Occult hepatitis B infection - unveiling clinical burden and new diagnostic strategies

Occult B infection (OBI) represents a mild form of hepatitis B characterized by low-level HBV-DNA in the absence of positive serum HBsAg. OBI is associated with liver disease and HBV transmissibility, although to a lesser extent than overt (HBsAg+) chronic hepatitis B.

Residual HBV replication in the liver of OBI patients has been associated with i) increased risk for cirrhosis and/or liver cancer, ii) HBV transmission to recipients of organs or hemoderivates, iii) overt HBV reactivation under immunosuppression, and iv) extrahepatic manifestations.We searched PubMed with the keywords "occult hepatitis B," "occult B infection" or "OBI.'

The WHO has called for reducing 90% new HBV infections and 65% HBV-related mortality by 2030. The persistence of low-level virus replication in persons who cleared serum HBsAg is challenging. OBI misdiagnosis has emerged as a major obstacle for global HBV elimination. Efforts for unveiling OBI carriers are warranted, increasing clinical suspicion and expanding testing. New diagnostic tools, including more sensitive HBsAg and HBV-DNA tests and novel HBV-RNA and HBcrAg assays, may help unveil OBI carriers. Furthermore, point-of-care HBV-DNA assays will allow testing larger populations for OBI. New antivirals should target this form of hidden hepatitis B.