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acute flaccid myelitis

In 2012, CDPH began receiving reports of patients with an unusual condition called acute flaccid myelitis (AFM). Since then, there have been statewide and nationwide spikes in AFM cases noted in the summer and fall months of 2014, 2016 and 2018. 

AFM patients are primarily children, although cases have also been reported in adults. Symptoms typically include a preceding febrile respiratory illness followed by sudden onset of limb weakness and loss of muscle tone and reflexes. In addition to limb weakness, some patients have cranial nerve involvement and present with facial droop/weakness, difficulty moving the eyes, drooping eyelids, or difficulty with swallowing or slurred speech.

Although a definitive cause for AFM has not yet been established, experts think many cases are due to viral causes, which include non-polio enteroviruses (EV-D68, EV-A71), flaviviruses (West Nile virus, Japanese encephalitis virus), herpesviruses, and adenoviruses. To better understand the potential causes, optimal treatment, and outcomes of AFM, CDPH is conducting enhanced surveillance for AFM cases. Enhanced surveillance includes viral testing at CDPH Viral and Rickettsial Diseases Laboratory (VRDL) to identify causes of AFM. 


Most patients with AFM will have sudden onset of limb weakness and loss of muscle tone and reflexes. Some patients may also experience:

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

If you or your child develops any of these symptoms (PDF), you should seek medical care right away.   


Although a viral cause is suspected, it is still unknown why some people develop AFM. There is no specific action to take to prevent AFM. However, it is always important to practice disease prevention steps, such as washing hands frequently, avoiding close contact with people who are sick, covering coughs and sneezes, and cleaning frequently touched surfaces. To learn more about AFM, visit the CDC Acute Flaccid Myelitis website.

Reporting AFM Cases 

  1. Clinicians should report any person with onset of acute flaccid* limb weakness to patient's local health department (LHD)(PDF) regardless of laboratory testing or MRI results.
  2. Clinicians should collect specimens for potential public health testing and order a spinal MRI as soon as possible. Collect serum, CSF, nasopharyngeal swab, oropharyngeal swab and two stool specimens (collected 24 hours apart). Pathogen-specific testing should also continue at hospital laboratories as determined by the patient's clinical picture.
  3. Work with the LHD to:
    • complete the AFM Patient Case Summary Form (PDF);
    • send MRI reports and images;
    • send neurology consult notes; and
    • send specimens to the CDPH VRDL to hold while the LHD obtains CDPH approval for laboratory testing. 

Please also report:

  • Any person whose death certificate lists acute flaccid myelitis as a cause of death or a condition contributing to death.
  • Autopsy findings that include histopathologic evidence of inflammation involving the anterior horn of the spinal cord spanning ≥1 vertebral segment.

Contact CDPH at 510-620-3737 for assistance with reporting or request for clinical consultation.

Specimen Collection and Submittal

Collect specimens for suspect cases as early as possible in the course of illness, preferably on the day of limb weakness onset, to increase the chance of virus detection. Please work with your LHD to submit specimens to CDPH VRDL to hold while the LHD obtains CDPH approval for laboratory testing. Clinicians should electronically complete a General Purpose Specimen Submittal Form (PDF) for each individual specimen and include printed copies when shipping to CDPH VRDL.

Please collect and submit to VRDL all 5 of the following specimens:

  1. Nasopharyngeal swab in viral transport media, or nasopharyngeal wash or aspirate (in sterile collection tube)
  2. Oropharyngeal swab in viral transport media
  3. CSF (2-3cc, if available, in sterile collection tube)
  4. Serum (acute and convalescent), collected prior to treatment with IVIG, (2-3 cc in red or tiger-top tube)
  5. Two stool specimens (two quarter-sized amounts in a sterile wide-mouth container) collected 24 hours apart

Samples may be sent on dry ice or cold pack for delivery Tuesday through Friday to:

ATTN: Specimen Receiving
850 Marina Bay Parkway

Richmond, CA 94804

For questions about specimen submittal or shipping to CDPH VRDL call: 510-307-8585.


Specimen Testing

VRDL will perform molecular testing for SARS-CoV-2, enterovirus, rhinovirus, and adenovirus. VRDL will also perform serologic testing for West Nile virus (during transmission season May-December), St. Louis encephalitis virus (SLEV) (in counties with SLEV environmental detection), and Zika, Dengue, and Chikungunya viruses (if indicated by travel history). Additional testing will also include metagenomics, host biomarker analysis, pathogen discovery and comprehensive antibody testing.  Results from these tests should not inform clinical management of patient because results may not be available in real-time.


Infection control precautions for suspected AFM cases

The CDC recommends standard, contact and droplet precautions for suspected or confirmed AFM cases.

CDC/CSTE AFM Case Definition and Classification

The CSTE AFM case definition will be used to assign a CDC case classification after review by a team of neurologists at CDC. The case classification should not be used to decide whether to report a patient. CDC's case classification is not meant to override a clinician's diagnosis, or the patient's treatment and rehabilitation plan. For more information visit the CDC Acute Flaccid Myelitis case definition and classification website. 

*Low muscle tone, limp, hanging loosely, not spastic or contracted.  


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