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

•HIV-1 subtype B genetic diversity in Shanghai was due to multiple introductions.•Japan and Korea subtype B have become the source of international dissemination.•HIV-1 subtype Thai-B strain has spread among the MSM population in Shanghai.•A unique Shanghai subtype B lineage most likely originated from Argentina.•Among 35 networks, one third of the Shanghai infections were linked to those in other provinces.

SummaryObjectiveTo investigate the viral genetic evolution, spatial origins and patterns of transmission of HIV-1 subtype B in Shanghai, China.MethodsA total of 242 Shanghai subtype B and 1519 reference pol sequences were subjected to phylogenetic inference and genetic transmission network analyses.ResultsPhylogenetic 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.ConclusionsOur 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.