Expert Consensus: Viral Load and the Risk of HIV Transmission

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A more recent publication based on new studies has just been issued by the Ministère de la Santé et des Services sociaux. This update is titled «L'effet du traitement des personnes vivant avec le VIH sur le risque de transmission sexuelle de l'infection» (The impact of treating people living with HIV on the risk of sexual transmission of the infection) can be found here: http://publications.msss.gouv.qc.ca/msss/document-002173/ (french only).

The CITSS working group was mandated to assess the effect of undetectable viral load on HIV transmission risk in order to support updating the Estimation du risque associé aux activités sexuelles , a resource designed to help guide risk-reduction counselling and to support the assessment of STBBI reports according to section 95 of Québec's Public Health Act.

The CITSS has established that an undetectable viral load (fewer than 40 copies/mL, or below the minimal quantification threshold in force for testing kits in Québec), typically achieved after 16 to 24 weeks of treatment and maintained for at least 6 months and on 2 consecutive measures due to effective ART, reduces the HIV transmission risk for vaginal intercourse between heterosexual couples. The risk for condomless vaginal intercourse is therefore reduced from high to negligible or very low (II), as defined in section 2.2. With respect to the methodologies of the reviewed studies and their results, this finding applies only as long as the following conditions are consistently met:

Undetectable viral load maintained for at least 6 months and on 2 consecutive measures, due to effective ART
At least 95% treatment adherence
Partners in a stable and exclusive couple
Confirmed absence of STBBIs in both partners
Intensive medical follow-up for 3 to 4 months, including measurement of the viral load and STBBI screening for the PLHIV, and STBBI screening, including HIV screening, for the seronegative partner
Regular and appropriate counselling for both partners covering the above-mentioned conditions as well as risk reduction, including correct condom use.

If any of these conditions is not met, the risk may still be reduced. However, the available evidence does not allow estimating that risk. For PLHIV, the counselling should also address other issues, including awareness of legal aspects, conception, and immunization.

With respect to the risk associated with condomless oral sex between stable and exclusive couples, either heterosexual or homosexual, mathematical and theoretical estimates suggest that the risk would be reduced to negligible or very low when the viral load is undetectable for at least 6 months and on 2 consecutive measures due to effective ART. This finding applies only as long as the following conditions are consistently met (III):

Undetectable viral load maintained for at least 6 months and on 2 consecutive measures due to effective ART
At least 95% treatment adherence
Partners in a stable and exclusive couple
Confirmed absence of STBBIs in both partners
Intensive medical follow-up for 3 to 4 months, including measurement of the viral load and STBBI screening for the PLHIV and STBBI screening, including HIV screening, for the seronegative partner
Regular and appropriate counselling for both partners covering the above-mentioned conditions as well as risk reduction, including correct condom use.

According to mathematical and theoretical estimates, the risk associated with condomless insertive anal intercourse in stable and exclusive couples, either heterosexual or homosexual, when the viral load is undetectable for at least 6 months and on 2 consecutive measures due to effective ART may be the same as that for receptive vaginal intercourse, at negligible or very low. This finding applies only as long as the following conditions are consistently met (III):

Undetectable viral load maintained for at least 6 months and on 2 consecutive measures due to effective ART
At least 95% treatment adherence
Partners in a stable and exclusive couple
Confirmed absence of STBBIs in both partners
Intensive medical follow-up for 3 to 4 months, including measurement of the viral load and STBBI screening for the PLHIV and STBBI screening, including HIV screening, for the seronegative partner
Regular and appropriate counselling for both partners covering the above-mentioned conditions as well as risk reduction, including correct condom use.

Condomless receptive anal intercourse when the viral load has been undetectable for at least 6 months and on 2 consecutive measures due to effective ART carries a higher risk, but still within the negligible or very low category according to the established criteria (section 2.2). However, one case of transmission by presumed anal intercourse between a MSM couple has been reported in the literature, although the evidence of the transmission has been called into question. It cannot be excluded that the risk could be greater than negligible or very low. In the absence of compelling evidence, this conclusion is based on expert opinion alone (III). Therefore, this finding applies only as long as the following conditions are consistently met (III):

Undetectable viral load maintained for at least 6 months and on 2 consecutive measures due to effective ART
At least 95% treatment adherence
Partners in a stable and exclusive couple
Confirmed absence of STBBIs in both partners
Intensive medical follow-up for 3 to 4 months, including measurement of the viral load and STBBI screening for the PLHIV and STBBI screening, including HIV screening, for the seronegative partner
Regular and appropriate counselling for both partners covering the above-mentioned conditions as well as risk reduction, including correct condom use.

Finally, the consensus has established that even when the viral load is undetectable and all the above-mentioned conditions are met, there is no guarantee of zero risk. Some transmission risk may remain, albeit much lower.