Acute Flaccid Myelitis in the United States, August-December 2014: Results of Nationwide Surveillance

Abstract

Background: During late summer/fall 2014, pediatric cases of acute flaccid myelitis (AFM) occurred in the United States, coincident with a national outbreak of enterovirus D68 (EV-D68)-associated severe respiratory illness.

Methods: Clinicians and health departments reported standardized clinical, epidemiologic, and radiologic information on AFM cases to the Centers for Disease Control and Prevention (CDC), and submitted biological samples for testing. Cases were ≤21 years old, with acute onset of limb weakness 1 August-31 December 2014 and spinal magnetic resonance imaging (MRI) showing lesions predominantly restricted to gray matter.

Results: From August through December 2014, 120 AFM cases were reported from 34 states. Median age was 7.1 years (interquartile range, 4.8-12.1 years); 59% were male. Most experienced respiratory (81%) or febrile (64%) illness before limb weakness onset. MRI abnormalities were predominantly in the cervical spinal cord (103/118). All but 1 case was hospitalized; none died. Cerebrospinal fluid (CSF) pleocytosis (>5 white blood cells/µL) was common (81%). At CDC, 1 CSF specimen was positive for EV-D68 and Epstein-Barr virus by real-time polymerase chain reaction, although the specimen had >3000 red blood cells/µL. The most common virus detected in upper respiratory tract specimens was EV-D68 (from 20%, and 47% with specimen collected ≤7 days from respiratory illness/fever onset). Continued surveillance in 2015 identified 16 AFM cases reported from 13 states.

Conclusions: Epidemiologic data suggest this AFM cluster was likely associated with the large outbreak of EV-D68-associated respiratory illness, although direct laboratory evidence linking AFM with EV-D68 remains inconclusive. Continued surveillance will help define the incidence, epidemiology, and etiology of AFM.

Keywords: acute flaccid myelitis; enterovirus; limb weakness; polio; surveillance.

Figure 1

Number of acute flaccid myelitis (AFM) cases by week of limb weakness onset (A), dyspnea visits at hospital emergency departments among children aged <18 years (B), and respiratory specimens tested for enterovirus D68 (EV-D68) at the Centers for Disease Control and Prevention (CDC) by week of sample collection (C), United States, 1 June–31 December 2014. B, BioSense data are combined from 24 states that reported at least 1 AFM case and whose BioSense data (>90% of emergency department visits) came from hospitals that contributed consistently during August–October 2014. BioSense hospitals may be different from the hospitals that reported AFM cases. C, First public health communication informing states that CDC was available to test respiratory specimens for EV-D68 was on 28 August 2014. On 25 September 2014, CDC communications stated that CDC testing would be prioritized to samples from children with severe respiratory disease. Over time, more state laboratories developed capacity to test their samples.

Figure 2

State distribution of acute flaccid myelitis (AFM) cases, United States, August–December 2014 (N = 120).