[HIV transmission via blood transfusions: a study by the Swiss Red Cross blood bank service].

An inquiry amongst blood transfusion services served to establish at 19 the number of known transfusion associated HIV infections in Switzerland. In 12 cases the transfusion of an anti-HIV positive blood unit could be proven retrospectively, while in 7 cases an HIV-infected blood donor could not be found but the association of the infection with blood transfusion is highly probable by exclusion of other risk factors. All these infections occurred before introduction of anti-HIV screening in Switzerland in November 1985. After this date no new transfusion associated HIV infections have been reported. It is estimated that there are fewer than 170 transfusion associated HIV infections in Switzerland. The probability of infection with AIDS by blood transfusion is less than 1:500,000. Blood transfusion today appears to be as safe as before the emergence of the AIDS epidemic.