Identification of risk factors associated with national transmission and late presentation of HIV-1 in Denmark, 2009-2017

Background Despite availability of pre-exposure prophylaxis, the incidence of HIV-1 in Europe remained stable the past decade. Reducing the burden of new HIV-1 infections requires more evidence on persistent transmissions and risk profiles of high-risk transmitters and late presenters (LP). Aim This study investigates risk factors associated with HIV-1-transmission clusters and late presentation with HIV-1 in Denmark. Methods: Blood samples and epidemiological information were collected from newly HIV-1 diagnosed patients in Denmark between 2009 and 2017. POL genes were genotyped and phylogenetic analyses were performed to identify clusters. Risk factors for clustering and LP were investigated with partial proportional odds and logistic regression. Covariates included transmission mode, HIV-1 subtype, age at sample collection, ethnicity, and cluster activity. Results: We included 1040 individuals in the analysis with 59.6% identified as subtype B and 48.4% in a cluster. Risk factors for clustering included Danish origin (odds ratio (OR): 2.95, 95% confidence interval (CI): 2.21-3.96), non-LP (OR: 1.44, CI: 1.12-1.86), and MSM. Increasing age and nonsubtype B decreased risk (OR: 0.69, CI: 0.50-0.94). Risk for LP was lower for active clusters (OR: 0.60, CI: 0.44-0.82) and Danish ethnicity (OR: 0.43, CI: 0.27-0.67). NonDanish MSM had a lower risk than non-Danish heterosexuals (OR: 0.34, CI: 0.21-0.55). Conclusion: As HIV-1 transmission in Denmark is driven by early diagnosed, younger, subtype B-infected MSM, they may benefit most from PrEP. Non-Danish heterosexuals outside active clusters are most at risk for LP, and could benefit from improved communication and information to achieve earlier diagnosis and treatment.