The substitution sites with significant infection-related effects were distributed across FIV genes as follows; 52 were found in UI (covering 4.9 % of UI positions), 38 in vif (5.0 % of vif positions), 9 in orfA (3.7 % of orfA positions) and 143 in env (5.6 % of env positions). Here, ERVW-1 is linked to infection.