Occult Hepatitis B Infection

Occult hepatitis B virus infection (OBI) is defined as the presence of HBV replicative templates in the liver with/without circulating HBV DNA in patients with undetectable hepatitis B surface antigen (HBsAg). The prevalence of OBI is estimated to be ranging from <1 to 18% in general population. Usually, serum HBV DNA level is low and intermittently detected, which does not induce liver damage. However, there are some potential risk for patients. Firstly, OBI has been reported to be associated with the development HCC in patients with chronic hepatitis C in some studies, but other studies did not find such an association. It is still a debating issue whether OBI may accelerate the disease progression toward cirrhosis and the development of HCC in patients with other chronic liver diseases. Secondly, there is potential risk of HBV transmission through blood transfusion from OBI donors. The risk could be minimized by screening the blood products using nucleic acid testing. Thirdly, HBV reactivation from OBI is being increasingly recognized when patients receive potent immune-suppressive therapies including B-cell depleting agents. Although prophylactic antiviral therapy minimizes the risk of HBV reactivation, the best strategy to prevent HBV reactivation in these situations remains to be defined. More research is needed to develop a useful guideline to optimize clinical management of OBI.