The most recent global HIV data have brought great optimism that controlling the HIV
epidemic could become a reality. These encouraging data show overall declines in both
AIDS‐related deaths and new HIV infections worldwide 1. Recent data also demonstrate
impressive gains toward the global 90‐90‐90 targets. As of 2016, an estimated 70%
of all people living with HIV (PLHIV) globally knew their HIV status. Among those
who had been diagnosed, 77% were accessing antiretroviral therapy, and 82% of people
on treatment had achieved viral suppression 1.
Despite this progress, the optimism is tempered by concern that reducing HIV incidence
rates must be further accelerated to guarantee epidemic control 2. Moreover, the recent
gains have not been uniform. While global data indicate important achievements in
addressing the epidemic among key populations – defined by the World Health Organization
(WHO) as men who have sex with men (MSM), sex workers, transgender people, people
who inject drugs (PWID), and prisoners 3 – these gains still lag far behind those
made in the general population.
UNAIDS estimates that 44% of all new HIV infections among adults worldwide occur among
key populations and their partners 1. In generalized epidemic contexts of sub‐Saharan
Africa, key populations and their sexual partners account for 25% of new HIV infections,
while in concentrated epidemic settings, they account for as much as 80% of infections
1. Globally, sex workers, MSM and PWID are 10, 24 and 24 times more likely, respectively,
to acquire HIV compared with the general population ages 15 years and older 4. Transgender
women are 49 times more likely to be living with HIV and prisoners are five times
more likely to be living with HIV compared to other adults 4, 5.
Growth in supporting HIV programmes for key populations
Evidence of the disproportionate epidemiological burden that members of key populations
shoulder has been met with important policy developments and funding commitments.
In 2014, the Global Fund to Fight AIDS, Tuberculosis and Malaria launched the Key
Populations Action Plan, reflecting its commitment to help meet their HIV prevention,
care and treatment needs and rights 6. That same year, WHO released consolidated guidelines
on HIV prevention, diagnosis, treatment and care for key populations 3. These guidelines
were updated in 2016 to reflect the urgent call to treat all individuals regardless
of CD4 count and to provide pre‐exposure prophylaxis (PrEP) to those “at substantial
risk” 7. Additional global implementation guidance and programmatic tools soon followed
to support key population programme design and scale up 8, 9, 10, 11, 12.
The President's Emergency Plan for AIDS Relief (PEPFAR) has also launched specific
initiatives to expand key populations’ access to and retention in HIV services. Through
programmes such as the Key Populations Challenge Fund, the Key Populations Implementation
Science Initiative and the Local Capacity Initiative, PEPFAR supported work to understand
and better serve key populations, as well as to strengthen capacity of key population‐led
organizations to address the epidemic in their communities 13. Moreover, PEPFAR recognizes
that “ensuring key populations have access to and increase their use of comprehensive
packages of health and social services” is essential for achieving epidemic control
Finally, the UNAIDS HIV Prevention 2020 Roadmap deems combination prevention programmes
for key populations necessary to accelerate declines in new HIV infections at country
level. The Roadmap calls for combination prevention programmes that are evidence‐informed,
community‐owned, and human rights‐based; implemented at scale; and tailored to the
specific needs of key populations 15.
Key populations, data challenges and the HIV cascade
These commitments are critical to advancing a more effective response. However, progress
translating commitments into improved outcomes for key populations has been hindered
by persistent barriers, such as stigma (including self‐stigma), discrimination, and
punitive legal and policy environments. In addition, the field faces ever‐present
data challenges with key populations, who often do not self‐disclose their current
or former status as key population members. Consequently, they may be included as
members of the “general population” and their contribution to HIV transmission underreported
and unrecognized. Alternatively, they may be connected to key population community
services in one place but receive testing or treatment services anonymously in another,
making it difficult for programmes to track and support clients across multiple service
The limited population‐based data that are available show that testing and treatment
coverage among key populations remains disproportionately low with no key population
group close to achieving 90‐90‐90 targets 1, 16. This has led to calls for improving
outcomes for key populations through data‐driven interventions. Indeed, this supplement
grew out of the urgent need to share the emerging evidence from both new and evolving
service delivery interventions for key populations.
The HIV prevention, care and treatment cascade has been globally adopted as a useful
framework for guiding key population programming (Figure 1) 8. It can indicate where
programmatic efforts are falling short in reaching and retaining key populations across
the continuum of care, and thereby pinpoint areas for intensified work. Moreover,
this cascade model highlights the importance of engaging and building capacity of
communities to lead efforts to reach, test, treat, and retain key populations in services,
as well as the need to tackle structural barriers – including stigma, discrimination,
violence, gender‐based bias and, in many cases, criminalization. Cutting across the
cascade is the need to ensure programmatic efforts are rights based and that confidentiality,
safety and security are respected.
Cascade of HIV prevention, care, and treatment services for key populations
Achieving epidemic control will not be possible without more robust and rapid progress
in delivering evidence‐based interventions that improve key populations’ access to
and uptake of HIV services across the cascade. Fundamental to that progress is the
generation and use of key population‐specific cascade data. The recently relaunched
Key Populations Atlas from UNAIDS represents an important step in that direction 17.
This tool brings together country‐specific data on a variety of indicators disaggregated
by key population group. We need to complement this with better data from a variety
of methodological approaches that identify strategies effective at reaching and engaging
key populations at different points along the HIV cascade, and allow targeted investments
in programming at those points where they are most needed.
Towards a more effective response for key populations
Recognition of these needs has led to advances in monitoring key populations’ uptake
of services across the cascade to identify “leaks” in the system, as well as more
sophisticated analysis and use of data to identify solutions and strengthen programming
18, 19. In addition, a number of key population‐focused implementation science studies
are underway across a range of geographies to evaluate the effectiveness of new approaches,
outreach strategies and delivery modalities in overcoming structural obstacles and
improving service uptake and retention with different key population groups 20.
As programming is scaled up globally, it is critical that we maximize public health
impact by sharing the latest evidence of what works to engage key populations in targeted
prevention, treatment, and retention programmes. The contents of this supplement represent
high‐quality articles from a range of multidisciplinary efforts to advance key population
science and practice across the cascade. They offer new evidence and data‐driven strategies
for improving programming with MSM, sex workers, transgender people and PWID across
diverse geographies. The supplement does not contain articles addressing prisoners
as they require significantly different approaches from key populations in communities
outside incarcerated settings.
Data approaches to improve cascade monitoring
Five of the papers in this supplement describe methods and analyses specific to key
populations that can be used to refine and focus interventions. The data generated
from these approaches are important to guide strategic planning, resource allocation
and programme quality improvement initiatives.
The supplement opens with a commentary by Hakim et al. in which the authors make the
case for why we need better key population cascade data and how we can get it 21.
They argue that targeted bio‐behavioural surveys represent an important source of
data to guide the epidemic response but have been underutilised to monitor and inform
key population service delivery efforts. While there may be sampling concerns and
other limitations to these types of surveys, the authors underscore that bio‐behavioural
survey data are critical to triangulate with available programme data for a comprehensive
assessment of the reach and impact of services for key populations.
An article by Mukandavire et al. presents a new methodology to estimate the contribution
of onward HIV transmission among key populations to the overall HIV dynamic in Dakar,
Senegal 22. They report that the contribution of commercial sex to HIV transmission
is diminishing; however, unprotected sex between men contributed to 42% of transmissions
between 1995 and 2005, and increases to an estimated 64% in the 2015 to 2025 period.
The authors posit that this dynamic may also be observed in other low‐ and middle‐income
countries where the contribution of MSM to overall HIV transmission may be under‐appreciated.
To better refine key population programming at country level, Lillie et al. describe
a partnership between PEPFAR and The Global Fund to conduct key populations cascade
assessments 23. By jointly participating in these assessments, major funders and national
stakeholders are able to better align packages of services, training, geographic coverage,
innovations, data collection and quality improvement efforts. These cascade assessments
were completed in eight countries: Malawi, Cameroon, Swaziland, Haiti, Angola, Nepal,
Cote d'Ivoire and Botswana. For this commentary, the authors review common challenges
and recommendations made at the programme, national and donor level at each step in
Using data collected from an online survey implemented through the gay social networking
application, Hornet, Ayala et al. describe determinants of HIV service uptake among
a global sample of MSM 24. Of the 10,774 HIV‐negative respondents, 13% reported PrEP
use. Among HIV‐positive respondents (n = 1243), both ART use and undetectable viral
load (UVL) were associated with older age, a recent sexually transmitted infection
(STI) test or STI treatment; and awareness of unlikely HIV transmission with UVL.
The findings underscore the importance of STI testing and treatment as well as information
about HIV transmissibility (U = U) for encouraging PrEP and ART use. This study is
noteworthy for its innovative use of a gay dating app to rapidly generate data from
a large online community of MSM that can be used for advocacy and tailored programme
Finally, Suraratcheda et al. contribute the first estimates on the costs and cost‐effectiveness
of providing oral PrEP for MSM in Thailand 25. Costing studies related to key population
programming are extremely limited yet costing data are critical for effective programme
planning. This paper makes an important first contribution for the Asia‐Pacific region
by estimating the annual costs (US$223 to US$331 per MSM per year, including demand
creation activities) and cost‐effectiveness of PrEP under several delivery scenarios.
While providing PrEP to all MSM over the next five years would have greater epidemiological
and economic benefit to Thailand, the authors conclude that providing PrEP to high‐risk
MSM would be the most cost‐effective approach.
Improving recruitment, testing uptake and case finding
The supplement features two articles that broaden our understanding of strategies
for improving the reach of prevention services and uptake of HIV testing among previously
unreached key population members. Herce et al. report data from two bio‐behavioural
surveys in Malawi and Angola that illustrate the value of providing venue‐based outreach
and testing services in “hotspots,” where people including MSM, FSWs and transgender
people meet and seek sex partners 26. Over 70% of the individuals diagnosed with HIV
through the venue‐based approach were not previously aware of their status, indicating
that this was effective at increasing testing uptake and case finding among these
A study by Kan et al. from Tajikistan compares the effectiveness of three network‐based
approaches to recruitment and case finding among PWID 27. The approaches include two
respondent‐driven sampling (RDS) strategies – one restricted and the other unrestricted
– and an active case‐finding (ACF) strategy that involves direct outreach by peers
who are living with HIV or current/former PWID. Collectively, these approaches identified
190 new cases of HIV in an eight‐month period, linked 80% of them to confirmatory
testing, and initiated 87.5% of the confirmed positives on treatment. While RDS strategies
were more effective than ACF in detecting new HIV cases, the ACF approach attracted
a higher proportion of first‐time testers. This finding led the authors to note that
both strategies are likely needed to achieve their case‐finding goals among PWID in
Innovations in HIV testing modalities and linkage to treatment
Recognizing that innovations in HIV testing options are needed to improve coverage,
three articles in the supplement examine feasibility, acceptability, and effectiveness
of new HIV testing modalities. Tun et al. present the results of a pilot intervention
to distribute oral HIV self‐testing kits to MSM through key opinion leaders in Lagos,
Nigeria 28. This study found that not only is oral self‐testing feasible and highly
acceptable among MSM in this urban population, but also that effective linkage to
treatment can be achieved for those who test positive through self‐testing with active
follow‐up and access to a trusted MSM‐friendly community clinic that offers HIV treatment.
In a study from Vietnam, Green et al. explore HIV testing interventions through MSM
lay providers and HIV self‐testing, promoted through online channels and face‐to‐face
interactions 29. The study found that more than half of the MSM who sought lay‐ or
self‐testing were first‐time testers. These new testing strategies resulted in higher
detection of new HIV cases (6.8%) compared to conventional facility‐based testing
(estimated at 1.6%), while those linked to testing from social media interventions
presented with even higher HIV‐positive people (11.6%). Moreover, 90% of those identified
as positive were successfully registered for ART.
A study from Thailand also demonstrates the promise of leveraging technology and self‐testing
to improve reach and testing uptake among MSM and transgender women 30. In this study,
Phanuphak et al. explore preferences among three different modalities of HIV testing
including: (1) offline HIV counselling and testing; (2) online pre‐test counselling
and offline HIV testing; and (3) online counselling and online, supervised, HIV self‐testing.
The study demonstrated that online counselling coupled with online, supervised, HIV
self‐testing is feasible and acceptable. In addition, the online strategy produced
the highest proportion of first time testers (47.3%) and had the highest HIV prevalence
(15.9%). Being a transgender woman and spending more than four hours per day on social
media increased a participant's likelihood to self‐select for online counselling and
Taking community‐led programming across the continuum to scale
Two papers in the supplement report outcomes from large‐scale, key population‐led
efforts to improve outcomes across the cascade. Ndori‐Mharadze et al. report results
from an evaluation of ‘Sisters with a Voice’, Zimbabwe's nationally scaled comprehensive
programme for FSWs, following intensified community mobilization activities 31. The
findings demonstrate that early peer mobilization efforts to familiarize community
members with tailored HIV services were associated with improved outcomes, notably
increases in HIV testing frequency, knowledge of HIV status and increased linkage
Results of an innovative HIV self‐testing component within a broader, community‐wide
implementation science project in Curitiba, Brazil demonstrated feasibility and improved
HIV diagnosis among young MSM who had not previously tested for HIV 32. Based on their
findings, De Boni et al. report on the expansion and tailoring of the Internet‐based
self‐testing platform to increase HIV testing coverage among MSM in São Paulo, Brazil's
largest metropolitan area with the highest number of new HIV infections.
Addressing structural barriers
Due to the criminalized and stigmatized nature of key populations globally, sex workers,
MSM, PWID and transgender people are often afraid to visit healthcare services and,
when they do go, are reluctant to disclose their sexual histories for fear of rejection,
derision or other negative reactions from providers 33, 34. In addition, the perpetration
of violence against key populations is frequent and often severe. Experiences of violence
not only increase the risk of key populations acquiring HIV but also deeply affect
their desire and ability to get tested for HIV and adhere to HIV treatment 35, 36.
Two papers in this supplement address structural barriers to better HIV‐related outcomes.
Bhattacharjee et al. describe successful efforts to integrate violence prevention
and response services into the national key population programme in Kenya 37. Drawing
on programme data over a four‐year period, this paper contributes important evidence
that it is possible to address violence against key populations under the leadership
of the national government, even in an environment where sex work, same‐sex sexual
practices and drug use are criminalized 38.
A commentary by Friedland et al. reflects on the evolution of the PLHIV Stigma Index,
which at the end of 2017 had interviewed more than 100,000 PLHIV in 90 countries 39.
The paper describes efforts at updating the new PLHIV Stigma Index 2.0 to better capture
HIV‐related and key population‐related stigma, within the context of modern global
testing and treatment guidelines. The updated tool was pilot‐tested through a community‐led
process in Cameroon, Senegal and Uganda, and provides essential evidence and opportunities
for communities in other countries to more effectively document stigma and advocate
for and implement stigma mitigation interventions as part of human rights‐affirming
These papers provide much‐needed contributions to the evidence base for key population
programming across the HIV prevention, care and treatment cascade. Our hope is that
this supplement will compel funders, policymakers, implementers and other stakeholders
to do more now to champion data‐driven programming. One common theme that emerges
from this supplement is that we should establish and scale‐up innovative, community‐led
services, while expanding the integration and options for key populations within the
health system. In addition, we will not make sustainable improvements in outcomes
if we do not better address the stigma, discrimination and violence that key populations
experience at the hands of family, community members, health care providers and the
As more evidence on key population programmes emerges, it is critical that the international
community catalyse these advances with supportive policies that promote widespread
uptake of effective approaches. Important studies are ongoing through the PEPFAR Key
Populations Implementation Science and amfAR Implementation Science Grants initiatives,
from which we anticipate more rich data designed to fill further gaps in our understanding
of how to implement better services for key populations.
After more than three decades in the fight against HIV, plans to end the HIV epidemic
through goals such as UNAIDS 90‐90‐90 have been adopted by governments, major donors,
and stakeholders globally. Investments to address the epidemic among key populations
should be central to these efforts. With ever‐present threats of stigma, discrimination,
violence, and other human rights abuses, the gains that have been made among key populations
are precarious. The urgency of continuing to maintain focus on these groups cannot
be understated. To leave no one behind, the substantial progress that has been made
to date against the epidemic will need to be bolstered with rigorous, key population‐specific
data collection and use, with partnerships focused on vigilance, courage, tolerance
The authors have no other funding or conflicts of interest to disclose.
RCW, TB, GM and RW all contributed to the preparation of the first draft. All authors
approved the final manuscript.
This manuscript was supported by multiple agencies including the United States Agency
for International Development (USAID) and the U.S. President's Emergency Plan for
AIDS Relief (PEPFAR) through the Linkages across the Continuum of HIV Services for
Key Populations Affected by HIV project (LINKAGES, Cooperative Agreement AID‐OAA‐A‐14‐00,045);
PEPFAR through the Centers for Disease Control and Prevention (CDC); and amfAR, the
Foundation for AIDS Research. The content is solely the responsibility of the authors
and does not necessarily represent the official views of any of the funding agencies.