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

BACKGROUND: Despite availability of pre-exposure prophylaxis (PrEP), the incidence of HIV-1 in Europe remained stable the past decade. Reduction of new HIV-1 infections requires more knowledge about the profiles of high-risk transmitters and late presenters (LP). AIM: We aimed to investigate 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 diagnosed HIV-1 patients between 2009 and 2017. We genotyped pol genes and performed phylogenetic analyses 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, origin and cluster activity. RESULTS: We included 1,040 individuals in the analysis, 59.6% identified with 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; 95% CI: 1.12–1.86), and men who have sex with men (MSM). Increasing age and non-B subtype infection decreased risk (OR: 0.69; 95% CI: 0.50–0.94). Risk for late presentation was lower for active clusters (OR: 0.60; 95% CI: 0.44–0.82) and Danish origin (OR: 0.43; 95% CI: 0.27–0.67). Non-Danish MSM had a lower risk than non-Danish heterosexuals (OR: 0.34; 95% CI: 0.21–0.55). CONCLUSION: HIV-1 transmission in Denmark is driven by early diagnosed, young, subtype B infected MSM. These may benefit most from PrEP. Non-Danish heterosexual HIV-1 patients could benefit from improved communication to achieve earlier diagnosis and treatment.