Tracing the patterns of HIV-1 transmission among people with different diagnosis status in Greece.

Late presentation remains a major hurdle for HIV management and prevention. We investigated the potential source of transmission among people living with HIV (PLHIV) with different stages of diagnosis, using a combined approach of the traditional definition of late presentation (CD4-based) and the estimated time between HIV acquisition and diagnosis. The study included 3,093 HIV-1 subtype A1 and B sequences from a period with dense sampling in Greece. HIV acquisition dates were estimated using molecular clock analysis and transmissions patterns were assessed with a modified phylogeographic approach. For subtype A1, analysis using the estimated time from HIV acquisition to diagnosis revealed that among PLHIV with recent diagnosis, the mean number of infections originating from PLHIV with late and intermediate diagnosis, were 35.7 (11%) and 32.8 (10.2%), respectively. For those diagnosed late, 21.3 (6.7%) and 18.5 (5.8%) infections (mean number) were from PLHIV with intermediate and recent diagnosis, respectively. Similarly for subtype B, a considerable proportion of infections among PLHIV with recent (12.2%) and intermediate (13.1%) diagnoses originated from PLHIV with late status. Statistical phylogeography confirmed that late presenters were a significant source of transmission to PLHIV in other diagnosis-status categories for both subtypes. Analysis using CD4 cell count showed that late presentation and advanced disease groups provided a significant source of transmission to other groups. Our study highlights that early diagnosis, besides the beneficial effect for the disease prognosis, would significantly mitigate onward HIV transmission. This underscores the need to enhance HIV testing strategies in Greece to ensure earlier diagnosis and timely treatment initiation.