CD4 and HIV infectious disease: Three scenarios can produce latent HIV infection in resting CD4+ T cells: (i) productive infection of activated CD4+ T cells that survive long enough for the cell to transition to a resting memory state, (ii) infection of CD4+ T cells that are transitioning from an activated to a resting memory state, and (iii) direct infection of resting CD4+ T cell (Chavez et al, 2015).