Some 20 years ago, Dean Hamer reported an association between certain DNA markers and being gay . The report was met with considerable skepticism. Now a new study  has reached much the same conclusion as Hamer. This may be relevant to the apparently greater frequency of “HIV-positive” among gay men.
Overall data are clear, that “HIV-positive” does not behave like an infectious condition . More specifically, if “HIV-positive” is ever transmitted sexually then it is with essentially negligible probability, according to the Centers for Disease Control & Prevention:
Heterosexual vaginal transmission is estimated as less than 1 per 1000, but receptive anal intercourse is estimated at 1.4%. This is still less by a large factor than the transmissibility of known venereal diseases like syphilis and gonorrhea. Where does the estimate originate?
It cannot be based on observations in prisons since several such studies reported much lower rates there (p. 47 in ). Rather, the estimate likely comes from data on “HIV-positive” among gay men who frequently practice receptive intercourse. In other words, there is a correlation between being gay, receptive anal practices, and testing “HIV-positive”. In prisons, there is a significant amount of anal intercourse by men who are not gay, yet this apparently does not correlate with becoming “HIV-positive”. Evidently it is being gay, more than anal intercourse, that correlates with being “HIV-positive”.
If there is a genetic pre-disposition to being gay, as the Hamer and Sanders studies indicate, then perhaps there is also a genetic pre-disposition among gay men to testing “HIV-positive”.
That some genetic characteristics do predispose to testing “HIV-positive” is demonstrated by racial differences. Men of sub-Saharan ancestry test “HIV-positive” at rates about 7 or 8 times greater than with Caucasian men and about 10 times greater than with Asian men. There are also racial differences in the sensitivity of “HIV” tests to the p24 protein which is one of the “HIV” markers (section 3.4 in The Case against HIV).
I’m not suggesting, of course, that genes could be the sole reason why gay men are more frequently “HIV-positive” than others. Genetic pre-dispositions are probabilistic. Not all gay men test “HIV-positive”. In the earliest days of AIDS, only a small proportion of gay men became ill. Many gay men are both “HIV-positive” and healthy and never contract “AIDS”-type diseases.
Moreover, “HIV-positive” reflects any number of possible conditions, most of which are experienced equally by gay men and everyone else (section 3.2.2 in The Case against HIV).
Similarly, the Hamer and Sanders studies do not suggest that genetics determines sexual orientation, merely that it can bring a heightened tendency; it is explicitly a small effect, to the degree that genetic studies on infants or embryos could not have any useful predictive value . It is widely agreed that behavioral characteristics in general arise from some combination of hereditary and environmental factors. Moreover, it remains to compare the frequent correlation of certain genetic factors with being gay to the overall frequency of those particular factors among all men, which would indicate how strongly those factors may predispose toward a preferred sexual orientation.
So explanations for the greater incidence of “HIV-positives” among gay men are obviously and necessarily partial and multiple. I believe that some proportion of “HIV-positives” among gay men, correlated with also becoming ill, can be explained by the intestinal dysbiosis theory. Here I am suggesting that one possible and additional reason why some gay men are “HIV-positive” may be a genetic pre-disposition, particularly when “HIV-positive” does not correlate with a high probability of illness. Since the markers identified by Hamer and Sanders are not exclusive to gay men, a linkage between those markers and testing “HIV-positive” could also explain some of the incidence of “HIV-positive” among men who are not gay.
 Dean H. Hamer et al., “A linkage between DNA markers on the X chromosome and male sexual orientation,” Science 261 (1993) 321-7
 A. R. Sanders et al., “Genome-wide scan demonstrates significant linkage for male sexual orientation”, Psychological Medicine 45 (2015) 1379-88
 Henry H. Bauer, The Origin, Persistence and Failings of HIV/AIDS Theory, McFarland 2007