# An individual with multiple high-risk links uncovered: an epidemiological investigation based on molecular network analysis

## TL;DR

A study in China used molecular network analysis and epidemiological investigations to identify an HIV transmission cluster involving young students and MSM, revealing a high-risk individual who was not initially in the cluster.

## Contribution

The study demonstrates how combining molecular network analysis with detailed epidemiological investigations can uncover hidden high-risk individuals in HIV transmission clusters.

## Key findings

- Molecular network analysis identified a key cluster involving young students and nonstudent MSM.
- A high-risk individual (H) was identified through app data and sexual partner tracing, linking to multiple HIV-positive individuals.
- Combining molecular and epidemiological data helped detect a potential transmission hub and prevent further spread.

## Abstract

In December 2023, the local HIV confirmatory laboratory in a Southwestern city of China conducted molecular network analysis on newly reported cases of young students and nonstudent men who have sex with men (MSM) from 2018 to 2023 and identified a key molecular cluster. The aim of the study is to analyze the transmission network characteristics and elucidate the potential transmission dynamics within this cluster, and prevent further spread of the disease.

A cluster was designated as a key molecular cluster based on node characteristics, internal network density, and whether young students were involved. For the key cluster, a face-to-face epidemiological investigation was conducted, and detailed information on sociodemographic characteristics, histories of high-risk sexual behavior and sexual partners was collected. For those individuals identified through sexual partner tracing, HIV nucleic acid extraction, HIV-1 pol gene amplification, and sequencing were performed. Molecular network and ML phylogenetic tree analyses were conducted to verify whether they belong to the same molecular cluster.

All 20 individuals in the key molecular cluster were male, with 9 being young students and 11 being nonstudent MSM The investigations revealed that three young students (A, B, C) provided the geosocial networking app (Blued) account information of the same high-risk sexual partner (H, was not included in the aforementioned molecular cluster), who actively solicited unprotected anal sex with these three individuals. H was contacted through Blued by local MSM organizations, and tested HIV-positive. After sexual partner tracing of H, he provided information on one high-risk sexual partner (D). Cross-referencing H’s Blued data with local AIDS sexual partner tracing databases linked him to two young students diagnosed with HIV (E, F). Laboratory molecular network analysis confirmed that H belonged to the same molecular cluster as the aforementioned six people living with HIV (PLWH).

By combining molecular transmission network analysis with epidemiological investigations, one individual with multiple high-risk sexual links who was initially not included in the molecular cluster was promptly detected, potentially preventing further transmission by creating awareness of HIV status and provision of HIV treatment services. It is necessary to improve the molecular network monitoring and conduct high-quality epidemiological investigation on the identified key molecular clusters as soon as possible to find persons who would benefit from HIV treatment and prevention services.