Revealing geographical and population heterogeneity in HIV incidence, undiagnosed HIV prevalence and time to diagnosis to improve prevention and care: estimates for France

Introduction: to close gaps in HIV prevention and care, knowledge about locations and populations most affected by HIV is essential. Here, we provide subnational and subpopulation estimates of three key HIV epidemiological indicators, which have been unavailable for most settings. Methods: we used surveillance data on newly diagnosed HIV cases from 2004 to 2014 and backcalculation modelling to estimate in France, at national and subnational levels, by exposure group and country of birth: the numbers of new HIV infections, the times to diagnosis, the numbers of undiagnosed HIV infections. The denominators used for rate calculations at national and subnational levels were based on population size (aged 18 to 64) estimates produced by the French National Institute of Statistics and Economic Studies and the latest national surveys on sexual behaviour and drug use. Results: we estimated that, in 2014, national HIV incidence was 0.170 (95% confidence intervals (CI): 0.16 to 0.18) or 6607 (95% CI: 6057 to 7196) adults, undiagnosed HIV prevalence was 0.640 (95% CI: 0.57 to 0.70) or 24,197 (95% CI: 22,296 to 25,944) adults and median time to diagnosis over the 2011 to 2014 period was 3.3 years (interquartile range: 1.2 to 5.7). Three mainland regions, including the Paris region, out of the 27 French regions accounted for 56% of the total number of new and undiagnosed infections. Incidence and undiagnosed prevalence rates were 2 to 10fold higher than the national rates in three overseas regions and in the Paris region (pvalues < 0.001). Rates of incidence and undiagnosed prevalence were higher than the national rates for the following populations (pvalues < 0.001): bornabroad men who have sex with men (MSM) (respectively, 108 and 78fold), Frenchborn MSM (62 and 44fold), bornabroad persons who inject drugs (14 and 18fold), subSaharan Africanborn heterosexuals (women 15 and 15fold, men 11 and 13fold). Importantly, affected populations varied from one region to another, and in regions apparently less impacted by HIV, some populations could be as impacted as those living in most impacted regions. Conclusions: in France, some regions and populations have been most impacted by HIV. Subnational and subpopulation estimates of key indicators are not only essential to adapt, design implement and evaluate tailored HIV interventions in France, but also elsewhere where similar heterogeneity is likely to exist.