Aids

the acronym for Acquired Immune Deficiency Syndrome, which was first recognized in Los Angeles in the USA in 1981. The causal agent was identified in 1983 as being the human immunodeficiency virus, known as HIV , a ribonucleic acid ( RNA ) RETROVIRUS . The virus has been found in blood, other body fluids, semen and cervical secretions and is mainly transmitted by sexual activity. The HIV virus affects the T-LYMPHOCYTES of the immune system (see IMMUNITY ) and leaves the patient increasingly unable to resist certain infections and tumours that are particularly associated with Aids. Although they may take a long time to develop, these infections eventually prove to be fatal, and at the present time there is no known cure for Aids.