Quantifying the Evolving Contribution of HIV Interventions and Key Populations to the HIV Epidemic in Yaoundé, Cameroon

Abstract

Background: Key populations (KP) including men who have sex with men (MSM), female sex workers (FSW), and their clients are disproportionately affected by HIV in Sub-Saharan Africa. We estimated the evolving impact of past interventions and contribution of unmet HIV prevention/treatment needs of KP and lower-risk groups to HIV transmission.Setting: Yaoundé, Cameroon. Methods:We parametrised and fitted a deterministic of HIV transmission model to Yaoundé-specific demographic, behavioural, HIV and intervention coverage data in a Bayesian framework. We estimated the fraction of incident HIV infections averted by condoms and antiretroviral therapy (ART) and the fraction of all infections over 10-year periods directly and indirectly attributable to unprotected sex within and between each risk group. Results: Condom use and ART together may have averted 43% (95% uncertainty interval: 31-54) of incident infections over 1980-2018 and 72% (66-79) over 2009-2018. Most onward transmissions over 2009-2018 stemmed from unprotected sex between lower-risk individuals (47% (32-61)), clients (37% (23-51)), and MSM (35% (20-54)) with all their partners. The contribution of commercial sex decreased from 25% (8-49) over 1989-1998 to 8% (3-22) over 2009-2018, due to higher intervention coverage among FSW. Conclusion: Condom use and recent ART scale-up mitigated the HIV epidemic in Yaoundé and changed the contribution of different partnerships to onward transmission over time. Findings highlight the importance of prioritizing HIV prevention and treatment for MSM and clients of FSW whose unmet needs now contribute most to onward transmission, while maintaining services which successfully reduced transmissions in the context of commercial sex.

Costs and Scale-Up Costs of Integrating HIV Self-Testing Into Civil Society Organisation-Led Programmes for Key Populations in Côte d'Ivoire, Senegal, and Mali

“…Recent modelling studies in Cameroon, Senegal, Côte d'Ivoire, and South Africa show that key populations and their sexual partners, particularly FSW and their clients, can play an important role in HIV transmission in both low and high HIV prevalence settings due to prevention gaps ( 3 , 4 , 48 ). HIV prevention and treatment strategies targeting these groups are essential for controlling the HIV epidemic and are likely to provide good value for money.…”

Assessing the Potential Impact of Disruptions Due to COVID-19 on HIV Among Key and Lower-Risk Populations in the Largest Cities of Cameroon and Benin

“…Each risk group could form heterosexual noncommercial (main and casual) partnerships. In the Yaoundé model, FSW could form sexual partnerships with all male groups, 43 , 61 but commercial sex with clients only, whereas they could only form partnerships with clients in the Cotonou model, because of lower reported numbers of noncommercial sex acts by FSW in Cotonou, and the high proportion of seasonal migrants in this group (see Figures 1a, 7, Supplemental Digital Content, http://links.lww.com/QAI/B630 ). The Yaoundé model also included younger (aged 15–24 years) and older (aged 25–49 years) MSM because of their very high HIV prevalence.…”

Estimating the epidemic consequences of HIV prevention gaps among key populations

“…For example, appraisals have been used to help guide prioritization of subgroups for tailored interventions via the strategic design of programmes and services [1,4]. Over the past four decades, there has been an evolution in appraisals from classifications of epidemic type [5] and estimates of who acquires new infections [6], to transmission modelling specifically designed to characterize local transmission dynamics (or sources of transmission) and more explicitly consider underserved populations [7‐15]. This evolution coincided with a growing call to increase the specificity of the HIV response, moving from largely uniform strategies to prioritization with tailored strategies to address unmet HIV prevention and treatment needs (prevention gaps) across subgroups [16‐21].…”

“…At the same time, transmission models have also been specifically designed and used for local HIV epidemic appraisals, an objective that is distinct yet complementary to modelling the impact or efficiency of interventions. For example, between 2010 and 2020, at least eight published studies examined and explicitly reported estimates of onward transmission stemming from the prevention gaps across subgroups in sub‐Saharan Africa [7‐14]. The studies simulated the causal pathway from the unmet needs among a relatively few to population‐level transmission via chains of transmission over sexual networks.…”

“…The studies simulated the causal pathway from the unmet needs among a relatively few to population‐level transmission via chains of transmission over sexual networks. The studies found that 19% to 40% and 4% to 64% of onward transmission over a ten‐year time‐horizon, after at least 2005, stem from unmet HIV prevention and treatment needs among female sex workers (FSW) and men who have sex with men respectively [7‐14]. These estimates of onward transmission risks have been referred to as the transmission population attributable fraction over time (tPAF t ), which quantify the epidemic consequences of the prevention gaps among subgroups.…”