Three serotypes of dengue virus circulated in hospitalized adult patients in an endemic metropolitan city of Northern Vietnam

Dengue virus (DENV) is a positive-sense single-stranded RNA virus belonging to the genus Flavivirus within the Flaviviridae family. Four serotypes, DENV 1-4, are distributed globally. Hanoi metropolitan city is an endemic hotspot for DENV transmission in Vietnam. The largest outbreak occurred in 2017, with more than 36 000 cases and 7 deaths reported, causing by all four serotypes with the predominance of DENV1, following by DENV2. During the following dengue season, we collected 390 blood and serum samples from 197 hospitalized patients in a national hospital in Hanoi city, Northern Vietnam to identify the circulating DENV serotypes responsible for the 2018-2019 outbreak.

This retrospective case-control study was a continuation of previously published work that was conducted in Bach Mai hospital, one of the largest medical healthcare facility in Vietnam. The patients were recruited among people living in Hanoi and hospitalized at the Department of Infectious Diseases, Bach Mai hospital for dengue-like symptoms. All procedures performed in this research involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Ethical approval for this research was obtained from the Ethical Committee of Bach Mai hospital No. 690/QD-BM on 15 September 2018. Both written and oral informed consents were collected before taking blood samples. The respondents participated voluntarily in the study after being explained clearly about the research. All information was handled anonymously, research data was only approached by the research team. The laboratory and sequencing results were last analyzed in December 2022.