Wertheim, J.O., Brown, A.J.L., Hepler, N.L., et al. Journal of Infectious Diseases (October 2013), E-publication ahead of print.
To characterize the current global HIV-1 transmission network, the authors applied a network approach by constructing HIV-1 transmission clusters using close genetic links to identify potential transmission partners. Clusters were defined as connected groups of potential transmission partners. The global transmission network included all published HIV-1 sequences (n=84,527), representing 141 countries or regions, and incorporated expanded known transmission clusters and previous transmission clusters not considered in the global context. The analysis showed the contemporary pattern of HIV-1 transmission across international borders, with “local” epidemics often including international transmission links; individuals from 72 of the 106 countries or regions represented in transmission clusters had a potential transmission partner from another country. Furthermore, nearly 23 percent of potential transmission partners were from different countries, likely associated with the interconnectedness of larger, international transmission networks. The current network appears to have been established by the early 2000s. The authors argued that analysis at the global scale is critical for assessing the scope of transmission clusters, and should be standard practice. They suggested that using this approach with HIV surveillance data would yield a more robust analysis, and concluded that the global-network approach enables researchers to determine, nearly in real-time, if newly isolated HIV-1 sequences occur in known transmission clusters.