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BACKGROUND: In September 2014, the Colorado Department of Public Health and Environment reported nine children with acute flaccid myelitis (AFM). All had spinal magnetic resonance imaging (MRI) with predominantly gray matter abnormalities. The majority reported a respiratory or febrile prodrome, and all occurred amidst a nationwide outbreak of severe respiratory illness caused by enterovirus D-68 (EV-D68). CDC subsequently issued a health advisory requesting national case reporting.
METHODS: Cases were defined as acute onset focal limb weakness in persons ≤21 years occurring on or after August 1, 2014 with predominant gray matter lesions on spinal MRI. State health departments reported suspected cases using standardized forms. Cases were confirmed by one of two CDC neurologists. Specimens were submitted to CDC for testing.
RESULTS: As of December 2014, 34 states reported 102 cases. Fifty-eight (57%) case-patients had onset of weakness in September. Median age was 7 years (range, 5 months‒20 years); 62 (61%) were male and 100 (99%) were hospitalized. At time of report, cases have been followed a median of 18 days (range, 2‒101 days) after weakness onset. Of 88 cases with information available, 56 (64%) partially improved, 31 (35%) did not improve, 1 (1%) recovered. No fatalities were reported. In addition to limb weakness, 30 (29%) cases had cranial nerve dysfunction, 6 (6%) had altered mental status, 4 (4%) had seizures. Ninety-one (89%) reported a preceding respiratory illness and 66 (65%) a febrile illness. Of 44 cases with CSF specimens tested, 1 (2%) was positive for both EV-D68 and Epstein-Barr virus by real-time RT-PCR, and was noted to have 1500 red blood cells. CSF testing for adenovirus, herpesviruses, arboviruses, and all other enteroviruses, including poliovirus, in all cases was negative. Of 46 cases with respiratory specimens collected within two weeks of weakness onset, 8 (17%) were positive for EV-D68, 6 (13%) for various rhinoviruses, and 1 (2%) for enterovirus 71 (EV-71). Stool specimens were received from 46 cases, of which 2 (4%) were positive for coxsackievirus, 1 (2%) for EV-71, 4 (9%) for various rhinoviruses, 6 (13%) for adenovirus and none for poliovirus.
CONCLUSIONS: We identified >100 AFM cases occurring over 4.5 months, coincident with a national EV-D68 respiratory disease outbreak. No single etiology has been identified. Although one CSF specimen tested positive for EV-D68, presence of blood in CSF complicates interpretation of this result. Further investigations are needed to quantify incidence and define etiologies of AFM in the United States.