CD4 and viral infectious disease: Median values of CD4+ cells decreased significantly from BL to T2 in patients with RV starting with X4 tropic virus infection and experienced a tropism switch (590 cells/mm3, IQR 567–830 cells/mm3 at BL, 570 cells/mm3, IQR 570–667 cells/mm3 at T1 and 546 cells/mm3, IQR 497–560 cells/mm3 at T2, p = 0.04), even if the cell count was always higher than 500 cells/mm3.