HTLV-III was one of the early names for the AIDS virus, before it was renamed HIV. The viruses HTLV-I and -II were known before the AIDS epidemic, and when HIV was first discovered, it was thought to be related to those two viruses and so was named as the third type of HTLV. We now know it is not very closely related to the first two HTLVs. More recently, an entirely different virus was discovered and named HTLV-3 ( Arabic numeral, not Roman). It is very rare; it's among a group of viruses that are common in primates in Africa (monkeys, chimps, etc) and only a few cases have been found in humans. It is not yet known to be associated with any disease in humans, and whether it can be transmitted between humans -- by sex or anything else -- is not known. Here is a link to the most pertinent scientific report I was able to find: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7111966/ It could not have been diagnosed in your partner back in the 1980s, before it was even discovered and named.

So before we go further, please clarify the situation as best you can. Where is your partner from and where was he living as an infant when he received the blood transfusion? (Tropical Africa, for example?) It seems unlikely he actually has HIV; nobody uses "HTLV-III" to mean HIV anymore, and of course if he had HIV, he would have been treated for it starting in the 1990s or at least by the mid-2000s. Is there any chance he actually has HTLV-I or HTLV-II, not -III? But be aware that even if it turns out to be one of these viruses, very little is known about the potential for sexual transmission, or for infecting a baby. None of these viruses are considered STDs and I'm not going to be able too say very much about prevention. But I'll do my best if you can fill in the gaps.

Thanks again--   HHH, MD

I look forward to your replies.

If he can't find the report, perhaps the Red Cross facility where he donated probably can locate his record and provide more information -- although back in 2005, it is possible the records are hard copy, i.e. not digital and not in a computer database. But it's probably worth a try.  

I don't know much about HTLV-1 and -2 testing [now using the proper current terminology, i.e. Arabic numerals], but it's not rare; probably testing is available at the major national labs (like Quest or Labcorp). However, it is somewhat complex, starting with an initial screening test (antibody?) with follow-up confirmatory testing in selected circumstances. Your partner should not seek testing on his own, i.e. directly from a laboratory, but should see an infectious diseases specialist. Alternatively, an oncologist (cancer specialist) may help; most probably have experience in the course of managing patients with certain cancers. Your partner's personal physician probably can make an appropriate referral, perhaps after first ordering an initial test.

Of the two main types, HTLV-1 is by far the more common. It is transmitted to infants by breast milk, congenitally (mother to infant in utero), and sexually. However, there are no good data on actual frequency/risk in individual cases; it is likely that not everyone with a positive blood test has an active, transmissible infection. In countries where testing has been most frequent (e.g. Peru), HTLV-1 remains uncommon even in very sexually active populations. For example, one study found 4% of female sex workers tested positive after two years with up to hundreds of sex partners, and the frequency was lower in regular condom users. That suggests that the per-exposure transmission risk is low and that condoms are protective. But the exact risk level in a particular couple is very difficult to know.

Forum threads remain open for two follow-up comments or questions, so you have one to go; or after 4 weeks, whichever comes first. It seems it should not be difficult for him to know the scoop in that time. However, as I implied above, if confirmed to have an active HTLV-1 or 2 infection, there's not much more we'll be able to say. In that event, the aforementioned specialist is likely to have just as up to date information as we do, probably more. But I'll do my best if it comes to that!

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9008201/ 

Thank you for providing your insight and understanding of the disease and for sharing with me the most recent literature published on the matter. Hopefully my partner can get a new blood test within the next few weeks before this thread closes and I can share with you a confirmation of the exact HTLV type he has. If not, I will just open a new question if I have any further questions before we set up consultation with an infectious disease specialist.

Kind regards and thank you again for all the valuable information you provided.

Thanks for the thanks for the little I've been able to do. And for opening a stimulating topic!