Longitudinal molecular epidemiology of human adenovirus in pediatric respiratory infections: a 12-year study in Korea (2008-2019).

Human adenovirus (HAdV) is a leading cause of respiratory infections, with clinical manifestations and disease severity varying by type. In this study, we analyzed HAdV types in South Korea over a 12-year period before the COVID-19 pandemic. From January 2008 to December 2019, HAdV isolates were prospectively collected from children with suspected respiratory infections at a single tertiary center. HAdV typing was performed through sequence analysis of hexon gene hypervariable regions (HVRs) 1-6. Among 350 HAdV isolates, members of four species (A, B, C, and E) and 10 types (1-6, 31, 34, 35, and 55) were identified. Overall, HAdV-3 was most prevalent (49.4%), followed by HAdV-2 (19.1%), HAdV-1 (14.6%), and HAdV-4 (6.6%). HAdV-3 caused four recurrent outbreaks at intervals of 3 to 4 years without significant genetic changes in the hexon HVRs. HAdV species C (types 1, 2, 5, and 6) was detected endemically throughout the study period. Notably, HAdV-55, which was associated with fatal cases in military recruits in South Korea during 2017-2018, appeared in pediatric cases. HAdV epidemiology studies are important for providing clinical data on circulating HAdVs in children, and there is a need for ongoing surveillance and research.