Replicates the viral genomic DNA. This polymerase possesses two enzymatic activities: DNA synthesis (polymerase) and an exonucleolytic activity that degrades single-stranded DNA in the 3'- to 5'-direction for proofreading purpose. a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) The N-terminus contains the 3'-5' exonuclease activity and the C-terminus contains the polymerase activity. This DNA polymerase requires a protein as a primer. Belongs to the DNA polymerase type-B family.