Molecular diagnosis of occult HCV and HBV infections

Occult HCV and HBV infections are recently identified entities whose existence became evident when nucleic acid amplification assays of enhanced sensitivity were employed for the detection of viral genomes and their replicative intermediates. These long-term silent infections are consequences of persistent low-level viral replication progressing in hepatocytes as well as in cells of the immune system. Detection of these new forms of HCV and HBV persistence requires a thorough testing approach in which analysis of serial serum and peripheral blood lymphoid cell samples and, when feasible, liver tissue samples is performed under strict contamination-controlled conditions using nucleic acid amplifications targeting different regions of viral genomes. This review focuses on the identification and general characteristics of occult HCV and HBV infections, and also acknowledges data from experimental occult infection in the woodchuck model of hepatitis B.