Not all the sub-Saharan African countries have high rates of HIV—the West African countries seem to have pretty low rates (assuming the reported figures are reasonably accurate). It’s mostly the extreme southern countries with very high rates (over 10%)—South Africa, Swaziland, Lesotho, Namibia, Zimbabwe, Mozambique, Botswana, Zambia.
And as reported:
although Africa which is often cited as showing HIV is mainly due to heterosexual relations, HIV/AIDS stats in Africa have a troubled history, (https://abrahamson.medill.northwestern.edu/WWW/IALJS/Malan_AidsInAfrica_RollingStone_22Nov2001.pdf), while a 2019 scholarly study reported that, "The results of the present study reveal the following: HIV prevalence is significantly higher in the populations of men who have sex with men than in men in the general population and, more specifically, in men in sub-Saharan Africa. In the 2015 UNAIDS (Joint United Nations Program on HIV/AIDS) report, studies in sub-Saharan Africa found prevalence rates of HIV infection ranging from 6 to 37% among MSM
As the observed prevalence rate of HIV in the general population was between 0.1 and 19%, the prevalence rate among men who have sex with men (MSM) was often 13 to 17 times higher." "In 2015, according to the progress reports on the global AIDS (Acquired Immune Deficiency Syndrome) response, the highest prevalence rates of HIV infection among MSM were as follows: 19% in central and western Africa; 15% in southern and eastern Africa; 12% in Latin America; 11% in the Asia-Pacific region; and 8% in central and western Europe and North America." (https://bmcpublichealth.biomedcentral.com/track/pdf/10.1186/s12889-019-8000-x.pdf)