Background
Late presentation remains an important hurdle in the management and prevention of HIV infection. Our aim was to investigate the potential source of infection among people living with HIV (PLHIV) with different stages of diagnosis, using in addition to the traditional definition for late diagnosis, the time interval between HIV acquisition and diagnosis dates.
Methods
The study sample consisted of 3,093 HIV-1 subtype A1 and B sequences from a period with dense sampling in Greece. Analysis was performed on 2,385 sequences with pairwise genetic distances <0.015 substitutions/site. 2,194 PLHIV were categorized according to CD4 count at diagnosis (advanced disease: CD4<200 cells/μl or clinical AIDS, late: 200≤CD4≤350 cells/μl, non-late: CD4>350 cells/μl). Treatment-naïve PLHIV were categorized according to the time from HIV infection to diagnosis (recent: 0.07-1.20, intermediate: 1.21-2.55, late: 2.56-11.71 years). HIV infection was estimated by molecular clock analysis. HIV transmissions among PLHIV with different diagnosis status were estimated by a modified statistical phylogeography method.
Results
For subtype A1, analysis using the estimated infection dates revealed that among PLHIV with recent diagnosis, the mean number of infections originated from PLHIV with late and intermediate diagnosis were 35.7 (11%) and 32.8 (10%), respectively. For those diagnosed late, only 21.3 (6.7%) and 18.5 (5.8%) of infections were from PLHIV with intermediate and early diagnosis. Similarly for subtype B, a proportion of infections among PLHIV with recent (13%) and intermediate (17.5%) diagnoses originated from PLHIV with late status. Statistical phylogeography confirmed that late presenters were a significant source of HIV transmission to PLHIV from other groups. Analysis using CD4 counts showed consistent results for both subtypes. Late and advanced disease groups provided a significant source of infections to other groups. Non-late presenters were not a significant source of HIV transmission to those with late presentation and advanced disease.
Conclusions
Using two different definitions for late diagnosis, we showed that PLHIV diagnosed at a late stage provide a source of infection to those diagnosed earlier, in Greece. 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.