During the five-year period, significant differences in the HIV-1 infections were found by age (p < 0.001), occupation (p < 0.001), marital status (p = 0.007), educational level (p = 0.002), initial CD4 counts (p < 0.001), homosexual partner (p < 0.001), and sample source (p < 0.001). Here, CD4 is linked to HIV-1 infection.