Viral Etiology of Acute Lower Respiratory Tract Infections in Hospitalized Children in Nagasaki, a Regional City of Japan in 2013-2015.

BACKGROUND: Acute lower respiratory tract infections (ALRIs) are the most common disease for hospitalized children in Japan. The aim of this study was to identify viruses in children hospitalized for ALRIs and to demonstrate epidemiologic and clinical characteristics in Japan. METHODS: During a 2-year period from February 2013 to January 2015, we collected nasopharyngeal swab specimens from almost all hospitalized children with ALRIs in Nagasaki, a regional city of Japan, and its environs. Viruses were detected by multiplex polymerase chain reaction from these samples. RESULTS: We detected one or more viruses from 259 (69%) of 374 patients, 227 of whom were infected with a single virus, 30 with 2, and 2 with 3 viruses. Detected viruses in this study were rhinovirus (46.4%), respiratory syncytial virus (29.7%), human metapneumovirus (6.8%), parainfluenza virus (5.5%), enterovirus D68 (3.4%), influenza virus (2.7%), adenovirus (2.4%), bocavirus (2.0%) and Coxsackie virus (1.0%). We detected a seasonal shift in respiratory syncytial virus outbreaks from the 2013-2014 to the 2014-2015 seasons. There was no significant difference in clinical course and severity among those viruses. Patients with a history of asthma or underlying diseases were older and more frequently required oxygen therapy than previously healthy patients. CONCLUSIONS: Viral etiology in hospitalized children with ALRIs in Nagasaki, Japan, was similar to that in many other countries. Enterovirus D68, which was recently recognized as a causative agent of severe ALRIs, was also identified in this study area. Severity of ALRIs may depend on underlying disease rather than type of etiologic virus.

Does respiratory virus coinfection increases the clinical severity of acute respiratory infection among children infected with respiratory syncytial virus?

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infection in children less than 5 years of age. The impact of non-RSV respiratory virus coinfection on the severity of RSV disease is unknown. METHODS: This hospital-based prospective study was conducted in Nagasaki, Japan, on all children less than 5 years of age with acute respiratory infection (ARI) who had undergone a rapid RSV diagnostic test between April 2009 and March 2010. Thirteen respiratory viruses were identified from nasopharyngeal swab samples using a multiplex polymerase chain reaction; polymerase chain reaction-positive samples were considered as confirmed respiratory virus infections. The cases were classified into 3 categories (pneumonia, moderate-to-severe nonpneumonic ARI and mild ARI) according to the findings of the chest radiograph and the hospitalization records. RESULTS: Among 384 cases enrolled, 371 were eligible for analysis, of whom 85 (23%) were classified as pneumonia cases; 137 (37%) as moderate-to-severe nonpneumonic ARI cases and 162 (40%) as mild ARI cases. RSV was detected in 172 cases (61.6%), and 31 cases (18.0%) had double or triple infections with other respiratory viruses. RSV infection was more frequently observed in pneumonia cases (odds ratio [OR]: 2.3; 95% confidence interval [CI]: 1.31-3.9) and moderate-to-severe nonpneumonic ARI cases (OR: 2.95; 95% CI: 1.82-4.78) than in mild ARI cases. The association with moderate-to-severe nonpneumonic ARI cases was stronger with RSV/non-RSV respiratory virus coinfection (adjusted OR: 4.91; 95% CI: 1.9-12.7) than with RSV single infection (adjusted OR: 2.77; 95% CI: 1.64-4.7). CONCLUSIONS: Non-RSV respiratory virus coinfection is not uncommon in RSV-infected children and may increase the severity of RSV disease.