Clinical Report: Initial Molecular Detection of Tembusu Virus in Mosquitoes from Vietnam

Overview

This study provides the first mosquito-based molecular evidence of a Tembusu virus (TMUV)–related virus in Vietnam. A partial TMUV draft genome was recovered from field-caught Culex tritaeniorhynchus mosquitoes collected in rural southern Vietnam.

Background

TMUV is an emerging flavivirus primarily associated with disease in ducks, although other avian hosts may also be affected. Mosquito transmission is considered likely, and the virus has previously been detected in mosquitoes and birds elsewhere in Asia. TMUV was previously identified in domestic ducks in Vietnam, but molecular evidence from field-caught mosquitoes had been lacking.

Data Highlights

• Mosquitoes collected: 18,091

• Female mosquitoes screened: 10,658

• Mosquito species represented: 4

• Mosquito pools tested: 586

• Sampling sites: 12

• Geographic regions: 4

• TMUV-positive pool: 1

• Mosquitoes in the positive pool: 25

• Recovered genome length: 6,764 bases

• Complete-genome coverage: 61.5%

Key Findings

• A TMUV draft genome was recovered from a Cx tritaeniorhynchus pool collected at a rural site in southern Vietnam.

• The sequence clustered within a regional TMUV clade containing strains from China, Thailand, Taiwan, and Vietnam.

• The clade predominantly comprised poultry-associated sequences but also included mosquito-derived sequences.

• The Vietnamese sequence had 98.44% nucleotide similarity to 2 Chinese sequences derived from mosquito and chicken hosts.

• Nine pools produced pan-flavivirus RT-PCR bands, but Sanger sequencing did not permit definitive viral identification. One pool with a TMUV-like signal subsequently yielded a draft genome through viral metagenomic sequencing.

• No alphavirus-positive bands or other arbovirus sequences relevant to the study objective were identified.

Clinical Implications

The findings support mosquito surveillance as a means of identifying viral diversity not captured through investigations of poultry outbreaks alone. However, detection of viral RNA does not confirm infectious virus or establish that Cx tritaeniorhynchus can transmit TMUV. The study did not evaluate human infection, clinical disease, treatment, or public health interventions.

Conclusion

The recovery of a TMUV-related draft genome from field-caught mosquitoes provides initial molecular evidence of mosquito-associated TMUV in Vietnam. Longitudinal mosquito and avian-host surveillance, TMUV-specific molecular assays, virus isolation, and complete-genome sequencing are needed to define its prevalence, distribution, genetic diversity, and transmission ecology.

Related Resources & Content

1. First Mosquito-Based Molecular Evidence of Tembusu Virus in Vietnam — Loc DH, Sulesco T, Tóth GE, et al. International Journal of Infectious Diseases. 2026;170:108927. doi:10.1016/j.ijid.2026.108927.

2. Isolation and Characteristics of Tembusu Virus From Ducks in Southern Vietnam — Quoc CN, Thai BP, Anh VD, et al. European Poultry Science. 2024;88:1–11. doi:10.1399/eps.2024.401.

3. Duck Tembusu Virus in North Vietnam: Epidemiological and Genetic Analysis Reveals Novel Virus Strains — Dong HV, Tran GTH, Vu TTT, et al. Frontiers in Veterinary Science. 2024;11:1366904. doi:10.3389/fvets.2024.1366904.

4. Identification of the Tembusu Virus in Mosquitoes in Northern Thailand — Hamel R, Vargas REM, Rajonhson DM, et al. Viruses. 2023;15:1447. doi:10.3390/v15071447.