Relation Between HIV Viral Load and Infectiousness: a Model-Based Analysis, David Wilson et al., The Lancet (2010)

(The following summary is excerpted from the article's abstract):
A consensus statement released on behalf of the Swiss Federal Commission for HIV/AIDS suggests that people receiving effective antiretroviral therapy—ie, those with undetectable plasma HIV RNA (<40 copies per mL)—are sexually non-infectious. The authors analysed the implications of this statement at a population level. The authors used a simple mathematical model to estimate the cumulative risk of HIV transmission from effectively treated HIV-infected patients (HIV RNA <10 copies per mL) over a prolonged period. They investigated the risk of unprotected sexual transmission per act and cumulatively over many exposures, within couples initially discordant for HIV status. The analyses suggest that the risk of HIV transmission in heterosexual partnerships in the presence of effective treatment is low but non-zero and that the transmission risk in male homosexual partnerships is high over repeated exposures. If the claim of non-infectiousness in effectively treated patients was widely accepted, and condom use subsequently declined, then there is the potential for substantial increases in HIV incidence.