Epidemiological characteristics and genetic evolution of human bocavirus infection in hospitalized children with severe acute respiratory infection in Hangzhou

Abstract

Objective To study the epidemiological characteristics and genetic evolution of human bocavirus (HBoV) infection in hospitalized children with severe acute respiratory infection (SARI) in Hangzhou. Methods A total of 1 388 clinical specimens were collected from children with SARI admitted in Affiliated Children’s Hospital, Zhejiang University School of Medicine from January 2011 to December 2014. HBoV1-4 and other respiratory pathogens were identified by fluorescent real-time polymerase chain reaction (fRT-PCR). The VP1 gene in HBoV1 positive samples was amplified and sequenced for genetic analysis with Clustal X and MEGA 6.0. Chi-square test and Fisher exact probability were used to analyze the data. Results Eighty five HBoV positive samples were detected from 1 388 samples (6.12%), among which 83 (97.65%) were HBoV1 positive and 2 (2.35%) were HBoV2 positive. The positive rates of HBoV in males and females were 6.54% and 5.35% (χ2=0.780, P>0.05). The posititve detection rate of HBoV in all age groups was statistically significant (χ2=47.446, P 3 years was lowest (1.64%), in children aged ≤6 months and aged 1-3 years was 3.04% and 3.33%, respectively. The detection rate of HBoV in summer was the highest (14.97%), followed by that in autumn (7.14%), spring (3.19%) and winter (1.97%) (χ2=58.807, P 0.05). The co-infection rate with other respiratory pathogens was 62.35%. The main pathogens were human rhinovirus (33.96%), parainfluenza virus (28.30%) and respiratory syncytial virus (20.75%). The incidence of anhelation and wheezing in HBoV positive group was higher than that in HBoV negative group (χ2=15.161 and 13.914, P<0.01). Sequence analysis of VP1 gene showed that 44 isolates belonged to the same branch (clade 1) as Swedish strain ST2, and 2 isolates HZ12-S32 and HZ12-S199 belonged to a separated branch. Conclusion HBoV is an important causative agent of hospitalized children with SARI in Hangzhou area and has high co-infection with other respiratory pathogens. Most of the strains belong to the same clade as the Swedish strain ST2, and two strains of HZ12-S32 and HZ12-S199 are identified in a separated clade. Key words: Human bocavirus; Severe acute respiratory infection; Epidemiology; Genetic evolution