HIV stands for human immunodeficiency virus, and it is one "bug" that we as a species can't seem to kick. HIV infection weakens the immune system to the point that it can't fight off anything anymore, and something as simple as the common cold can turn fatal. The virus attacks T cells and CD4 cells, both of which we need to fight off infection. HIV eventually fights off so many CD4 cells that the body cannot battle any infection or illness, at which point the person develops full-blown AIDS. AIDS, or acquired immune deficiency, is when your immune system is not working as it should. HIV/AIDs can be acquired through blood transfusions or the sharing of needles or bodily fluids.al.