AIDS virus (HIV) transmission by transfusions and blood products has been essentially halted in industrialized countries which haye introduced systematic anti-HIV screening of donations in 1985. New anti-HIV screening assays, based in part on the replacement of disrupted HIV virions by defined DNA recombinant HIV antigens, have improved specificity; sensitivity has been improved as to dectect seroconversion at an earlier stage. Confirmatory assays and (self-)exclusion of risk groups from blood donation do remain mandatory. HIVAg can be detected in some infections before antibody conversion, and HIVAg is more likely to be found in those anti-HIV positives who proceed to disease. However, there is no justification so far for routine parallel HIVAg and anti-HIV screening. There is continued uncertainty how many HIV carriers have not (yet) developed antibody, but their numbers may have been overestimated. Studies to determine how many HIV transmitters have escaped blood bank detection, and why, need to be undertaken in spite of formidable logistic difficulties.The risk of developing AIDS is now estimated at 25-50 % within 10 years after the infectious contact. It is not clear whether the risk should be estimated differently in different groups or persons. In cities in Central Africa, 5-20 % of men and women are confirmed anti-HIV positives. At least 75 % of this HIV carrier rate is due to heterosexual transmission. Heterosexual transmission has been slower in Western countries, but factors precluding slow evolution to high figures by the same route outside Africa have not been identified. Therefore, countries have no choice in advocating behaviour changes in the general population, and not only in the classical risk groups. Initial hesitations toward extended voluntary and confidential screening are dwindling. Well-conceived confidential screening may be the only way to avoid strong-armed government intervention. The latter is certain to be divisive, and is likely to be counterproductive on balance.An efficacious vaccine remains remote, but an antiviral which prolongs life by at least several months in AIDS patients, but not all of them, is now available. Zidovudine (AZT), however, is toxic and mere prolongation of life without cure will impose an additional burden on AIDS economics.A novel virus (HIV-2) has been identified and is already widespread in West-Africans. It causes AIDS, but the present ratio of AIDS cases in those infected seems lower than with HIV(-l); this feature may be transient. HIV-2 antibodies are either detected or missed by anti-HIV-1 screens; if found, they can be distinguished from anti-HIV-1 only by special confirmatory technique. New screening assays showing equal sensitivity for HIV-1 and HIV-2 in a single test should be devised. At present, HIV-2 is very rare in Western countries compared to HIV-1.
False-Positive HIV-1 Test Results in a Low-Risk Screening Setting of Voluntary Blood Donation