CD4 and severe acute respiratory syndrome: Our results are consistent with a previous study by He et al. that showed a sharp decline (below normal) in the cell counts of CD45+, CD3+ T cell subsets, CD4+ T cell subsets, and CD8+ T cell subsets during the first week of SARS-Cov infection; their values further declined during the second week before increasing during the third week and returning to normal by the fifth week.