[Infections with human immunodeficiency viruses. Part I: pathogens, epidemiology, and clinical presentation].

Human immunodeficiency viruses 1 (HIV-1) and 2 (HIV-2) are single-stranded, enveloped ribonucleic acid viruses of the retrovirus family (retroviridae). They are transmitted by unprotected sexual intercourse, the inoculation of HIV-contaminated blood into the bloodstream and from mother to child via the prenatal, perinatal and postnatal route (in breast-feeding women). In contrast to infections with HIV-2, HIV-1 infections are frequently distributed worldwide and belong to the most common severe infections in humans. 90% of all HIV-1 infected people, however, live in less developed countries, e.g., numerous areas in South and Eastern Africa. Without an appropriate antiretroviral treatment, HIV-1 infections lead after a perennial, individual-dependent period to a state of generalized low immunity (acquired immunodeficiency syndrome, AIDS), resulting in the establishment of several illnesses due to a wide range of opportunistic pathogens. In several less developed regions, these so-called AIDS-defining diseases still represent one of the most frequent causes of death.