Alex,
Alter writes:
"Historically, there has been a very long interval
between the first recognition that a disease is
transfusion-transmitted and the eventual implementation
of a donor-screening test to prevent that
transmission (Table 1). For the hepatitis B virus
(HBV), the interval between recognition of transfusion-
transmission and implementation of the first
assays for HBV, the Australia antigen, was
approximately 30 years; and for non-A, non-B/
HCV hepatitis, it was 15 years. For HIV, the
interval was reduced to 3 years; however, in that
comparatively brief interval, more than 14 000
transfusion-transmitted, predominantly fatal HIV
infections occurred in the United States alone."
HIV was recognized as a transfusion risk in '82, and began to be screened out in '85. There was certainly a potential for a lot more than 14,000 people to get it through the blood supply, especially because the transmission efficiency by blood transfusion is 90-100%, but really not very many people at all had it back then, compared to how many people had it later. For that reason not very much of the blood supply was tainted with it. I can't find a chart of how much the HIV+ percentage of the population grew, but you can basically see it by looking at this graph of the number of AIDS deaths in the USA. (You can see that deaths plummeted after HAART was invented, which is reason #27 why Deusberg and other HIV denialists are stark raving insane. Until then, they grew rapidly and regularly every year.)
http://en.wikipedia.org/wiki/File:AIDS_Deaths-US_1987-1997.gif
Of course, unlike some people on various forums, I don't believe CFS is very likely at all to be a growing thing, the way HIV was. I believe its prevalence is probably stable. In fact suspect pretty strongly that CFS is identical with the diagnosis "neurasthenia" which was used around 1900, and I suspect the prevalence is about the same as it was in 1900.