Human bocavirus (HBoVs) is an emerging virus globally, and its prevalence, diversity, and evolution in children with acute gastroenteritis require further study. Fecal specimens collected from outpatients with acute gastroenteritis in Beijing, China, from April 2014 to December 2023, were tested for HBoVs by PCR targeting the NS1 gene. Genotyping was based on the NP1/VP1 boundary region, and nearly full-length HBoV2 sequences were analyzed phylogenetically. A total of 79 HBoVs-positive specimens (2.5%, 79/3,116, 95% CI: 2.0%–3.1%) were detected, with HBoV2 (65.8%, 52/79, 95% CI: 55.4%–76.3%) as the dominant genotype, followed by HBoV1 (25.3%, 20/79, 95% CI: 15.7%–34.9%) and HBoV3 (8.9%, 7/79, 95% CI: 2.6%–15.1%). HBoVs were distributed throughout the year, with higher positive rates observed from August to December 2018–2021. They predominantly infected children younger than 5 years, especially those aged 6–24 months (3.3%, 52/1,591, 95% CI: 2.4%–4.1%). HBoV2C was the prevalent sub-genotype in Beijing. Novel recombination events were detected between HBoV2 sub-genotypes, with breakpoints in the NS1 and VP3 gene regions. Evolutionary analysis estimated the time to the most recent common ancestor (tMRCA) for HBoV2 dating back to 1845, with a mean nucleotide substitution rate of 1.4 × 10 ⁻⁴ substitutions/site/year, and that HBoV2A evolved faster than HBoV2C. The evolutionary rates decreased in the following order: NP1, VP3, VP1, and NS1. A purifying selection was observed on HBoV2 genes, with one positively selected site in the NS1 gene. In conclusion, HBoV2 was the dominant genotype in children with acute gastroenteritis in Beijing, China, with higher susceptibility in those under 2 years old. Novel recombination events between HBoV2 sub-genotypes occurred frequently. IMPORTANCE: Acute gastroenteritis remains a leading cause of morbidity and mortality in children, with viral infections being the primary causative agents. In this study, we investigated the prevalence of human bocavirus (HBoVs) in children with acute gastroenteritis in Beijing from 2014 to 2023, identifying HBoV2C as the predominant sub-genotype. Additionally, this study reported the first estimate of the evolutionary rate for global HBoV2 (1.4 × 10 ⁻⁴ substitutions/site/year) and identified novel intra-genotype recombination events in HBoV2. The results not only filled a gap in the evolutionary studies of global HBoV2 but also offered valuable data for the development of effective surveillance and prevention strategies for controlling acute gastroenteritis in children.

Human Bocavirus 1 (HBoV1) is one major pathogen that has been associated with wheezing illnesses. However, there is still a lack of effective clinical predictive indicators for wheezing illnesses in children infected with HBoV1. A retrospective cohort study was conducted among pediatric patients with single-HBoV1 infection from September 2016 to August 2023. Then, univariate logistic regression was used to screen potential predictors for wheezing illness, and Least Absolute Shrinkage and Selection Operator (LASSO) regression was applied to minimize overfitting and select key predictors. Finally, a multivariate logistic regression model was constructed in a training dataset comprising 80% of patients and validated in an independent test dataset comprising 20% of patients. Then, its performance was evaluated using the Area Under the Curve (AUC). A total of 330 pediatric patients were enrolled, including 228 in the wheezing-illness group and 102 in the non-wheezing group. Three independent predictors, including abnormal NK cell percentage (OR = 1.101, 95 %CI 1.03–1.27), preterm birth (OR = 1.65, 95 %CI 1.49–1.82) and personal history of allergy (OR = 1.25, 95 %CI 1.11–1.41), were identified. The model achieved AUCs of 0.904 and 0.876 in the training and test sets, respectively. Using a Youden-derived threshold (0.382), the high-risk group in the test set had an observed wheezing rate of 85.3%, compared with 18.7% in the low-risk group (p < 0.001). Calibration was satisfactory (Hosmer–Lemeshow p = 0.324 and 0.576). A validated predictive model incorporating abnormal NK cell percentage, preterm birth and personal history of allergy accurately stratifies the risk of wheezing illness after HBoV1 infection in children, facilitating early clinical intervention.

It has been reported that chronic infection of human norovirus (HuNoV) may potentially serve as a reservoir for viral variants with the possibility to evade population immunity or alter the binding sites of HBGA receptors. In this study, a child diagnosed with Burkitt lymphoma and positive for HuNoV determined by real-time PCR (qPCR) firstly in 15 August 2016, was followed up until 20 March 2018, and 26 fecal specimens and one vomitus were collected to trace the evolutionary characteristics of HuNoV by phylogenetic analysis, meta-genomics next-generation sequencing (mNGS), and temporal evolutionary analysis of VP1 among 23 specimens positive for HuNoV. There were 15 specimens with partial RdRp gene sequences forming an independent cluster with sequences of GII.P31, 14 with the region C sequences and 11 with P domain sequences of VP1 gene clustered together with HuNoV GII.4 Sydney_2012. All these sequences showed that mutations accumulated nearly in a time order, and more mutations were shown in the key epitopes A–E or near the binding sites for HBGA in subdomain P2 with higher evolutionary rates. Analysis of NGS data identified intra-host viral quasi-species, and two genome sequences of the same length from mNGS were assembled from N705, with mutations located in the region of subdomain P2 (1171 nt–1202 nt) which led to five amino acid mutations. In conclusion, the accumulated mutations of HuNoV, especially in subdomain P2, were explored in a child with Burkitt lymphoma, and the sequencing of HuNoV from immunocompromised individuals was proven critical for monitoring intra-host quasi-species evolution and potential variant emergence, providing basic data for clinical infection control.