Respiratory Syncytial Virus Disease Severity in Young Children.

BACKGROUND: Respiratory syncytial virus (RSV) is the leading cause of acute respiratory infections (ARIs) in hospitalized children. Although prematurity and underlying medical conditions are known risk factors, most of these children are healthy, and factors including RSV load and subgroups may contribute to severity. Therefore, we aimed to evaluate the role of RSV in ARI severity and determine factors associated with increased RSV-ARI severity in young children. METHODS: Children aged <5 years with fever and/or ARI symptoms were recruited from the emergency department (ED) or inpatient settings at Vanderbilt Children's Hospital. Nasal and/or throat swabs were tested using quantitative reverse-transcription polymerase chain reaction for common respiratory viruses, including RSV. A severity score was calculated for RSV-positive children. RESULTS: From November 2015 through July 2016, 898 participants were enrolled, and 681 (76%) had at least 1 virus detected, with 191 (28%) testing positive for RSV. RSV-positive children were more likely to be hospitalized, require intensive care unit admission, and receive oxygen compared with children positive for other viruses. Higher viral load, White race, younger age, and higher severity score were independently associated with hospitalization in RSV-positive children. No differences in disease severity were noted between RSV A and RSV B. CONCLUSIONS: RSV was associated with increased ARI severity in young children enrolled from the ED and inpatient settings, but no differences in disease severity were noted between RSV A and RSV B. These findings emphasize the need for antiviral therapy and/or preventive measures such as vaccines against RSV in young children.