Occult infections (OBIs) due to hepatitis B virus (HBV) are identified by the presence of HBV DNA without surface antigen (HBsAg). The population prevalence of HBsAg is high in Benin, but there are no data concerning the presence of OBIs.
The aim of this study was to evaluate the presence of OBIs using samples taken from 220 pregnant Beninese women for the purposes of a previous study of the prevalence of HBV markers. Twenty-four women were HBsAg positive (group I); of the 196 HBsAg negative women, 164 had other HBV markers (group II) and 32 had no HBV marker at all (group III).
Forty-seven (24.0%) of the HBsAg-negative samples were positive for HBV DNA of which 46 (97.9%) in group II (seropositive OBIs) and 1 (2.1%) in group III (seronegative OBIs). About half of the women in groups II had viremia levels of < 20 IU/mL; the mean viremia levels in the remaining samples were 188.7 IU/mL in group II, although some of the women with OBIs had levels of as high as 1187 IU/mL.
The high prevalence of OBIs increases the number of potentially infected subjects in this area in comparison with the findings of tests based on the determination of HBsAg alone, which significant clinical and management implications for both vertical and horizontal transmission.