# A Large Dengue Outbreak in Taiwan, 2023: Driven by Imported Cases, Serotype Cocirculation, and Climate Variability

## TL;DR

In 2023, Taiwan experienced a large dengue outbreak driven by imported cases, multiple virus types, and changing climate conditions.

## Contribution

The study identifies the complex interplay of imported cases, serotype cocirculation, and climate factors in a non-endemic region.

## Key findings

- Dengue cases in 2023 were primarily in Tainan and Kaohsiung, with cocirculating DENV-1 and DENV-2 strains.
- Genomic analysis showed 2023 strains were genetically linked to Southeast Asian isolates.
- Transmission drivers varied between cities, with climate and vector indices playing key roles.

## Abstract

Taiwan, a region traditionally considered non-endemic for dengue, experienced an unexpected and large-scale outbreak in 2023. We investigated the multifactorial drivers of this outbreak, including cross-border viral importation, serotype cocirculation, vector ecology, and climate variability.

We analyzed national dengue surveillance data (2013–2023), meteorological records, and Breteau Index (BI) values, alongside molecular serotyping and whole-genome sequencing of clinical isolates. Time-lagged Poisson regression was used to identify predictors of indigenous dengue transmission in Kaohsiung and Tainan. Full-genome comparisons were conducted between 2023 strains and historical epidemic isolates.

A total of 26 706 laboratory-confirmed cases were reported, primarily in Tainan (80.7%) and Kaohsiung (11.9%). Real-time RT-PCR identified cocirculating DENV-1 and DENV-2 strains. Phylogenetic analysis confirmed the 2023 DENV-1 and DENV-2 strains were genetically linked to contemporary strains from Southeast Asian countries. Whole-genome sequencing identified several nonsynonymous mutations in the NS2A, NS3, and NS5 regions when compared with historical outbreak isolates. Time-lagged regression showed that imported cases, precipitation, and the BI were associated with incidence in univariate models. In Kaohsiung, the best-fitting multivariable model included the BI, but temperature and precipitation were the independent predictors. In Tainan, precipitation and, at longer lags, imported cases were more influential, while the BI lost significance after adjustment.

The 2023 dengue outbreak in Taiwan was driven by a complex interplay between viral introductions, climatic conditions, and vector dynamics. The differing transmission drivers observed between cities highlight the need for region-specific vector surveillance, climate-informed early warning systems, and sustained genomic monitoring to prevent future re-emergence of dengue in this non-endemic setting.

An unexpected large dengue outbreak occurred in Taiwan in 2023, driven by imported cases, serotype cocirculation, climate variation, and vector density. Region-specific time-lagged models identified differing transmission drivers between Kaohsiung and Tainan, highlighting the need for targeted control strategies.

Graphical AbstractThis graphical abstract is also available at Tidbit: https://tidbitapp.io/tidbits/a-large-dengue-outbreak-in-taiwan-2023-driven-by-imported-cases-serotype-co-circulation-and-climate-variability-cf1fdbc5-bd6f-4791-8066-5ca1117fcab7

This graphical abstract is also available at Tidbit: https://tidbitapp.io/tidbits/a-large-dengue-outbreak-in-taiwan-2023-driven-by-imported-cases-serotype-co-circulation-and-climate-variability-cf1fdbc5-bd6f-4791-8066-5ca1117fcab7