Similar but different: Integrated phylogenetic analysis of Austrian and Swiss HIV-1 sequences reveal differences in transmission patterns of the local HIV-1 epidemics. JAIDS
Kusejko et al. compared HIV transmission dynamics and studied the role of international HIV transmission using phylogenetic analyses in the Swiss and the Austrian HIV Cohort Studies (SHCS and AHVICOS).
Data from the drug resistance databases of the two cohorts as well as the international Los Alamos HIV sequence database were used to create phylogenetic pairs (so-called “cherries”) which were categorized as follows: domestic cherries included 2 patients from the same cohort, international cherries included one patient from SHCS or AHVICOS and one patient from the international Los Alamos database, and SHCS/AHVICOS cherries included patients from both SHCS and AHVICOS.
The authors included 3’141 individuals from AHIVCOS and 12’902 from the SHCS. Patient characteristics from the two cohorts were very similar (73% male, 41% men who have sex with men (MSM), and 73% were sequenced prior to any antiretroviral therapy. Individuals were predominantly in domestic (SHCS 43.0%, AHIVCOS 36.5%) and international cherries (SHCS 8.2%, AHIVCOS 8.3%), and 220 patients formed SHCS/AHIVCOS cherries, reflecting 1.7% of the SHCS and 7.0% of the AHIVCOS population. The international transmissions were driven by MSM in Austria and heterosexual individuals in Switzerland, whereas transmission among intravenous drug users mainly occurred in local transmission networks.
In summary, the present study shows that international transmission plays an essential role in the HIV epidemics in Switzerland and Austria. This work highlights the importance of international collaborations to understand transmission patterns and guide HIV prevention efforts.