On May 2010, due to supports the widespread use of antiretroviral drugs to help control the AIDS pandemic, researchers said that HIV patients who took antiretroviral therapy (ART) were far less likely to infect their partners.

Reported in the Lancet, the researchers said that using the drug cocktail reduced the likelihood of transmission by 92%.
According to them, the findings mean ART might be a useful prevention tool as well as a treatment.

Dr. Connie Celum, professor of medicine and global health at the University of Washington, who involved in the study, whereas the study funded by the Bill and Melinda Gates Foundation and the U.S. National Institutes of Health, said, “these results are… the strongest evidence to date that ART might decrease HIV transmission risk.”

3,381 couples analyzed by researchers from seven African countries.
Of each couple, only one partner was positive for HIV, but at enrollment, the HIV-infected participants had CD4 counts of 250 cells per microliter or greater and did not meet national guidelines for ART initiation.

The reason that the team studied transmission in couples because they were easier to keep track of. All of the couple were given counseling on HIV prevention methods.

During 24 months of follow-up, 349 HIV-infected partners started ART. In the overall cohort, there were 103 cases of genetically-linked HIV transmission – but only transmission occurred after the infected partner started on ART.

The transmission rate per 100 person-years was 0.37 in those who had initiated ART and 2.24 in those who had not (p = 0.004).

The researchers write, “in participants not on ART, the highest HIV-1 transmission rate (8.79 per 100 person-year) was from those with CD4 cell counts lower than 200 cells per microliter.”
When the untreated HIV-1 infected partner had a CD4 cell count greater than 200 cells per microliter, 66 (70%) of 94 transmission occurred when plasma HIV-1 concentrations were above 50,000 copies/mL.

The authors wrote, “these observational data strongly support the hypothesis that ART substantially reduces HIV infectiousness and transmission risk.”

They concluded, ;”low CD4 cell counts and high plasma HIV-1 concentrations might guide use of ART to achieve an HIV-1 prevention benefit. Provision of ART to HIV-1 infected patients could be an effective strategy to achieve population-level reductions in HIV-1 transmission.”