Human bocavirus 2 (HBoV2) is a small, non-enveloped single-stranded DNA virus in the family Parvoviridae and genus Bocaparvovirus. It was discovered in 2009 in stool samples and is mainly associated with gastrointestinal infections in children.
Explanation
HBoV2 is one of four recognized human bocavirus species. Its genome is about 5.3 kilobases long and encodes nonstructural proteins and a capsid protein. The virus shares sequence homology with bovine and canine bocaviruses, but phylogenetic analysis distinguishes HBoV2 from the other human bocavirus species. Molecular studies show that HBoV2 uses a linear, negative-sense DNA genome with terminal hairpin structures typical of parvoviruses. Epidemiological surveys have detected HBoV2 worldwide, mostly in fecal samples from young children with acute gastroenteritis, and less often in respiratory specimens. Seroprevalence studies indicate that exposure occurs early in childhood, although rates are lower than those reported for HBoV1. HBoV2 often coexists with other pathogens, and its role as a primary etiological agent remains under investigation. Experimental work is limited by the absence of a robust cell culture system or animal model, but evidence of viremia and virus shedding in stool suggests systemic spread following respiratory or fecal-oral transmission. The virus appears to persist in lymphoid tissues and may establish latent or persistent infection.
Clinical and Epidemiologic Notes
Small-scale studies in Pakistan and Australia first isolated HBoV2 from stool samples of children with acute flaccid paralysis and gastroenteritis. Subsequent surveys in Europe, Asia and Africa have reported detection rates ranging from 0.5% to 5% of cases of diarrhea. HBoV2 DNA has also been found in respiratory secretions, but at much lower frequencies. Co-infection with other viruses such as rotavirus, norovirus and adenovirus is common, making it difficult to assign causality. Some sequence variants appear to result from recombination with HBoV3. Sequence analysis shows limited diversity among isolates, with high nucleotide identity across continents. Because the virus has not yet been successfully propagated in cell culture, diagnosis relies on polymerase chain reaction assays targeting conserved genomic regions. HBoV2 is a distinct member of the bocaparvovirus group that is mainly detected in human fecal samples. Although its genome and epidemiology are increasingly understood, its contribution to disease remains uncertain because infections are commonly concurrent with other pathogens. Improved surveillance and development of culture systems are needed to clarify its role. Related Terms: Human Bocavirus 1, Human Bocavirus 3, Human Bocavirus 4, Parvovirus 4 (PARV4), Bocaparvovirus