To identify the transmission relationship between HIV infection cases the non-marital non-commercial heterosexual contact in Zhejiang Province.

When HIV positive was informed during January 2020 to January 2022, the staff conducted an epidemiological investigation to collect cases information on sociodemographic characteristics, mobility information, past HIV testing history, high-risk sexual behaviors, sexual partners, and etcetera. At the same time, 6-8 ml of blood from the new diagnosis of people infected with HIV before antiviral treatment was collected to separate the bleeding plasma. pol gene was amplified by nucleic acid extraction and PCR, sequenced by Sequencer 5.0 software, and Cytoscape 3.6.0 software was used to draw HIV molecular transmission network.

From January 2020 to January 2022, 88 HIV infected individuals were found in Pujiang County, of which 74 were transmitted through heterosexual transmission, of which 31 were infected through non-marital non-commercial heterosexual contact. Preliminary case studies have found that three female cases have engaged in unprotected non-marital non-commercial heterosexual contact with one male case. Among the 4 infected individuals, 2 of their spouses tested positive for HIV antibodies. Molecular transmission network monitoring was carried out on 65 newly diagnosed cases of heterosexual transmission with acquired sequences, forming 9 transmission clusters. The largest cluster contained 10 cases. A total of 11 HIV-infected individuals were involved in this HIV cluster epidemic. They were 3 males and 8 females, all over 50 years old and were farmers or rural housewives. They were traced to 7 sexual partners (6 negatives of HIV, 1 undetected). Among the 18 respondents' sexual social network relationships, there were 6 couples, 8 permanent partners, and 3 temporary partners. Among 11 HIV infected individuals, there were 9 cases of non-marital non-commercial heterosexual transmission and 2 cases of intramarital transmission. The epidemiological association between 7 non-married non-commercial heterosexual partners and case 2 (56-year-old male farmer), 3 cases confirmed by epidemiological investigation and molecular transmission cluster results, 3 cases confirmed by molecular transmission cluster and epidemiological investigation results, and 1 case confirmed by epidemiological investigation results.

The transmission mode of this cluster epidemic was to spread HIV through heterosexual sex with a male case as the core, then cause the transmission within marriage and between fixed sexual partners. The combination of epidemiological investigation and molecular transmission network traceability survey supports the conclusion of this study.

HIV/AIDS; Transmission relationship; Molecular transmission network; Cluster epidemic