Transmission dynamics and molecular characterization of HIV-1 epidemic among therapeutic failure patients in Santa Catarina state, southern Brazil.

The HIV-1 epidemic in southern Brazil is mostly caused by subtype C, which contrasts the dominance of subtype B in the other regions of the country. Santa Catarina (SC), although the smallest state in the southern region, presents one of the highest incidences and mortality rates in Brazil due to AIDS. This work investigated the HIV-1 molecular diversity and phylogenetic transmission networks in SC state by analyzing a database of 3070 sequences of the national genotyping service. HIV-1C proved to be the most frequent subtype, with a significant increase in prevalence over time. HIV-1B was observed to be associated with highly educated men, suggesting a compartmentalization from other subtypes. Such observation was confirmed by the high frequency of HIV-1B circulating in MSM transmission networks. Identified transmission clusters were majority composed by individuals living up to 25 km away and interstate linkages were mainly between southern neighbor states. In general, individuals between 25 and 40 years old and sequences sampled after 2014 were more likely to be in transmission chains, in agreement with the universal treatment protocol launched in 2014. The present study brings new insights about HIV-1 transmission dynamics in southern Brazil.