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Modifiable risk factors identified for HIV-1 transmission in Africa
Hughes JP. J Infect Dis. 2012;doi:10.1093/infdis/jir747.
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Researchers have identified plasma viral load and condom use as modifiable risk factors for HIV-1 transmission among black HIV-1 serodiscordant couples, according to new findings published in The Journal of Infectious Diseases.
“We were able to precisely quantify the effect of several important factors on the risk of HIV transmission,” James P. Hughes, PhD, of the University of Washington in Seattle, told Infectious Disease News.
“While the average risk of transmitting HIV in a single sex act is not high — about one in 900 — this risk varies considerably depending on the infected person’s viral load, the use of condoms and other factors.”
Researchers led by Hughes analyzed data from a prospective study of black HIV-1–serodiscordant couples in Africa. At enrollment, 3, 6 and 12 months, and study exit, plasma HIV-1 RNA was measured in the infected partner, and HIV-1 seropositive partners reported the number of sex acts and condom use.
Among 3,297 couples, the researchers identified 86 linked HIV-1 transmissions. Linked transmission is a transmission between the study partners.
The unadjusted per-act risk of transmission from men to women (0.0019; 95% CI, 0.0010-0.0037) was approximately twice as high as the risk of transmission from women to men (0.0010; 95% CI, 0.00060-0.0017).
However, further adjustment for viral load of the infected partner, herpes simplex virus type 2 serostatus and age of the uninfected partner indicated that the RR for male-to-female vs. female-to-male transmission was 1.03 (P=.93).
“This difference can be explained by differences in viral load of male vs. female infected partners, and differences in age and the presence of genital herpes in male vs. female susceptible partners,” Hughes said.
The researchers also found that each 10-fold increase in plasma viral load was associated with a 2.9-fold (95% CI, 2.2-3.8) increased risk of transmission, whereas reported condom use was associated with a 78% (RR=0.22; 95% CI, 0.11-0.42) decreased risk of transmission.
“These results provide additional evidence that strategies such as reducing viral load in HIV-infected individuals (using antiretroviral therapy, for instance), promoting male circumcision in HIV-uninfected men and promoting condom use can significantly reduce the risk of HIV transmission,” Hughes said.
In an accompanying editorial, Ronald H. Gray, MD, MSc, and Maria J. Wawer, MD, both of Johns Hopkins University, wrote, “It is reassuring that this large study by Hughes et al replicated findings from many prior studies; it also probably provides the most precise estimates of transmission per coital act during latent HIV disease.”
Disclosure: This research was supported by funding from the Bill & Melinda Gates Foundation (26469) and the NIH (AI029168 and AI083034).
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