How is it that one person can have sexual intercourse with an HIV-positive partner and not become infected, while someone else can do the same thing, and bingo!, transmission happens. This has been one of the frustrating puzzles about the AIDS epidemic, sometimes expressed as “whew, what luck!” It turns out that luck may not have as much to do with it as viral load, i.e., how much HIV the infected partner has in his/her body.
Now comes a clinical study that demonstrates as true what we’ve suspected intuitively: HIV viral load (VL) is the most important predictor of HIV transmission between men and women. Lower VL equals less likelihood of transmission; higher VL, especially above 10K, increases the risk.
This particular study, funded by the National Institutes of Health but conducted in Uganda, also showed that HIV transmits with equal ease from female to male as from male to female, if both partners do not enjoy good genital health. Recent U.S. studies confirm this: having other sexually transmitted diseases (STDs) like syphilis ups the odds of infection. In correlation, not being circumcised also increases the risk, as uncut men are more likely to have penile health problems.
Two warnings about this study: First, it was about heterosexual vaginal intercourse, not anal sex. Second, just because a poz partner has a low VL does not mean that transmission cannot occur, just that the odds are lower. So, all the studies aside, safer sex practices are still in order. Like your mama said on rainy days, “If you’re going to go out [or in this case, go in], put your rubbers on!”
This article appears in May 12 • 2000.