Occult hepatitis B virus (HBV) infection: a global challenge for medicine.

Hepatitis B virus (HBV) is a serious risk as a disease that can be spread through blood transfusion. Occult hepatitis B infection (OBI) is defined in a patient with the presence of HBV-DNA but a lack of HBsAg in the serum and hepatocytes. OBI can be considered as a high potential risk factor for inducing post transfusion hepatitis (PTH), hepatocellular carcinoma (HCC), cirrhosis, and reactivation of the HBV. Recently, several investigations from various regions of the world have reported PTH as well as HCC and cirrhosis among blood recipients with diseases such as thalassemia and other disorders requiring regular hemodialysis. This form of hepatitis also causes complications for individuals that are co-infected with other viruses such as HCV and HIV. Because of its extreme disease potential, OBI can be considered a high risk for PTH, HCC, and cirrhosis. Therefore, an understanding of the prevalence of OBI among blood donors is a critical strategy in most transfusion services. This review addresses the recent information regarding the prevalence of OBI worldwide, with an additional focus on Iranian blood donors.