Bocavirus infection in otherwise healthy children with respiratory disease

To evaluate the role of human bocavirus (hBoV) as a causative agent of respiratory disease, the importance of the viral load in respiratory disease type and severity and the pathogenicity of the different hBoV species, we studied all hBoV-positive nasopharyngeal samples collected from children who attended an emergency room for a respiratory tract infection during three winters (2009-2010, 2011-2012, and 2013-2014). Human bocavirus was detected using the respiratory virus panel fast assay and real-time PCR. Of the 1,823 nasopharyngeal samples, 104 (5.7%) were positive for hBoV; a similar prevalence was observed in all three periods studied. Among hBoV-infected children, 53.8% were between 1-2 years old, and hBoV was detected alone in 57/104 (54.8%) cases. All of the detected hBoV strains belonged to genotype 1. The median hBoV load was significantly higher in samples containing strains with both the N546H and T590S mutations compared to other samples (p<0.05). Children with a single hBoV-1 infection more frequently had upper respiratory tract infections (URTIs) than those who were co-infected (37.0% vs 17.8%, respectively, p = 0.04). The duration of hospitalization was longer among children with high viral loads than that observed among children with low viral loads (8.0 ±2.2 days vs 5.0 ±1.5 days, respectively, p = 0.03), and the use of aerosol therapy was more frequent among children with high viral loads than among those with low viral loads (77.1% vs 55.7%, respectively, p = 0.04). This study shows that hBoV is a relatively uncommon but stable infectious agent in children and that hBoV1 seems to be the only strain detected in Italy in respiratory samples. From a clinical point of view, hBoV1 seems to have in the majority of healthy children relatively low clinical relevance. Moreover, the viral load influences only the duration of hospitalization and the use of aerosol therapy without any association with the site of the respiratory disease.