One of these cases of triple infection was reported in a 35-year-old homosexual man who did not have clinical symptoms and who did not have a reduced CD4+ T-cell count when he was infected with two distinct subtype B strains, whereas infection of a third divergent CRF01_AE strain resulted in a high viral load with a markedly reduced CD4+ T-cell count and acute viral illness (van der Kuyl et al., 2005). This evidence concerns the gene CD4 and infection.