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||P.268 right column top paragraph: "Finally, the fidelity of RTs [reverse transcriptases] is higher than that of RdRps [RNA-dependent RNA polymerases](although it is still lower than that of DNA polymerases), resulting in lower mutation rates in retroviruses than in RNA viruses. For example, when not integrated into host genomes, rates of 0.1–0.2 mutations per genome, per generation have been estimated for viruses like the human immunodeficiency virus type-1 (HIV-1) and hepatitis B virus (HBV)[primary sources], a rate that is approximately fivefold lower than observed in some viruses that replicate using RdRps [primary source 10]. Hence, the rapid evolutionary dynamics that are exhibited by HIV-1 also reflect high rates of recombination [ref 15] and frequent positive selection [ref 16]."