Unrecognized Transmission Risks of Occult Hepatitis B Virus Infection Among Blood Donors in Central Ethiopia

Occult hepatitis B virus infection (OBI) refers to the detection of HBV DNA in blood or liver tissue in individuals who test negative for hepatitis B surface antigen (HBsAg), excluding the early phase of acute HBV infection. This hidden form of infection represents a substantial but frequently underestimated risk to blood transfusion safety, particularly in settings with limited resources. In Ethiopia and other low-income countries, routine screening of blood donors often depends solely on HBsAg tests, which may overlook symptom-free carriers with low viral loads. This study was conducted to estimate the prevalence of OBI among HBsAg-negative blood donors and to assess its potential contribution to undetected HBV transmission in central Ethiopia.

Five hundred and eighty-two plasma samples from HBsAg-negative donors were analyzed. Initial screening for anti-Hepatitis B core antibodies (anti-HBc) was carried out using an enzyme-linked immunosorbent assay (ELISA). Samples that tested positive for anti-HBc were then analyzed for HBV DNA using the Abbott m2000 automated real-time polymerase chain reaction (RT-PCR) system. At the same time, information on sociodemographic characteristics and potential clinical risk factors for HBV exposure was obtained through structured questionnaires. Data were analyzed with SPSS Version 21, and statistical significance was considered at a p value of less than 0.05.

In this study, screening of 582 blood donors who were negative for HBsAg revealed that 135 (23.2%) donors, or nearly one-quarter, showed evidence of previous HBV exposure through anti-HBc reactivity. Subsequent molecular testing (PCR) identified a small proportion of these individuals carrying HBV DNA, confirming occult infection. Viral loads in all confirmed cases were low. Older donors, particularly those above 35 years of age, demonstrated a markedly higher rate of anti-HBc positivity. Overall, the occurrence of OBI was estimated at 1.7%, or approximately 17 cases for every 1000 blood donations, highlighting a critical gap in the current HBV screening protocol.

The findings demonstrate that a notable number of blood donors in central Ethiopia carry occult HBV infection, equivalent to 17 cases per 1000 donations. This indicates a concealed yet important risk of HBV transmission through blood transfusion. These results underscore the need to enhance donor screening protocols by incorporating both anti-HBc testing and nucleic acid testing (NAT) to improve transfusion safety and prevent the spread of undetected HBV.