Human bocavirus infection in young children in the United States: molecular epidemiological profile and clinical characteristics of a newly emerging respiratory virus

Abstract

Background: Human bocavirus (HBoV) is a newly identified human parvovirus that was originally identified in the respiratory secretions of children with respiratory tract disease. To further investigate the epidemiological profile and clinical characteristics of HBoV infection, we screened infants and children <2 years of age (hereafter referred to as "children") for HBoV.

Methods: Children for whom respiratory specimens submitted to a diagnostic laboratory tested negative for respiratory syncytial virus, parainfluenza viruses (types 1-3), influenza A and B viruses, and adenovirus, as well as asymptomatic children, underwent screening for HBoV by use of polymerase chain reaction (PCR). Respiratory specimens were obtained from the children from 1 January 2004 through 31 December 2004.

Results: Twenty-two (5.2%) of the 425 children who had a respiratory specimen submitted to the diagnostic laboratory and 0 of the 96 asymptomatic children were found to be positive for HBoV by PCR (P=.02). Fever, rhinorrhea, cough, and wheezing were observed in > or =50% of the HBoV-positive children. Of the 17 children who had chest radiography performed, 12 (70.6%) had abnormal findings. HBoV appeared to have a seasonal distribution. Nucleotide polymorphisms were detected in the viral capsid protein (VP) 1/VP2 genes. Two distinct HBoV genotypes circulated during the study period.

Conclusions: HBoV is circulating in the United States and is associated with both upper and lower respiratory tract disease in infants and young children.

Figure 1

Distribution of human bocavirus (HBoV)–positive specimens in 2004, by month. The no. of respiratory specimens submitted to the Clinical Virology Laboratory at Yale–New Haven Hospital (New Haven, Connecticut) (white bars) the no. of HBoV-positive specimens (black bars), and the percentage of HBoV-positive specimens collected in each month are shown

Figure 2

Distribution of human bocavirus–positive children, by age

Table 1

Clinical characteristics associated with human bocavirus (HBoV) infection in children <2 years of age

Figure 3

A Map of the human bocavirus (HBoV) genome. The putative open reading frames of the HBoV genome are shown above the map. A portion of the NP-1 gene (white box) was targeted during screening for HBoV in respiratory specimens. Phylogenetic analysis was based on sequences of the 3′ third of the viral capsid protein (VP) 1/VP2 genes (nt 4370–5189 of the HBoV genome) (black box). B Phylogenetic analysis of HBoV isolates. The sequences of the New Haven (NH) isolates, the patient nos., and the month of acquisition of each HBoV-positive specimen (month/year) are shown. HBoV isolates recovered from 2 children with nosocomial infection whose respiratory specimens were collected 4 days apart are denoted by arrows. &cirf;, Initial strains of HBoV (ST1 and ST2) identified by Allander et al. [5]; ▴, HBoV isolate from St Louis, Missouri (CRD2). For figure clarity, not all New Haven isolates were included in the phylogenetic analysis. The HBoV sequences that were omitted were identical to at least one of the strains shown in the figure