HIV: introduction and epidemiology

This chapter provides background information to the events that led to the discovery of HIV. Previously fit young men who have sex with men presented with certain infections and cancers, coupled with severe immune deficiency, which was later given the name acquired immune deficiency syndrome (AIDS). This chapter gives information about the origin of HIV and its link to simian immunodeficiency viruses (SIVs). This chapter provides information on the geographical, and the epidemiological differences between HIV-1 and HIV-2. The chapter also explains the biological implications of HIV types and subtypes. Risk factors and transmission routes are also discussed, in addition to UK and worldwide HIV prevalence data.