In order to standardize the deÞ nitions the following terms were suggested: 1) infection (not necessarily associated with reactivation of hepatitis) in the case of the detection of HBV DNA by sensitive HBV assays and/or of HBsAg in patients in whom these markers were originally negative, 2) reactivation of hepatitis B (hepatitis), in the presence of a significant viremia and ALT levels above the upper normal value. The gene discussed is GPT; the disease is hepatitis A virus infection.