# Emergence of Two New Lineages of the Cosmopolitan Dengue Virus Serotype 2 in Yunnan, China, 2024

## TL;DR

This study identifies two new lineages of dengue virus serotype 2 in Yunnan, China, tracing them to Thailand and Cambodia, highlighting the need for cross-border prevention.

## Contribution

The discovery of two new cosmopolitan DENV-2 lineages in Yunnan, China, with distinct geographic origins.

## Key findings

- Two new lineages of DENV-2 were identified in Yunnan, likely originating from Thailand and Cambodia.
- The Xishuangbanna region showed more diverse and complex DENV-2 genotypes compared to other regions.
- Phylogenetic analysis revealed distinct genetic clustering of the two lineages.

## Abstract

Dengue fever has become a significant epidemic in South and Southeast Asia. Recently, Yunnan Province in southwestern China, which borders these regions, has also experienced a significant outbreak. This study aims to investigate the genetic diversity of the dengue virus (DENV) and identify potential sources of transmission in Xishuangbanna, Yunnan Province in 2024.

In 2024, we investigated 321 suspected cases of dengue fever in Yunnan Province. We screened dengue fever patients using a combination of DENV NS1 antigen and Pan-qPCR methods, and performed serotype typing using specific qPCR. We also performed phylogenetic and molecular clock analyses to understand the genotypes and transmission sources.

DENV infection was detected in 101 of 321 specimens. Serotype and genotype analysis were performed on 88 of the 98 positive samples. The results showed that 81 cases belonged to the cosmopolitan genotype and cosmopolitan_asian-pacific subtype of DENV serotype 2 (DENV-2), while only 1 case was classified as genotype I and subtype 1L of DENV serotype 1 (DENV-1). Notably, samples within the cosmopolitan_asian-pacific subtype were primarily divided into 2 distinct lineages. Further analysis of whole-genome sequences, focusing on phylogenetic history and spatiotemporal dynamics, indicated that lineage-1 likely originated in Thailand, while lineage-2 may have originated in Cambodia. In addition, we analyzed all available DENV-2 sequences from Yunnan in the GenBank database and found that DENV-2 genotypes in the Xishuangbanna region were more diverse and complex.

This study identifies 2 new lineages of cosmopolitan DENV-2 in Yunnan, originating from Thailand and Cambodia, respectively.

This study reports on 2 new cosmopolitan lineages of DENV-2 in Yunnan, China, in 2024, tracing them back to their origins in Thailand and Cambodia. It is essential to strengthen cross-border dengue fever prevention and control measures in Yunnan.