The prevalence and genetic characteristics of human bocavirus in patients with acute respiratory infection in China during 2012-2021.

Human bocavirus (HBoV) is a common respiratory virus among patients with acute respiratory infection (ARI). To investigate the prevalence and genetic characteristics of HBoV, clinical specimens from 13,109 ARI patients were collected through active surveillance from 12 provinces of China during 2012-2021. Extracted nucleic acid was screened and the viral protein 1 (VP1) gene was directly amplified and sequenced in HBoV-positive specimens. 3.51 % of patients were HBoV-positive, with children under 5 years old accounting for 93.48 % of cases. HBoV detection rate increased from 2.35 % in 2012-2019 to 5.38 % in 2020 and 7.68 % in 2021, with a pronounced increase in children aged 2-4 years and in Southern China. The age group with the highest detection rate shifted from infants under 2 years in 2012-2019 to children aged 2-4 years in 2020-2021. The proportion of HBoV co-detections increased significantly in 2020-2021, from 43.98 % to over 60.00 %. All HBoV cases were identified as HBoV-1 with 165 full length sequences of VP1 gene obtained. No temporal or geographic clustering was observed. The VP1 gene evolved at a rate of 7.99 × 10 substitutions/site per year, with ω-value less than 1, indicating that the VP1 protein was under negative selection pressure. Multiple antigen-associated amino acid mutations and positive selection sites were found in the VP1 protein. In conclusion, HBoV1 remains a major cause of pediatric ARI in China, but its epidemic pattern exhibited dynamic shifts during the coronavirus disease 2019 pandemic, while the viral genetic evolution remained relatively stable.