Up to a fifth of HIV infections among black African men initially classified as ‘heterosexual exposure’ in the UK are likely to have been acquired as a result of sex with other men, a new study suggests.
The researchers used a technique called phylogenetic analysis in order to compare the genetic structure of the virus in 22,500 people diagnosed with HIV. This technique can identify transmission clusters – in other words, groups of people who may have acquired HIV from each other. It is the technique that is sometimes used in evidence during prosecutions of HIV transmission.
The analysis was only of people who had subtype B. This is the strain of HIV that is most prevalent among men who have sex with men in the UK. (In African countries and among people who have moved from Africa to the UK, subtype C is generally more common.)
The researchers wanted to find out why an increasing number of individuals who describe themselves as heterosexual were being diagnosed with subtype B. One possibility is that this is because of more sexual mixing between men who have sex with men and heterosexual people, resulting in subtype B increasingly being passed on between men and women.
Another explanation is that some men are not disclosing that they have sex with other men when they test for HIV. The researchers found some evidence for this. Around a third of individuals (who had been described as heterosexual) were in transmission clusters in which all the other members were men who have sex with men.
This was most often the case for men of black African ethnicity.
Depending on the assumptions used, the researchers estimate that between 1 and 21% of black African men reported as heterosexual actually acquired HIV during sex with other men.
The researchers note that stigma and discrimination can make disclosure of same-sex behaviour more difficult for men in black African communities.
The results point to the need for HIV prevention interventions for black African communities to be inclusive and sensitive to the needs of men who have sex with men. Individuals may not readily disclose their same-sex behaviour or identify as gay, but need to have access to appropriate information and support. There is a further need for highly targeted work which is able to engage African men who have sex with men.