Speaker
Description
In July 2023, the WHO issued guidance indicating that individuals with HIV viral loads between 200-1000 copies/mL have a “negligible” risk of onward transmission to sexual partners, marking a shift from “undetectable = untransmittable” messaging. However, this guidance is based on limited empirical data, particularly from settings in Africa since widespread roll out of antiretroviral (ARV) drugs. A more precise understanding of transmission risk and associated uncertainties is needed to inform clinicians, modelers, and people living with HIV.
We used data from the Rakai Community Cohort Study in Uganda, tracking viral loads of 1,420 couples in stable heterosexual partnerships with discordant HIV status and a cumulative 2,258 person-years of follow-up between 1994 and 2020 during which 139 transmissions occurred to quantify the probability of transmission as a function of HIV-positive partner’s viral load. We fit the data to models with alternative hypotheses for i) the functional form of risk vs viral load (including mechanistic and non-mechanistic models), ii) the role of extra-partner transmission, and iii) viral load trajectories between samples.
The best estimate for transmission risk from an average individual with viral load between 200 and 1000 copies/mL was 0.007 [0.004, 0.014] conversions / year of sexual contact. Compared to the average log10 viral load in the cohort (3.7), the relative risk of transmission was 0.125 [0.067, 0.237]. Considering all models that fit the data comparably well, central estimates of the relative risk varied between between 0.11 and 0.30. We observed 0 conversions when the positive subject consistently had a viral < 200 copies/mL (with a total of 65.3 couple-years of observation), consistent with U=U messaging.
| Expedited Notification | No thanks, I do not require Expedited Notification |
|---|
