CD4 and HIV infectious disease: In a scenario where antiretroviral treatment has been shown to dramatically reduce mortality rates attributable to HIV-infection and where improvements in antiretroviral treatment have further reduced mortality rates among HIV-infected individuals, the significant association of lower CD4 cell counts with higher rates of death due to AIDS and non-AIDS related causes supports the numerous arguments for earlier initiation of antiretroviral treatment [14], [15], [16], [17].