FIGURE 1.

Phylogenetic tree analyses identifying 3 distinct HIV-1 phylogenetic clusters unique to MSM in China; neighbor-joining trees of 1.0-kb pol gene (HXB₂: 2253–3278 nt), representing the CRF01_AE genotype (A), the CRF07_BC genotype (B), and the subtype B/B′ (C). Individual sequences are indicated by symbols corresponding to their known risk groups: MSM (circle), heterosexual (triangle), IDU (square), former plasma donor (FPD) (inverted triangle), and unknown high-risk behavior (diamond). The geographic origin of each sequence is color-coded (see inset). For panels A–C, we selected as many sequences as possible from regions with smaller sample sizes and only a few phylogenetically representative sequences from large-sample regions such as Shenyang, Beijing, and Chengdu for simplicity. These selected sequences are shown together with reference sequences previously identified in other high-risk populations in China and its neighboring countries (only IDs of reference sequences are shown in trees) and with subtype reference sequences from the Los Alamos HIV sequences database (http://hiv-web.lanl.gov/content/index). The bootstrap values of the 1000 replicates are labeled on the major branches.