What is HIV ?

The human immunodeficiency virus (HIV) is an organism known as a retrovirus. Like any virus, HIV must use the cells of another organism – its host – to survive and reproduce. HIV is adapted to using the cells of the human immune system.

HIV has its origin in the transmission of simian immunodeficiency viruses (SIVs) from non-human primates, mainly chimpanzees, to humans. Such zoonotic transmission is not unique – the virus that causes influenza, for example, was another animal virus that came into contact with humans and evolved successfully to become a human pathogen. Exactly when SIVs made the jump to humans from chimpanzees is still unclear, with some researchers putting it as early as the 17^th century. But the HIV strain responsible for the current epidemic is estimated to have emerged in the 1930s. 

The Human Immunodeficiency Virus