Abstract
OBJECTIVES: The bidirectional increase of visitors between Vietnam and Japan has raised concerns about the spread of CRF01_AE; however, the epidemiological characteristics of CRF01_AE in Vietnam and its relationship with Japan remain unclear. We compared the CRF01_AE gene sequences from Vietnam and Japan to understand their epidemiolocal relationships. DESIGN: A molecular-epidemiological observational study. METHODS: We analyzed 753 protease--reverse transcriptase sequences from CRF01_AE-infected individuals in northern Vietnam and 500 CRF01_AE sequences from the Japanese Drug Resistance HIV-1 Surveillance Network's cluster database. We inferred the chronological phylogeny of these sequences with HIV-1 subtype references and identified statistically significant Vietnam-related clusters (VRCs). Individuals' sex, infection risk, age, collection year, collection site, and nationality were analyzed in relation to clustering and bilateral epidemiological relationships. RESULTS: A total of 33 VRCs and 41 Vietnam-related pairs were identified. Of these, eight were linked to known Japanese domestic transmission clusters (dTCs). Two VRCs included Vietnamese individuals diagnosed in Japan. One Japanese dTC linked to Vietnam included numerous Philippine nationals who were diagnosed in Japan. Regression analysis revealed that VRCs with a higher proportion of young people had a higher number of MSM (adjR 2 = 0.422, P < 0.001). Although VRCs involved different risk groups in northern Vietnam, a strong association was observed between bilateral epidemic links and MSM (adjOR = 8.718, P < 0.001). CONCLUSION: CRF01_AE in northern Vietnam has spread through many different at-risk populations. Some MSM groups were associated with the epidemiological relationship between northern Vietnam and Japan.