Spatio-temporal estimates of HIV risk group proportions for adolescent girls and young women across 13 priority countries in sub-Saharan Africa

The Global AIDS Strategy 2021-2026 identifies adolescent girls and young women (AGYW) as a priority population for HIV prevention, and recommends differentiating intervention portfolios geographically based on local HIV incidence and individual risk behaviours. We estimated prevalence of HIV risk behaviours and associated HIV incidence at health district level among AGYW living in 13 countries in sub-Saharan Africa. We analysed 46 geospatially-referenced national household surveys conducted between 1999-2018 across 13 high HIV burden countries in sub-Saharan Africa. Female survey respondents aged 15-29 years were classified into four risk groups (not sexually active, cohabiting, non-regular or multiple partner[s] and female sex workers [FSW]) based on reported sexual behaviour. We used a Bayesian spatio-temporal multinomial regression model to estimate the proportion of AGYW in each risk group stratified by district, year, and five-year age group. Using subnational estimates of HIV prevalence and incidence produced by countries with support from UNAIDS, we estimated new HIV infections in each risk group by district and age group. We then assessed the efficiency of prioritising interventions according to risk group. Data consisted of 274,970 female survey respondents aged 15-29. Among women aged 20-29, cohabiting (63.1%) was more common in eastern Africa than non-regular or multiple partner(s) (21.3%), while in southern countries non-regular or multiple partner(s) (58.9%) were more common than cohabiting (23.4%). Risk group proportions varied substantially across age groups (65.9% of total variation explained), countries (20.9%), and between districts within each country (11.3%), but changed little over time (0.9%). Prioritisation based on behavioural risk, in combination with location- and age-based prioritisation, reduced the proportion of population required to be reached in order to find half of all expected new infections from 19.4% to 10.6%. FSW were 1.3% of the population but 10.6% of all expected new infections. Our risk group estimates provide data for HIV programmes to set targets and implement differentiated prevention strategies outlined in the Global AIDS Strategy. Successfully implementing this approach would result in more efficiently reaching substantially more of those at risk for infections.

Progress towards 2020 global HIV impact and treatment targets

INTRODUCTION

Over the past 20 years, the response to the HIV epidemic has achieved remarkable results. These results have often been motivated by targets adopted by countries through United Nations (UN) Political Declarations on HIV. The 2016 political declaration included two impact targets, to achieve a 75% decline in new HIV infections and AIDS-related deaths between 2010 and 2020, and to reach the 90-90-90 testing and treatment targets by 2020. Our objective is to summarize progress towards these targets using robust and comparable HIV estimates released by UNAIDS in July 2021. In addition, we comment on the importance of targets and the modelled estimates required to quantify those targets.

DISCUSSION

The UNAIDS estimates indicate that at the global and regional levels, the 2020 targets were missed: new infections declined by 31% and AIDS-related deaths declined by 47% between 2010 and 2020, compared to a target of 75% decline for both indicators. Similarly, no region achieved the 90-90-90 testing and treatment targets. Some countries, in diverse settings, achieved these targets showing that the targets were not overly ambitious if the right funding, policies and evidence-informed interventions at the right scale were in place. The 2021 UN Political Declaration on HIV, adopted on 8 June 2021, has set out a new set of ambitious but achievable targets for 2025. The 2025 targets and the required actions to reach those targets are described in the Global AIDS Strategy 2021-2026, which provides a framework to reprioritize HIV responses by reducing inequalities and building on the achievements of multiple Sustainable Development Goals. The Strategy encourages countries to monitor progress against targets for different geographic areas and populations to maximize equitable services and ensure accountability and also to understand why targets are being missed.

CONCLUSIONS

The UNAIDS epidemiological estimates provide information that promote accountability and estimate progress towards global targets at the national level. Additional strategic information and analyses are required to identify the populations that are furthest from the targets and the programmes and policies that are keeping countries from meeting their targets.

Naomi: a new modelling tool for estimating HIV epidemic indicators at the district level in sub-Saharan Africa

INTRODUCTION

HIV planning requires granular estimates for the number of people living with HIV (PLHIV), antiretroviral treatment (ART) coverage and unmet need, and new HIV infections by district, or equivalent subnational administrative level. We developed a Bayesian small-area estimation model, called Naomi, to estimate these quantities stratified by subnational administrative units, sex, and five-year age groups.

METHODS

Small-area regressions for HIV prevalence, ART coverage and HIV incidence were jointly calibrated using subnational household survey data on all three indicators, routine antenatal service delivery data on HIV prevalence and ART coverage among pregnant women, and service delivery data on the number of PLHIV receiving ART. Incidence was modelled by district-level HIV prevalence and ART coverage. Model outputs of counts and rates for each indicator were aggregated to multiple geographic and demographic stratifications of interest. The model was estimated in an empirical Bayes framework, furnishing probabilistic uncertainty ranges for all output indicators. Example results were presented using data from Malawi during 2016-2018.

RESULTS

Adult HIV prevalence in September 2018 ranged from 3.2% to 17.1% across Malawi's districts and was higher in southern districts and in metropolitan areas. ART coverage was more homogenous, ranging from 75% to 82%. The largest number of PLHIV was among ages 35 to 39 for both women and men, while the most untreated PLHIV were among ages 25 to 29 for women and 30 to 34 for men. Relative uncertainty was larger for the untreated PLHIV than the number on ART or total PLHIV. Among clients receiving ART at facilities in Lilongwe city, an estimated 71% (95% CI, 61% to 79%) resided in Lilongwe city, 20% (14% to 27%) in Lilongwe district outside the metropolis, and 9% (6% to 12%) in neighbouring Dowa district. Thirty-eight percent (26% to 50%) of Lilongwe rural residents and 39% (27% to 50%) of Dowa residents received treatment at facilities in Lilongwe city.

CONCLUSIONS

The Naomi model synthesizes multiple subnational data sources to furnish estimates of key indicators for HIV programme planning, resource allocation, and target setting. Further model development to meet evolving HIV policy priorities and programme need should be accompanied by continued strengthening and understanding of routine health system data.

Trends in knowledge of HIV status and efficiency of HIV testing services in sub-Saharan Africa, 2000-20: a modelling study using survey and HIV testing programme data

BACKGROUND

Monitoring knowledge of HIV status among people living with HIV is essential for an effective national HIV response. This study estimates progress and gaps in reaching the UNAIDS 2020 target of 90% knowledge of status, and the efficiency of HIV testing services in sub-Saharan Africa, where two thirds of all people living with HIV reside.

METHODS

For this modelling study, we used data from 183 population-based surveys (including more than 2·7 million participants) and national HIV testing programme reports (315 country-years) from 40 countries in sub-Saharan Africa as inputs into a mathematical model to examine trends in knowledge of status among people living with HIV, median time from HIV infection to diagnosis, HIV testing positivity, and proportion of new diagnoses among all positive tests, adjusting for retesting. We included data from 2000 to 2019, and projected results to 2020.

FINDINGS

Across sub-Saharan Africa, knowledge of status steadily increased from 5·7% (95% credible interval [CrI] 4·6-7·0) in 2000 to 84% (82-86) in 2020. 12 countries and one region, southern Africa, reached the 90% target. In 2020, knowledge of status was lower among men (79%, 95% CrI 76-81) than women (87%, 85-89) across sub-Saharan Africa. People living with HIV aged 15-24 years were the least likely to know their status (65%, 62-69), but the largest gap in terms of absolute numbers was among men aged 35-49 years, with 701 000 (95% CrI 611 000-788 000) remaining undiagnosed. As knowledge of status increased from 2000 to 2020, the median time to diagnosis decreased from 9·6 years (9·1-10) to 2·6 years (1·8-3·5), HIV testing positivity declined from 9·0% (7·7-10) to 2·8% (2·1-3·9), and the proportion of first-time diagnoses among all positive tests dropped from 89% (77-96) to 42% (30-55).

INTERPRETATION

On the path towards the next UNAIDS target of 95% diagnostic coverage by 2025, and in a context of declining positivity and yield of first-time diagnoses, disparities in knowledge of status must be addressed. Increasing knowledge of status and treatment coverage among older men could be crucial to reducing HIV incidence among women in sub-Saharan Africa, and by extension, reducing mother-to-child transmission.

FUNDING

Steinberg Fund for Interdisciplinary Global Health Research (McGill University); Canadian Institutes of Health Research; Bill & Melinda Gates Foundation; Fonds the recherche du Québec-Santé; UNAIDS; UK Medical Research Council; MRC Centre for Global Infectious Disease Analysis; UK Foreign, Commonwealth & Development Office.

Use of geographic and genotyping tools to characterise tuberculosis transmission in Montreal

SETTING

In Canada, tuberculosis (TB) is increasingly an urban health problem. Montreal is Canada's second-largest city and the second most frequent destination for new immigrants and refugees.

OBJECTIVES

To detect spatial aggregation of cases, areas of excess incidence and local 'hot spots' of transmission in Montreal.

DESIGN

We used residential addresses to geocode active TB cases reported on the Island of Montreal in 1996-2000. After a hot spot analysis suggested two areas of overconcentration, we conducted a spatial scan, with census tracts (population 2500-8000) as the primary unit of analysis and stratification by birthplace. We linked these analyses with genotyping of all available Mycobacterium tuberculosis isolates, using IS6110-RFLP and spoligotyping.

RESULTS

We identified four areas of excess incidence among the foreign-born (incidence rate ratios 1.3-4.1, relative to the entire Island) and one such area among the Canadian-born (incidence rate ratio 2.3). There was partial overlap with the two hot spots. Genotyping indicated ongoing transmission among the foreign-born within the largest high-incidence zone. While this zone overlapped the area of high incidence among Canadian-born, genotyping largely excluded transmission between the two groups.

CONCLUSIONS

In a city with low overall incidence, spatial and molecular analyses highlighted ongoing local transmission.

Dwellings, crowding, and tuberculosis in Montreal

The association of tuberculosis (TB) with poverty has long been recognized, yet it may reflect not only characteristics of poor individuals, but also housing and neighborhood features which promote airborne spread. We sought to determine whether dwelling and building features, residential density and crowding are independently associated with TB occurrence in a low-incidence setting. We used residential addresses to geocode active TB cases reported in Montreal in 1996-2000. These "case dwellings" were linked to the municipal dwelling geodatabase from 2000, and to Canadian census data from 1996. We compared them with randomly selected Montreal dwellings ("controls," in a 1:10 ratio), using the same data sources. From multivariate logistic regression, the 595 case dwellings were more likely than the 5950 control dwellings to be in buildings >5 stories tall (adjusted odds ratios [OR] 1.6; 95% CI: 1.0-2.5), constructed since 1970 (adjusted OR 2.5; 1.8-3.6), in the lowest quartile for resale valuation (adjusted OR 1.3; 1.0-1.6), and on blocks where lot coverage exceeded the median value (adjusted OR 1.3; 1.0-1.6). Case dwellings were also more often found in census tracts with more persons per room, and a higher proportion of inhabitants who had arrived in Canada within the last 5 years. We conclude that dwelling and building features-notably dwellings in taller and new buildings, with lower resale value, and dwellings on blocks with high residential density-as well as crowding, were associated with TB occurrence, after adjustment for sociodemographic factors.