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 17th century. But the HIV strain responsible for the current epidemic is estimated to have emerged in the 1930s.
The Human Immunodeficiency Virus