Interrupting HIV Transmission Networks: How can we design and implement timely and effective interventions?

While remarkable progress has been achieved in HIV treatment and prevention over the past decade through widespread access to and use of antiretrovirals, HIV incidence has yet to substantially decline among key population in the United States (US). The federal Ending the HIV Epidemic (EHE) initiative launched in 2019 aims to reduce HIV infections by 90% by 2030 through focusing on four pillars: rapid diagnosis, early antiretroviral treatment (ART) initiation, expanded prevention (pre-exposure prophylaxis [PrEP]), and rapid response to outbreaks [1]. Mathematical modeling of the implementation of the first three pillars suggests that while substantial reductions in HIV incidence can be achieved, reaching EHE targets may be difficult in many jurisdictions [2]. There is no ‘one-size fits all’ combination of strategies because of the heterogeneity of the epidemic across population groups and geography. Planning interventions directed toward ongoing transmission thus requires a detailed understanding of the local epidemiology. The US HIV epidemic is comprised of sub-epidemics that overlap in time and space, formed by a confluence of biological as well as social factors. Ultimately, the intersection of sexual and/or injection drug use (IDU) behaviors in networks with HIV viremia leads to ongoing HIV transmission. Overall, nearly 36% of PWH in the US are not virally suppressed, and there are significant disparities along the HIV care continuum that persist by geographic region, between racial/ethnic groups, and sexual gender minority groups [3]. The entry of HIV into IDU networks, which have increased over the past decade due to the surge in the US opioid epidemic, has led to several explosive HIV outbreaks [4]. Consequently, several monitoring systems are employed to detect geographic areas with rapid HIV transmissions [5,6]. In many areas, new HIV infections may not arise from explosive cluster outbreaks [7] yet should remain important in public health monitoring and response activities. We outline here several elements that are key when designing effective and timely interventions based on HIV information reported into public health data systems including through the lens of current practices using HIV sequence data. While adequate public health funding and capacity building are paramount to successful interventions, we concentrate here on the importance of detecting early ‘incident’ HIV infection, understanding local HIV transmission networks and outbreak detection, and the need for meaningful community engagement.