An Outbreak of Human Adenovirus Infection Among Children Post COVID‐19 Pandemic in Southern China

Abstract

Human adenovirus (HAdV) is an important pathogen causing pediatric acute respiratory illness (ARI) before COVID‐19 pandemic. Since January 2023, China has reported ARI outbreaks attributed to Mycoplasma pneumoniae and other respiratory viruses. In this study, a total of 276 737 pediatric patients with ARI were enrolled from January 2023 to April 2024. HAdV‐positive samples were identified by real‐time PCR. The monthly frequency of HAdV infection remained below 0.9% through July 2023, with a gradual rise to 1.03% in November and 2.92% in December. A significant surge was observed in the early months of 2024, with HAdV‐positive rate spiking to 10.81% (3025/27992) in January and 10.75% (1393/12954) in February. The adenovirus outbreak peaked during the third to fifth week of 2024, with the highest recorded ratio of 23.86% (131/549) on January 29, 2024. Among the 600 samples that were typed, the predominant subtypes were HAdV‐B3 (96%) and HAdV‐C1 (2.67%). Phylogenetic analysis of two HAdV‐B3 strains revealed close genomic similarity to the strain BJ20170281, which was isolated in Beijing, China, in 2017. HAdV‐B3 has triggered an outbreak in Southern China in winter, an atypical epidemic season, following the COVID‐19 pandemic. Ongoing surveillance of circulating pathogens including HAdV is necessary to prevent ARI outbreaks.