Glossary

AIDS (acquired immunodeficiency syndrome) - The last and most severe stage of the clinical spectrum of HIV-related disease.

Antibodies - Immunoglobulin molecules in the blood produced by the body's immune system and directed against specific agents, such as "alien" viruses or bacteria. In HIV infection, the antibodies produced against the virus for some reason fail to protect against it.

Asymptomatic - Without symptoms.

Autologous transfusion - Transfusion of a person's own blood that has been donated and stored prior to need, or salvaged during or after an operation and reused.

Bacteria - Microbes composed of single cells that reproduce by division. Bacteria are responsible for a large number of diseases. Bacteria can live independently, in contrast with viruses, which can only survive within the living cells that they infect.

Bisexual - A person who is sexually attracted to both males and females.

Condom - One type of prophylactic that can prevent sexually transmitted diseases and AIDS.

DNA (deoxyribonucleic acid) - A nucleic acid that carries genetic information in all organisms except certain viruses, the RNA viruses, which include HIV.

ELISA - Enzyme-linked immunosorbent assay. A laboratory test to determine the presence of antibodies to HIV in the blood. A positive ELISA result generally is confirmed by the Western blot test.

False-negative HIV antibody test - A negative test result that suggests a person is not HIV-infected when, in fact, he or she is infected.

False-positive HIV antibody test - A positive test result that suggests a person is HIV-infected when, in fact, he or she is not infected.

Heterosexual - A person sexually attracted to persons of the opposite sex. The word "straight" has become synonymous with heterosexual.

High-risk behaviour - Activities that put an individual at greater risk of developing a particular disease. High-risk activities associated with AIDS include unprotected sexual intercourse and sharing of needles and syringes.

HIV (human immunodeficiency virus) - The retrovirus that causes AIDS in humans.

HIV-1 - The retrovirus that is the principal worldwide cause of AIDS.

HIV-2 - A retrovirus closely related to HIV-1 that also causes AIDS in humans, found principally in West Africa.

HIV-antibody-negative - Containing no antibodies to HIV.

HIV-antibody-positive - Containing antibodies to HIV.

Homosexual - A person sexually attracted to persons of the same sex. Homosexuals include males (gays) and females (lesbians).

IDU - Injecting drug user

Immune system - All of the mechanisms that act to defend the body against external agents, particularly microbes (viruses, bacteria, fungi and parasites).

Incubation period - The period of time between entry of the infecting pathogen into the body and the first symptoms of the disease.

Kaposi’s sarcoma - A cancer or tumour of the walls of the blood vessels or the lymphatic vessels.

Lymphadenopathy - Swelling of the lymph nodes. Persistent and generalized lym-phadenopathy is one of the early clinical signs of HIV infection.

Maternal antibodies - In an infant, these are antibodies that have been passively acquired from the mother in utero. Because maternal antibodies to HIV continue to circulate in the infant's blood up to the age of 15-18 months, it is difficult to determine whether the infant is infected.

MSM - Men who have sex with men.

Opportunistic infection - An infection with a micro-organism that does not ordinarily cause disease, but that becomes pathogenic in a person whose immune system is impaired, as by HIV infection.

Pathogen - An agent such as a virus or bacteria that causes disease.

Plasma - The fluid portion of the blood.

Retrovirus - An RNA-containing virus that can transcribe its genetic material into the DNA of its host's cells by the action of an enzyme called reverse transcriptase. This is the reverse of the usual, or DNA-to-RNA, transcription.

RNA (ribonucleic acid) - A nucleic acid associated with the control of chemical activities inside a cell. Some viruses, including HIV, carry RNA instead of the more usual DNA.

Semen - Fluid produced by the seminal vesicles and the prostate that contains the spermatozoa. Semen can contain cells infected with the AIDS virus and is consequently able to transmit the infection to sexual partners.

Seroconversion - The development of antibodies in response to an antigen. With HIV, seroconversion usually occurs 4-12 weeks after infection is acquired, but in a very few cases, it has been delayed for six months or more.

Serological testing - Testing of a sample of blood serum.

Seronegative - Showing negative results in a serological test.

Seropositive - Showing positive results in a serological test. A person who is seropositive for HIV antibody is considered HIV-infected.

Seroprevalence - The proportion of a given population with a particular marker in the blood, such as antibody to HIV, at a specific time.

Serosurvey - Systematic testing of sera from a group of persons to determine the frequency of a particular marker, such as antibody to HIV, in that population.

STD - Sexually transmitted disease(s). These are diseases that can be transmitted by means of sexual relations. AIDS is essentially a sexually transmitted disease. STDs are increasingly being referred to as sexually transmitted infections.

Symptomatic - With symptoms.

Viraemia - The presence of virus in the blood, which implies active viral replication.

Virus - Infectious agent (microbe) responsible for numerous diseases in all living beings. They are extremely small particles, and in contrast with bacteria, can only survive and multiply within a living cell at the expense of that cell.

White blood cells - Blood cells responsible for the defence of the body against foreign disease agents and microbes. HIV targets two groups of white blood cells called CD4+ lymphocytes and monocytes/macrophages.