Seroepidemilogical investigations of healthy populations may be more useful than patient studies in assessing the prevalence, spread, and exposure distribution of HBoVs in the population. The seroprevalence data also allow a comparison between the frequency of natural infection and the frequency of this virus in individuals with infections [30] . However, previous seroepidemiological studies of HBoVs have mainly focused on HBoV1. HBoV1 specific IgG antibodies were frequently detected in children, with a seropositive rate ranging from 40.7%-60% for children , four years old and up to .85% for those $ four years old [19] . The seropositive rate of HBoV1 VP2-specific IgG antibodies is about 94% in healthy adults [18] . However, Kantola et al. recently showed cross-reactivity between the VP2 VLPs of HBoV1-4, which can largely affect the seropositive data of HBoV species. They showed that after depletion of cross-reactive antibodies, the approximate seroprevalences of HBoV1-4 in adults were 59%, 34%, 15%, and 2%, respectively [22] . However, the samples used in that study were only collected from healthy young people with a narrow range of age, including 115 subjects aged 21-32 years from Finland and 80 subjects aged 18-20 years from Pakistan. Given that the prevalence of a virus infection may vary by age as well as geographically, there remains to be a need to estimate the seroprevalence of HBoVs based on the detection of antibodies against HBoV1-4 from data of a more complete age range and from other global, geographic regions.