There is a negligible risk of transmitting HIV during sex when a person living with HIV is on antiretroviral therapy and maintains a viral load under a specific threshold. The systematic review, conducted by the Public Health Agency of Canada, relied on 11 studies and one previously published review to determine the absolute risk of HIV transmission when preventive measures are in place.
"Our findings show that there is a negligible risk of sexually transmitting HIV when an HIV-positive sex partner adheres to antiretroviral therapy and maintains a suppressed viral load of less than 200 copies/mL on consecutive measurements every four to six months. The risk of sexual HIV transmission is low when an HIV-positive sex partner is taking antiretroviral therapy without a suppressed viral load of less than 200 copies/mL, condoms are used or both," writes Rachel Rodin, Centre for Communicable Diseases and Infection Control, Public Health Agency of Canada, with co-authors.
"Based on our findings, relevant case law and other factors, the Department of Justice Canada concluded that the criminal law should not apply to people living with HIV who maintain a suppressed viral load of less than 200 copies/mL." Justice Canada also concluded that criminal law should generally not apply to those who use condoms, among others.
Previous studies found that antiretroviral therapy and condoms can reduce HIV transmission. This study includes evidence from newer studies that have influenced clinical practice and could affect Canadian criminal law.
"These findings will support individual patient and clinician decision-making, and will have implications for public health case management and contact tracing. The Department of Justice Canada used these findings to inform their 2017 report on the justice system's response to HIV non-disclosure, and they may inform the responses of other justice systems," write the authors.
In a related commentary, Richard Elliott, Canadian HIV/AIDS Legal Network, Toronto, Ontario, also welcomes Justice Canada's conclusions that the criminal law should generally not apply in various circumstances, including cases where condoms are used. However, he cautions that the qualitative descriptions of HIV transmission risk used by the study authors potentially overstate risk as understood in the criminal justice system.
"(The study authors') qualitative assessments of transmission risk apply risk categories originally developed 30 years ago to enable public education about safer sex and health risk reduction in general," Elliott writes. "These categories reflect the relative riskiness of different activities. But they should not be transposed into a system tasked with determining criminal liability based on risk associated with a single act."
Elliott suggests instead that "consensus statements of expert scientific opinion that specifically address the needs of the criminal justice system should guide that system." These support a more limited use of the criminal law than is currently the case in Canada.
Background: The Public Health Agency of Canada reviewed sexual transmission of HIV between serodiscordant partners to support examination of the criminal justice system response to HIV nondisclosure by the Department of Justice of Canada. We sought to determine HIV transmission risk when an HIV-positive partner takes antiretroviral therapy, has a suppressed viral load or uses condoms.
Methods: We conducted an overview and systematic review update by searching MEDLINE and other databases (Jan. 1, 2007, to Mar. 13, 2017; and Nov. 1, 2012, to Apr. 27, 2017, respectively). We considered reviews and studies about absolute risk of sexual transmission of HIV between serodiscordant partners to be eligible for inclusion. We used A Measurement Tool to Assess Systematic Reviews (AMSTAR) for review quality, Quality in Prognosis Studies (QUIPS) instrument for study risk of bias and then the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence across studies. We calculated HIV incidence per 100 person-years with 95% confidence intervals (CIs). We assigned risk categories according to potential for and evidence of HIV transmission.
Results: We identified 12 reviews. We selected 1 review to estimate risk of HIV transmission for condom use without antiretroviral therapy (1.14 transmissions/100 person-years, 95% CI 0.56–2.04; low risk). We identified 11 studies with 23 transmissions over 10 511 person-years with antiretroviral therapy (0.22 transmissions/ 100 person-years, 95% CI 0.14–0.33; low risk). We found no transmissions with antiretroviral therapy and a viral load of less than 200 copies/mL across consecutive measurements 4 to 6 months apart (0.00 transmissions/100 person-years, 95% CI 0.00–0.28; negligible risk regardless of condom use).
Interpretation: Based on high-quality evidence, there is a negligible risk of sexual transmission of HIV when an HIV-positive sex partner adheres to antiretroviral therapy and maintains a suppressed viral load of less than 200 copies/mL measured every 4 to 6 months. Sexual transmissions of HIV have occurred when viral load was more than 200 copies/mL with antiretroviral therapy or condoms alone were used, although the risk remains low. These findings will help to support patient and clinician decision-making, affect public health case management and contact tracing, and inform justice system responses to HIV non-disclosure.
Jennifer LeMessurier, Gregory Traversy, Olivia Varsaneux, Makenzie Weekes, Marc T Avey, Oscar Niragira, Robert Gervais, Gordon Guyatt and Rachel Rodin
[link url="https://www.eurekalert.org/pub_releases/2018-11/cmaj-nro111318.php"]Canadian Medical Association material[/link]
[link url="http://www.cmaj.ca/content/190/46/E1350"]Canadian Medical Association Journal abstract[/link]