Gaps and opportunities: measuring the key population cascade through surveys and services to guide the HIV response

Introduction: The UNAIDS 90-90-90 targets to diagnose 90% of people living with HIV, put 90% of them on treatment, and for 90% of them to have suppressed viral load have focused the international HIV response on the goal of eliminating HIV by 2030. They are also a constructive tool for measuring progress toward reaching this goal but their utility is dependent upon data availability. Though more than 25% of new infections are among key populations (KP)- sex workers, men who have sex with men, transgender people, people who inject drugs, and prisoners- and their sex partners, there is a dearth of treatment cascade data for KP. We assess the availability of cascade data and review the opportunities offered by biobehavioral and programme data to inform the HIV response. Discussion: The emphasis on the collection of treatment cascade data among the general population in higher prevalence countries has not led to a similar increase in the availability of cascade data for KP. The limited data available for KP highlight large gaps in service uptake across the cascade, particularly in the first 90, awareness of HIV status. Biobehavioral surveys (BBS), with linked population size estimation, provide population-based data on the treatment cascade and should be conducted every two to threeyears in locations with services for KP. With the inclusion of viral load testing, these surveys are able to monitor the entire treatment cascade among KP regardless of whether these populations access HIV services targeting the general population or KP. BBS also reach people accessing services and those who do not, thereby providing a unique opportunity to learn about barriers to service uptake including stigma and discrimination. At the same time high-quality programme data can play a complementary role in identifying missed opportunities that can be addressed in real-time. Conclusions: Data are more important than ever for guiding the HIV response toward reaching 90-90-90 targets and eliminating HIV, particularly in the face of decreased funding for HIV and specifically for KP. Timely high-quality BBS data can be triangulated with high-quality programme data to provide a comprehensive picture of the epidemic response for KP.