To determine the seroprevalence of HBoV1-4 in adults, we used the HBoV VLPs ELISA method to detect IgG antibodies against HBoV1-4 in 142 serum samples collected from healthy individuals 15-70 years old. Without competition, more than 90% samples were positive for HBoV1, HBoV2, and HBoV3; 73 (51.4%) samples were positive for HBoV4 (Table 1) . However, these IgG seroprevalences decreased with competition by VLPs of heterologous HBoV species (Figure 4 ). The cELISA resulted in seroprevalences of 66.9%, 49.3%, 38.7%, and 1.4%, for HBoV1, 2, 3, and 4 IgG, respectively. The seropositive rate of HBoV1 was higher than that of HBoV2, HBoV3, and HBoV4 (x 2 = 23,P,0.01) (Table 1 and Figure 5 ).