Clinical and molecular epidemiology of human bocavirus in respiratory and fecal samples from children in Hong Kong

Abstract

Background: Human bocavirus (HBoV) is a recently discovered parvovirus associated with respiratory tract infections in children. We conducted the first systematic prospective clinical and molecular study using nasopharyngeal aspirates (NPAs) and fecal samples.

Methods: NPAs negative for influenza virus, parainfluenza virus, respiratory syncytial virus, adenovirus, and coronavirus and fecal samples from patients with acute gastroenteritis were included. On the basis of results from a pilot study using 400 NPAs from all age groups, a prospective 12-month study was conducted to detect HBoV in 1,200 NPAs and 1,435 fecal samples from patients <18 years old by polymerase chain reaction. The complete genome sequences of HBoVs from 12 NPAs and 12 fecal samples were determined.

Results: Of the 400 NPAs collected in the pilot study, 20 (5.0%) were found to contain HBoV, all from children <5 years old. In the subsequent prospective study of pediatric patients, HBoV was detected in 83 (6.9%) of 1,200 NPAs. Upper and lower respiratory tract infections were equally common. HBoV was detected in 30 (2.1%) of 1,435 fecal samples. Fever and watery diarrhea were the most common symptoms. The seasonality of HBoV in NPAs and fecal samples was similar. Codetection with other pathogens occurred in 33% and 56% of NPAs and fecal samples, respectively, from patients with HBoV infection. Genomes of HBoVs from NPAs and fecal samples displayed minimal sequence variations.

Conclusions: HBoV was detected in fecal specimens in children with acute gastroenteritis. A single lineage of HBoV was associated with both respiratory tract and enteric infections.

Figure 1.

Seasonality of human bocavirus (HBoV) in nasopharyngeal aspirates (NPAs) and fecal samples (A) and distribution of HBoV-positive children by age (B).

Table 1.

Clinical characteristics of the patients with human bocavirus (HBoV) detected in nasopharyngeal aspirates.

Table 2.

Summary of characteristics of the patients with human bocavirus detected in fecal samples.

Table 3.

Clinical characteristics of the 25 patients with human bocavirus detected in fecal samples.

Figure 2.

Phylogenetic trees of complete NS1, NP1, and VP1/VP2 gene sequences of 12 human bocavirus (HBoV) strains from nasopharyngeal aspirates (NPAs) and 12 HBoV strains from fecal samples. The trees were inferred from NS1 (A), NP1 (B), and VP1/VP2 (C) gene data by the neighbor-joining method, using bootstrap values calculated from 1000 trees. The trees were rooted using the NS1, NP1, and VP1/VP2 gene sequences of minute virus of canine; 1920 nucleotide positions in each NS1 gene, 660 nucleotide positions in each NP1 gene, and 2016 nucleotide positions in each VP1/VP2 gene were included in the analysis. The scale bar indicates the estimated no. of substitutions per 500 bases by Kimura's 2-parameter model. HBoV strains ST1 and ST2, from Sweden, were the 2 prototype strains. Strains WLL-1 and CZ643 are from China, and strain CRD2 is from the United States.