Changing trends in international versus domestic HCV transmission in HIV-positive MSM: A perspective for the DAA scale-up era. Â Â Journal of Infectious Disease
Salazar-Vizcaya et al. aimed to classify hepatitis C virus (HCV) infections in HIV-positive men who have sex with men (MSM) in Switzerland as domestically or internationally acquired, and to estimate how this classification changed over time.
The authors sequenced HCV subtype 1a genomes from 99 persons enrolled in the Swiss HIV Cohort Study and diagnosed with replicating HCV infections. Sixty-six of these sequences were from MSM. They inferred maximum-likelihood phylogenetic trees and time trees containing a fragment of the NS5B region of these and 374 circulating strains. They inferred transmission clusters from these trees and used the country composition of such clusters to attribute infections to domestic or international transmission.
Of HCV transmissions, 50% to 80% were classified as domestic depending on the classification criterion. Between 2000 and 2007, the fraction attributable to domestic transmission was 54% (range 0%–75%). It increased to 85% (range 67%–100%) between 2008 and 2016. The authors found no significant trace of transmission bridging from persons who became infected with HIV through drug injection and MSM within Switzerland, suggesting that the HCV epidemics in these 2 HIV transmission groups are likely disconnected.
In conclusion, this molecular epidemiological study suggests that both international and local transmission have played major roles in the Swiss epidemic of HCV among HIV-positive MSM, and that, while international transmission persists, Swiss domestic transmission has gained importance over time.