HIV can’t grow or reproduce on its own. It requires cell of living organisms to infect & reproduce. HIV is specific to CD4+ cells in the human body i.e. cells with surface molecule called Cluster of Differentiation 4. Cells carrying this molecule are called CD4+ cells. Therefore HIV cant survive in the animal blood, because its only human blood that contains CD4+cells. HIV is a lentivirus. Like all viruses in this group it attacks the immune system. Lentiviruses are in turn part of a larger group of viruses called retroviruses. The term ”retrovirus” stems from the fact that these kinds of viruses are capable of copying RNA into DNA. The name lentivirus means slow virus. This is because they take such a longtime to produce any adverse effects in the body.