Earlier diagnosis would also give people the opportunity to make informed decisions about their sexual behaviour. Research suggests that most people diagnosed with HIV reduce their risk behaviour, in the short term at least. A meta-analysis of American studies, conducted with both heterosexuals and men who have sex with men, found that high-risk sexual behaviour was 53 to 68% less frequently reported in the months following diagnosis.

However, it is unclear whether this kind of behaviour change is sustained. Only a few studies have followed the same individuals for more than a year after being diagnosed and the results are contradictory. A study of Kenyan sex workers found that reductions in risky behaviour were maintained for several years after diagnosis. A study with Dutch gay men observed a fall in unprotected sex immediately after diagnosis, but four years later risk behaviour had returned to pre-diagnosis levels.

Of note, these kind of studies only rarely collect enough information to tell us about risk-reduction strategies which rely on knowledge of HIV status – for  example, only having unprotected sex with partners who also have HIV (‘seroadaption’ or ‘serosorting’) or, in the case of MSM, choosing sexual position according to each partner’s HIV status (‘strategic positioning’).