Shifting dengue virus imports into Yunnan, China, 2017-2019: epidemic lineages sparking local outbreaks.

OBJECTIVES

This study examines the genotypic diversity and transmission patterns of dengue virus (DENV) among imported cases in Yunnan.

METHODS

A total of 351 suspected imported dengue cases were studied, with infections confirmed by DENV NS1 antigen and Pan-qPCR. Serotype typing was performed through specific qPCR. Genetic and phylogeographic analyses were conducted on 228 newly obtained and 1747 publicly available DENV E gene sequences.

RESULTS

DENV infection was confirmed in 262 specimens (74.6%, 262/351). Genotypic analysis of 228 DENV E region sequences revealed all four DENV serotypes, categorized into eight genotypes and 24 unique lineages. Notably, DENV-1 (n = 143) was primarily classified as lineage 1I_E.1 (80.4%). DENV-2 (n = 52) was assigned principally to lineages 2II_F.1.1 and 2V_A.1.2. The number of lineages increased from three in 2014 to 22 in 2019, contributing to local outbreaks, especially those linked to lineage 1I_E.1. Additionally, lineages 1I_K.1.2 and 2II_F.1.1 established ongoing transmission chains. Geographic analysis identified 60 key transmission routes. Cambodia contributed to the regional transmission of DENV-1, while Yunnan and Guangdong served as important domestic hubs.

CONCLUSIONS

The introduction of diverse DENV strains has reshaped local transmission dynamics, underscoring the critical need to control imported cases to effectively prevent outbreaks.