AFM - General Information


About Acute Flaccid Myelitis

Acute flaccid myelitis (AFM) is an illness characterized by acute onset of flaccid limb weakness and magnetic resonance imaging (MRI) showing lesions in the gray matter of the spinal cord.

Most AFM cases have arm and/or leg weakness coupled with loss of muscle tone and reflexes. Additionally, some cases have facial/eyelid drooping, difficulty swallowing, slurred speech, difficulty moving their eyes, and/or pain in their arms and legs.

AFM activity peaks in the late summer and early fall and nationwide outbreaks have occurred on a biennial (i.e., every other year) basis since 2014. As of January 3, 2020, there have been 603 confirmed AFM cases reported to the Centers for Disease Control & Prevention (CDC), including 16 cases from Illinois.

While the cause of AFM has not been identified, it is hypothesized that a viral agent (e.g., enterovirus D68) is involved, as almost all (90%) AFM cases had a preceding respiratory illness and/or fever, increased incidence of AFM cases typically coincides with EV-D68 outbreaks, and viral agents (e.g., EV-D68, EV-A71, Coxsackievirus A16) have been detected in the spinal fluid of a small number of AFM cases.

For more information on acute flaccid myelitis, visit the dedicated CDC and IDPH webpages.

AFM - Reporting and Lab

Case Definition, Reporting, and Specimen Collection/Submission Guidelines

Reminder: Clinicians should continue to be vigilant and report all patients under investigation that meet the clinical criteria for acute flaccid myelitis (i.e., sudden onset of flaccid limb weakness) to the Chicago Department of Public Health (CDPH) regardless of any laboratory results or MRI findings.

AFM Case Definition, 2020

In 2020, the CDC updated the AFM case definition, which is used to ensure consistent and accurate case classification for surveillance purposes. All patients under investigation for AFM will receive final classification by a team of expert neurologists.


Clinical Criteria: An illness with onset of acute flaccid weakness of one or more limb

Laboratory Criteria:

  • Confirmatory laboratory/imaging evidence: MRI showing spinal cord lesion with predominant gray matter involvement and spanning one or more vertebral segment (excluding lesions caused by physician diagnosed malignancy, vascular disease, or anatomic abnormalities)
  • Presumptive laboratory/imaging evidence: MRI showing spinal cord lesion where gray matter involvement is present but predominance cannot be determined (excluding lesions caused by physician diagnosed malignancy, vascular disease, or anatomic abnormalities)

Case Classification:

  • Confirmed
    • Clinically compatible case with confirmatory laboratory/imaging evidence, AND
    • Absence of a clear alternative diagnosis attributable to a nationally notifiable condition
  • Probable
    • Clinically compatible case with presumptive laboratory/imaging evidence, AND
    • Absence of a clear alternative diagnosis attributable to a nationally notifiable condition
  • Suspect
    • Clinically compatible case, AND
    • Available information is insufficient to classify case as probable or confirmed

Reporting and Specimen Collection/Submission Guidelines

If you have a patient under investigation (PUI) with acute onset of flaccid weakness in one or more limbs:

  1. Collect specimens as close to the onset of limb weakness as possible and store according to the table below:


  1. Contact the Chicago Department of Public Health (CDPH) via the CDPH Reportable Disease Hotline at 312-743-9000.  A CDPH representative will provide you with an authorization number that you will need for specimen submission to the Illinois Department of Public Health (IDPH).
  2. Complete the CDC Patient Summary Form  (Instructions). Also gather the MRI report and the MRI images. Send a copy of these documents to CDPH. Note that another copy will need to go to IDPH with your specimens for testing.
  3. Complete the IDPH Communicable Diseases Laboratory Test Requisition Form. On the top of the form, write the authorization number that was provided to you by CDPH.
  4. Complete one CDC Specimen Submission Form (also known as the CDC 50.34 Dash Form) per specimen. When completing the form, select "Human" in the "Specimen origin" drop down at hte top left of the form. Select "Enterovirus Detection and Identification" for the "Test order name" field. Enter "CDC-10312" in the "Test order code" field.  Reminder: If you are submitting multiple specimens, you must complete one form per specimen.
  5. Ship specimens, along with the CDC Patient Summary Form, IDPH Communicable Disease Laboratory Test Requisition, and the CDC Specimen Submission Form(s), to:  

       Illinois Department of Public Health Laboratory

Attn: Virology

2121 W. Taylor Street

Chicago, IL 60612


IDPH Lab Contact Phone Number: 312-793-4760


  1. If you are a clinician or infection control practitioner with access to enter reportable diseases into the Illinois National Electronic Disease Surveillance System (I-NEDSS), please enter the case’s information into the system’s AFM module. Note: Clinicians or infection control practitioners interested in becoming I-NEDSS users must first register for an IDPH Web Portal account.

Last updated: January 29, 2020

AFM - Contact Us

For Clinical Questions or to Report Suspect Cases, Contact:

The CDPH Disease Reporting Hotline at



When to Report

Clinicians should continue to be vigilant and send information to Chicago Department of Public Health (CDPH) for all patients under investigation (PUI) with sudden onset of neurologic illness associated with limb weakness that meet the case definition for Acute Flaccid Myelitis. Clinicians should send information for PUIs who meet the case definition regardless of any laboratory results.


Alerts & Communications

AFM SIREN Alert (IDPH, August 2019)

AFM Update (CDC, May 2019)

AFM Letter to Chicago Providers (CDPH, September 2018)


AFM - Symptoms


AFM is characterized by a sudden weakness in one or more limbs, often accompanied by loss of muscle tone and decreased reflexes.  In addition, some patients may have:

  • Facial droop/weakness
  • Difficulty moving the eyes
  • Drooping eyelid(s)
  • Difficulty with swallowing or slurred speech


AFM Symptoms