CDC Issues Updated Data on Acute Flaccid Myelitis in US

November 21, 2018

By Marilynn Larkin

NEW YORK (Reuters Health) - So far this year in the U.S., there have been 106 confirmed cases of acute flaccid myelitis (AFM) in 29 states, representing about a threefold increase in such cases compared with the same period in 2017, according to the U.S. Centers for Disease Control and Prevention (CDC).

AFM is characterized by rapid onset of flaccid weakness in one or more limbs plus gray matter lesions in the spinal cord. (

In a press conference last week about AFM, Dr. Nancy Messonnier, director for the National Center for Immunizations and Respiratory Diseases, told reporters, "There are currently no targeted therapies or interventions with enough evidence to endorse or discover their use. We recommend clinicians expedite neurology and infectious disease consultations to discuss treatment and management considerations. As a mom, I know what it's like to be scared for your child, and I understand parents want answers. . . Right now the science doesn't give us an answer."

Pediatrician Dr. Manisha Patel, who is leading clinician outreach for the CDC's AFM investigation, told Reuters Health, "Clinicians should be vigilant for and immediately report to their state or local health department any patients who meet the clinical criteria for AFM (sudden onset of flaccid limb weakness) using CDC's patient summary form (, regardless of any laboratory results or MRI findings."

"They should also consult with their local and state health department for laboratory testing of stool, respiratory, sera, and cerebrospinal fluid specimens for enteroviruses (including poliovirus), West Nile virus, and other known infectious etiologies for patients who meet the AFM clinical criteria," she said by email.

"Collect specimens from patients under investigation for AFM as early as possible in the course of illness," she added, "preferably on the day of onset of limb weakness." (More on AFM specimen collection:

Further, she said, "refer to CDC's "Interim Considerations for Clinical Management of Patients with Acute Flaccid Myelitis," released in 2014 and updated in 2018. ( And consult with infectious diseases and neurology experts to assist with diagnostic and treatment recommendations."

Among confirmed cases identified from January 1-November 2, 2018, the median age was four years, 59% were male, and most were white, the CDC reported online November 13 in its Morbidity and Mortality Weekly Report.

During the four weeks preceding the onset of limb weakness, signs and symptoms consistent with a viral illness were reported for 99% of patients, including fever for 81%, respiratory symptoms (e.g., cough, congestion) for 78%, and gastrointestinal symptoms (e.g., vomiting and diarrhea) for 38%.

Upper limb only involvement was reported by 47.5% patients; lower limb only by 8.8%; two to three upper and lower limbs by 15%; and all four limbs by 28.8%.

All patients with confirmed AFM were hospitalized, with 59% admitted to intensive care units.

Among 98% of cases with CSF results, 83% had pleocytosis (median cell count, 103 cells per mm3) and most had a lymphocyte predominance.

Median CSF protein was 47 mg per dL (normal <45) and glucose, 59 mg per dL (normal 40 or greater).

The median interval from limb weakness to CSF collection was one day, and the median interval from sign or symptom onset to CSF collection was seven days for respiratory illness, four days for gastrointestinal symptoms, and three days for fever.

More than half (54%) of AFM patients tested positive for an enterovirus/rhinovirus. No deaths have been reported.

"Clinical, laboratory, and epidemiologic evidence to data suggest a viral association," Dr. Patel and colleagues state.

Infectious diseases specialist Dr. Christopher Ohl of Wake Forest Baptist Medical Center in Winston-Salem, North Carolina, affirms in an email to Reuters Health, "A preceding febrile viral illness in the majority of cases further suggests a viral infection as the cause."

"However," he noted, "many patients tested negative and further laboratory testing and epidemiologic investigation is needed. It could well be that there are more than one specific causes with similar disease pathology and thus similar symptoms and presentations."

Infectious Diseases Society of America spokesperson Dr. Amesh Adalja, a Senior Scholar at the Johns Hopkins University Center for Health Security, added by email, "Awareness of AFM is very high now as it has been in the headlines, and the aggressive outreach campaign by the CDC has clinicians across the country on alert to cases. Therefore, we can expect to find more cases."

"It's also important to remember that before 2014 AFM was not a reportable condition so it's unclear what the true baseline case incidence is," he noted.

Dr. Patel confirms that investigations into AFM are ongoing.


MMWR 2018.