ERVW-1 and viral infectious disease: This is in good agreement with previous estimates of significant temporal changes at 22 months based on genomic sequences of similar length (∼1100 nt) in gag-pol[13], which evolves much slower than env. Note, however, that selection during drug treatment may potentially act upon existing variants/subpopulations at a much faster rate [56], [57], but, as we show here, during chronic, asymptomatic, untreated viral infection evolution proceeds mostly by neutral drift over shorter time frames.