CD4 and sexually transmitted disease: This study indicated that aged 25–49 years, cadre/staff/teacher, unmarried, minority, high school or below, initial CD4 counts >500 cells/μL, no STD history, homosexual partners ≥10, special survey, long-term infection, and drug resistance were associated with clustering in molecular transmission networks, and clustering frequency in this population was significantly related to CD4 counts, year and city.