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Impact of HCV Testing and Treatment on HCV Transmission Among Men Who Have Sex With Men and Who Inject Drugs in San Francisco: A Modelling Analysis
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Abstract
Background
Men who have sex with men who ever injected drugs (ever MSM-IDU) carry a high hepatitis C virus (HCV) burden. We estimated whether current HCV testing and treatment in San Francisco can achieve the 2030 World Health Organization (WHO) HCV elimination target on HCV incidence among ever MSM-IDU.
Recent research led by our group suggested different sociodemographic characteristics and injecting and sexual risk behaviors between MSM-IDU (ie, men reached through affiliation with MSM) and men reached through affiliation with PWID, whether they engage or not in male-to-male sex (PWID-MSM and PWID non-MSM, respectively) [7]. International evidence using phylogenetic analyses also suggests that the HCV epidemics among MSM and PWID are distinct [49], though similar research is needed in San Francisco.
Methods
A dynamic HCV/HIV transmission model among MSM was calibrated to San Francisco data, including HCV antibody (15.5%, 2011) and HIV prevalence (32.8%, 2017) among ever MSM-IDU. MSM had high HCV testing (79%-86% ever tested, 2011-2019) and diagnosed MSM had high HCV treatment (65% ever treated, 2018). Following coronavirus disease 2019 (COVID-19)-related lockdowns, HCV testing and treatment decreased by 59%.
Results
Among all MSM, 43% of incident HCV infections in 2022 were IDU-related. Among ever MSM-IDU in 2015, HCV incidence was 1.2/100 person-years (95% credibility interval [CrI], 0.8-1.6). Assuming COVID-19-related declines in HCV testing/treatment persist until 2030, HCV incidence among ever MSM-IDU will decrease by 84.9% (95% CrI, 72.3%-90.8%) over 2015-2030. This decline is largely attributed to HCV testing and treatment (75.8%; 95% CrI, 66.7%-89.5%). Slightly greater decreases in HCV incidence (94%-95%) are projected if COVID-19 disruptions recover by 2025 or 2022.
Conclusions
We estimate that HCV incidence will decline by >80% over 2015-2030 among ever MSM-IDU in San Francisco, achieving the WHO target.
Our findings indicating a pronounced decrease in HCV incidence among ever MSM-IDU and MSM non-IDU likely reflect San Francisco's multilayered efforts to increase HCV service access for high-risk populations through integration of services. San Francisco has long been a leader in the prevention and treatment of HIV for MSM, and several HIV-focused programs have added HCV testing and treatment into routine sexual health care.
In conclusion, despite a considerably higher HCV burden among ever MSM-IDU relative to MSM non-IDU in San Francisco and recent reductions in HCV testing and treatment due to the COVID-19 pandemic, our model suggests that the WHO HCV incidence target will be achieved in both populations. This finding can be attributed to the high intensity of HCV testing and treatment among MSM in this city, prior to COVID-19 disruptions, and illustrates what can be achieved by creating a robust HCV elimination program that prioritizes vulnerable populations.
Editorial
Redefining the Paradigm: The Role of Sexual Networks and Sexualized Drug Use in the Transmission of Hepatitis C Virus Among Men Who Have Sex With Men
Excerpts
Drug use among MSM is quite different than among PWID, however, in that it is sexualized rather than addictive behavior, that is, becoming "high" for the purposes of/in conjunction with sex, even with injection use (summarized in [4]).
we found that reinfection was not associated with sexualized drug use in either locale [3, 7], although the secondary analysis of the route of drug use in NYC found that sexualized methamphetamine use by injection was associated with reinfection [8], which we will return to
This is the context in which Artenie et al [9] present their mathematical modeling analysis estimating the success of the "End Hep C SF" public health initiative in reducing HCV prevalence and incidence among MSM in San Francisco, published in this issue of the Journal of Infectious Diseases. the data from which relative risk was calculated were from locales outside of, and during time periods before, significant sexual transmission among MSM, so they were more likely evaluating the consequences of addictive drug use by men who happened to have sex with men (ie, PWID), rather than sexualized drug use by the injection route in sexually active MSM.
To explain these associations, we propose a model derived from 2 lines of epidemiological evidence that we outlined above: first, that reinfection rates among MSM are much higher than primary infection rates; and second, that among MSM, although sexualized drug use was associated with primary infection in many studies, it was not overall associated with reinfection. The model that best fits these data is that participating in sexualized drug use, whether by injection or not, is an indication of being part of a sexual network in which the HCV prevalence is high; and conversely, that those who do not participate in sexualized drug use are part of sexual networks in which the HCV prevalence is low enough to result in few, if any, onward transmissions.
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