Can a low (OR NO) viral load make an HIVer less (or non-) infectious? African and U.S. researchers who conducted a 30-month-long study in rural Ugandan villages found that blood levels of HIV may help predict how likely an HIVer is to pass the virus on to a sex partner. Starting in 1994, the scientists tracked 415 serodiscordant heterosexual couples. All participants received aggressive treatment for sexually transmitted diseases such as syphilis (believed to facilitate HIV transmission) and a free supply of condoms, but—and it’s a but that has raised ethical concerns—no notification of their partner’s HIV status (although HIVers were urged by their doctors to disclose).
It was no surprise that the rubbers didn’t always meet the road: Ninety participants became infected. And the higher the positive partner’s viral load, the greater the risk. For every tenfold rise in viral load, transmission more than doubled. In 80 percent of the infections, the HIVer had counts greater than 10,000. Significantly, those with loads below 1,500 did not infect their partners. But before you undetectables out there trash your condoms, consider this: Other studies have found HIV in semen and vaginal fluids even when none showed up in the blood. And viral loads do bounce about—undetectable one day, bold as brass another. The lesson: Lower risk isn’t no risk.