BACKGROUND: The Enterovirus genus is comprised of 4 human enterovirus (EV, A–D) and 3 rhinovirus (RV, A-C) species with hundreds of distinct types. The epidemiology and clinical features of respiratory Enterovirus infections have not been fully described. In 2014, an unexpected increase in hospitalizations and ICU admissions due to respiratory illness occurred in the United States. Although EV-D68 was the predominant pathogen associated with this increase, numerous other RVs and EVs were detected.
METHODS: EV/RV-positive respiratory specimens collected at hospitals and health departments throughout the US during August 1st - November 30th were submitted to CDC for additional testing. Case report forms including basic clinical and epidemiologic data were also submitted. Specimens confirmed EV/RV-positive were subjected to partial VP2/VP4 or partial VP1 sequencing to identify specific EV and RV types. Clinical and epidemiologic characteristics of EV-D68-, RV-A-, RV-B- and RV-C-positive cases were assessed and grouped for comparisons when similar.
RESULTS: Among 1,111 specimens from hospitalized patients, 537 (48%) were EV-D68-positive, 378 (34%) were RV-positive (RV-A=165, RV-B=46, RV-C=167), 26 (2%) had another EV detected, and 128 (12%) had no RV or EV detected; the virus types of 42 (4%) specimens are currently pending. At least 88 different RV types were identified, and the 5 most commonly detected were C40 (5.3%), C30 (4.5%), A29 (4.0%), C6 (4.0%), and C43 (4.0%). Thirteen different EV types were identified. Compared to RV-positive cases, EV-D68-positive cases were more likely to be children aged 1-17 years rather than infants or adults (54% vs 86%, p<0.0001), and, although ICU admission rates were similar, RV-positive cases were more likely to require intubation (18% versus 7%, p<0.0001). On average, wheezing, tachypnea and retractions were more common among EV-D68-positive and RV-C-positive cases (combined) (63%, 46%, and 40%, respectively) than among RV-A-positive and RV-B-positive cases (combined) (38%, 29% and 17%, respectively; all p-values <0.001). A history of asthma/reactive airway disease was more commonly reported among EV-D68/RV-C-positive cases than RV-A/B-positive cases (48% vs 35%, p<0.001), although RV-A/B-positive cases were more likely to report co-morbidities overall (88% vs 79%, p=0.004).
CONCLUSIONS: We provide a clinical and epidemiologic description of RVs and EV-D68 detected during a nationwide outbreak of respiratory viral illness. Patients with EV-D68 and RV-C infections exhibited similar co-morbidities and symptoms as compared with RV-A and RV-B infections. A better understanding of the epidemiology of co-circulating RV and EV could help guide clinical decisions and hospital preparedness during summer/fall respiratory seasons.