BACKGROUND: Standardized surveillance for acute flaccid myelitis (AFM) was adopted by the Council of State and Territorial Epidemiologists in June 2015 following an increase in cases during 2014, to determine baseline information for AFM and help identify an etiology.
METHODS: Confirmed cases of AFM are defined as patients with acute onset of focal limb weakness and an MRI showing a spinal cord lesion largely restricted to gray matter spanning one or more vertebral segments. State health departments report suspected cases using standardized forms. Cases are reviewed and confirmed as meeting the case definition at CDC. Specimens were submitted to CDC for enterovirus (EV) and parechovirus testing. Descriptive analyses of confirmed cases are presented.
RESULTS: From January 1 through October 31, 2016, a total of 108 confirmed cases were reported to CDC from 36 states; 70% of cases had onset of limb weakness between August and October. Median age of confirmed cases was 5.0 years (range, 5 months‒61 years); 63 (58%) were male and all were hospitalized. No fatalities were reported. Forty-one (38%) cases reported limb weakness in all four extremities and 84/104 (81%) cases with CSF drawn had pleocytosis (white blood cell count >5 cells/mm3). Among those with reported information, other clinical findings included: cranial nerve dysfunction (31%), altered mental status (22%), seizures (2%), and requirement of mechanical ventilation (32%). Ninety (83%) reported a preceding respiratory or febrile illness in the four weeks before weakness. Testing performed at CDC identified the following: of 55 cases for which CSF specimens were submitted, none were positive for EV or parechoviruses; of 43 cases with respiratory specimens collected within two weeks of weakness onset, 12 (28%) were positive for EV-D68, 3 (7%) for various rhinovirus (RV; RV-A57, RV-A58, RV-B83), 2 (5%) for non-specified EV/RV, 1 (2%) for echovirus 6. Stool specimens were received from 45 cases, 1 (2%) was positive for EV-D68, 2 (4%) for coxsackievirus (CV; CV-A10, CV-B4), 1 (2%) for EV-A71, 2 (4%) for various RV (RV-A57, RV-B83), 2 (4%) for non-specified EV/RV, none for poliovirus.
CONCLUSIONS: From January through October, CDC confirmed 108 cases of AFM. Case counts peaked between August and September, a time frame similar to that observed in 2014. Pathogen-specific testing remains inconclusive; therefore, testing has shifted to explore other infectious and non-infectious causes, including immune-mediated mechanisms. Continued vigilance with surveillance and reporting of suspected cases remains an important tool for characterization and understanding of AFM.