From the performance of the molecular “nucleic acid test” for the detection of the hepatitis B virus (HBV NAT) in the screening of blood donors, a variable prevalence was found for carriers of viral DNA for HBV in asymptomatic donors negative for hepatitis B surface antigen (HBsAg), which characterized a new clinical form of infection, determined as an occult infection by the hepatitis B virus—HBV (OBI) [5,6]. The gene discussed is BRD2; the disease is infection.