since then, CDC has been actively investigating this illness. We continue to receive reports of sporadic cases of AFM. From In 2016, a total of 149 people in 39 states across the country were confirmed to have AFM.  No cases of AFM were reported in Iowa in 2017. 

Graph of national trend of acute flaccid myelitis cases

Additional Resources

(515) 242-5935  |  1(800) 362-2736  |  Submit questions online at "Contact Us"