In accordance with this hypothesis, our data showed that though CD4+ T cells counts in HIV/HCV dual infection group were significantly higher and viral loads were significantly lower than that in HIV-1 monoinfection group at the baseline, a similar fraction of individuals in both groups was observed at AIDS stage with CD4+ T cells <200 cells/ul; it was only appeared at the last three visits that a significant less fraction of HIV/HCV dual infected subjects progressed into AIDS. Here, CD4 is linked to AIDS.