Dengue Surveillance and the Emergence of New Lineages of Dengue Virus Serotype 2 (Cosmopolitan Strain) in Ho Chi Minh City

Funders:
OUCRU Programme Scientific Committee

Principal Investigators:
Tran Thuy Vi

Research Partners: Ho Chi Minh City Centre for Disease Control (HCDC)

Study Design:

Dengue fever remains a major public health issue in Ho Chi Minh City. This study investigates the circulating dengue virus serotypes and genotypes in the city, with a focus on newly emerging lineages of Dengue Virus Serotype 2 (DENV-2), known as the Cosmopolitan strain. The results will support outbreak forecasting and strengthen prevention and control efforts.

Background

Previous research by OUCRU has confirmed the co-circulation of all four dengue virus serotypes in Vietnam, with DENV-1 and DENV-2 being the most common. However, updated information on which serotypes and genotypes are currently dominant in Ho Chi Minh City (HCMC) is limited. This knowledge gap hinders efforts to predict and control outbreaks in the city.

In 2022, HCMC experienced a large dengue outbreak, with 54,026 cases reported up to September 11th, 2022, approximately 536.7% higher than in 2021. One possible explanation for this surge is the emergence of new virus lineages. Supporting this, a separate study by OUCRU (under peer review at EiD) identified two emerging DENV-2 Cosmopolitan lineages circulating in the city. Pilot genotyping data suggest these lineages may have been imported from outside Vietnam.

Objectives

To describe the current dengue virus serotypes and genotypes circulating in HCMC.
To investigate the emergence of newly detected DENV-2 Cosmopolitan lineages in HCMC, including how and when they were imported.
To generate virology data to support outbreak prediction and control, particularly the dengue forecasting tools being developed by HCDC and OUCRU.

Capacity Building

OUCRU plans to support HCDC in developing the Standard Operating Procedures (SOP) and deliver training in RT-PCR serotyping and next-generation whole genome sequencing techniques.

This collaborative effort strengthens HCDC’s molecular surveillance capacity and supports national dengue control programmes.

Study Design

This study will analyse dengue virus samples to identify serotypes, measure viral loads, and investigate the genetic diversity and spread of DENV-2 using molecular and phylogenetic methods.

Study site: Hospital for Tropical Diseases (HTD), Ho Chi Minh City

Samples: 300 patient samples from 2018 (general ward + ICU)

Method:

Viral RNA will be extracted and tested by qRT-PCR for serotype and viremia. High-viremia DENV-2 samples will undergo whole genome sequencing; others will have envelope gene sequencing.

Genetic data will be combined with regional sequences from GenBank. Phylogenetic analysis will be conducted using maximum likelihood and Bayesian MCMC approaches.

Status: The research is active and ongoing; laboratory analysis completed; data interpretation and manuscript preparation are in progress.