Acute Flaccid Myelitis

Acute flaccid myelitis (AFM) is a rare but serious condition that affects the spinal cord, resulting in weakness or paralysis of arms or legs. AFM occurs in all age groups, but has been identified more commonly in children. Possible causes include viruses, toxins and genetic disorders.
The CDC saw an increase in reports of people across the United States with AFM beginning in August 2014. The increase in 2014 occurred mostly in children and seemed to be connected to infection with enterovirus D68. There was another national increase in AFM in 2016, with 144 people in 37 states confirmed to have AFM. National spikes in case counts occurred in the late summer and early fall. After intensive investigation into the situation; the cause is still not yet known. Enterovirus D68 (EV-D68) infection has been found in some cases, but in most cases testing does not yield evidence for EV-D68 or any other infection.

Clusters of cases have been seen in specific communities and states around the country. Clusters identified nationally include:

In August of 2016, the Washington State Department of Health reported a cluster of cases with one fatality. The cases were all children, aged 3-14 years and admitted to Seattle Children’s Hospital with acute neurologic symptoms.
Orange County had 3 confirmed cases of AFM in 2016, all children ages 6, 11 and 13, and all diagnosed in September.


Cases can begin with symptoms of a viral illness, such as fever, cough, or vomiting and diarrhea. Limb pain and weakness then develop several days later. In addition, some patients may experience: 

  • facial droop/weakness
  • difficulty moving eyes
  • drooping eyelids
  • difficulty with swallowing
  • slurred speech
  • numbness or tingling
  • difficulty passing urine
  • respiratory failure, if the muscles involved with breathing become weak
Many cases will have improvement of symptoms over time. But clinical improvement is not universal; it varies from patient to patient and take months to occur. 

Orange County’s Situation

Orange County had 3 children who developed AFM in September, 2016. The children‘s ages ranged from 6-13. These children had symptoms including:
  • 2 of 3 had upper respiratory viral symptoms before developing neurological symptoms
  • All 3 experienced weakness of one or both arms
  • All 3 had abnormalities identified on spinal MRI
  • 2 of 3 were hospitalized
One of 3 was positive for enterovirus (a non-EVD-68 strain) in both throat and stool samples. All testing for a specific infectious etiology was negative for the other two cases.


AFM should be considered when patients present with symptoms of acute flaccid myelitis. Cerebrospinal fluid testing will demonstrate pleocytosis, and MRI findings include a spinal cord lesion restricted to gray matter. CDPH has developed recommendations for providers to test for a specific viral etiology, which include: Providers are recommended to test for a specific infectious etiology by nasopharyngeal and oropharyngeal swabs, wash or aspirates should be collected as early as possible, as well as cerebrospinal fluid, serum and two stool samples. Full CDPH guidance can be found here. Even with aggressive testing, a cause for AFM may not be identified.


Treatment is supportive, no specific treatment for AFM is available.


General disease prevention steps are recommended: Keep up to date on vaccinations to avoid polio- associated AFM. Protect yourself from West Nile virus, which causes AFM and is spread by mosquitoes, by using repellant and removing stagnant water. And always practice consistent hand washing.