Disease progression in the absence of therapy can evolve in three distinct patterns; the normal progressors with a progressive loss of CD4+ T cells over six to eight years before developing AIDS, the rapid progressors whose loss of CD4+ T cells occurs within less than two years, and the long-term non-progressors in whom the CD4 count remains stable and the viral load is less than 50 copies/mL [140,141]. Here, CD4 is linked to AIDS.