Multiple introductions and onward transmission of HIV-1 subtype B strains in Shanghai, China.

OBJECTIVE: To investigate the viral genetic evolution, spatial origins and patterns of transmission of HIV-1 subtype B in Shanghai, China.

METHODS: A total of 242 Shanghai subtype B and 1519 reference pol sequences were subjected to phylogenetic inference and genetic transmission network analyses.

RESULTS: Phylogenetic analysis revealed that subtype B strains circulating in Shanghai were genetically diverse and closely associated with viral sequence lineages in Beijing (76 of 242 [31.4%]), Central China (Henan/Hebei/Hunan/Hubei) (43 of 242 [17.8%]), Chinese Taiwan (20 of 242 [8.3%]), Japan (6 of 242 [2.5%]), and Korea (7 of 242 [2.9%]), suggesting multiple introductions into Shanghai from mainland China and Taiwan, Japan, and Korea. Interestingly, a monophyletic Shanghai lineage (SH-L) (36 of 242 [14.9%]) of HIV-1 subtype B most likely originated from an Argentine strain, transferred through Liaoning infected individuals. In-depth analyses of 195 Shanghai subtype B sequences revealed that a total of 37.9% (n = 74) sequences contributed to 35 transmission networks, whereof 33.8% (n = 25) of the sequences associated with infected individuals from other provinces.

CONCLUSIONS: Our new findings reflect the evolution complexity and transmission dynamics of HIV-1 subtype B in Shanghai, which would provide critical information for the design of effective prevention measures against HIV transmission.