# Molecular Transmission Dynamics of HIV-1 in Migrant Populations: Transmission Clusters and Demographic Diversity in Hangzhou, a Key Migration Hub in Eastern China

## TL;DR

This study explores how HIV spreads among migrant populations in Hangzhou, China, using genetic data to identify transmission clusters and demographic patterns.

## Contribution

The study provides new insights into the role of migrant populations in HIV transmission and identifies population-specific factors influencing molecular transmission networks.

## Key findings

- Migrant populations form multiple large HIV transmission clusters in Hangzhou.
- PMP and NMP have higher inclusion rates in molecular transmission networks compared to TMP.
- Factors like current residence and STD history are associated with network inclusion for migrants.

## Abstract

Objective: Population mobility complicates the prevention and control of HIV. To address these challenges, this study explored the molecular epidemiology of HIV among migrant populations in Hangzhou. Methods: People newly diagnosed with HIV/AIDS from 2020 to 2023 were divided into permanent migrant population (PMP), temporary migrant population (TMP), and non-migrant population (NMP). HIV-1 pol gene sequencing was performed to calculate genetic distance. Sample pairs with genetic distances ≤0.005 were used to construct the molecular transmission network. Results: PMP comprised people living with HIV in Hangzhou, characterized by younger age, higher education, and predominantly homosexual transmission. This population forms multiple large molecular clusters together with NMP. TMP accounted for the highest proportion of females and people infected through heterosexual contact, but the education level was the lowest. NMP had the fewest people living with HIV. The main subtypes identified were CRF01_AE, CRF07_BC, CRF08_BC and CRF55_01B. Drug resistance prevalence did not differ significantly among the populations. The molecular transmission network included 833 cases forming 275 clusters, with an overall sample inclusion rate of 23.04%. PMP, TMP and NMP inclusion rates were 27.10%, 19.03% and 21.4%, respectively. All molecular clusters involved migrant populations. Factors associated with inclusion in the network for migrants included current residence, household registration, STD history, sample source, and stage at diagnosis. Conclusions: Migrant populations play a major role in ongoing HIV transmission. Prevention and control measures should be strengthened according to population-specific characteristics. Molecular transmission networks are useful tools for assisting precise control.