Epidemiological characteristics and importation patterns of imported dengue fever in southwest border regions of China.

Dengue fever is a global public health issue of international concern. The southwestern border regions of China (Yunnan Province) are an important gateway for imported dengue fever cases in China. This study aims to investigate the importation patterns of imported dengue cases in Yunnan Province to support global dengue prevention efforts. This study examined imported dengue cases in Southwestern border regions of China, comparing actual and predicted cases via a counterfactual model under COVID-19 measures. Social network analysis was used to identify the importation pattern. From 2012 to 2023, 6,205 imported dengue cases were reported, making up 20.2%. The main sources were Southeast Asian countries: Myanmar (86.6%), Laos (5.8%), and Cambodia (4.9%). During the COVID-19 pandemic, imported cases dropped dramatically when borders closed, with predicted case counts being approximately 16.2-fold, 315.3-fold, and 12.3-fold higher than observed counts from 2020 to 2022, respectively, reflecting the sharp reduction in cross-border mobility during this period. In 2023, observed cases exceeded predictions by 45.0%. The cumulative social network identified three transmission communities centered around Kunming and Xishuangbanna in China, and Myanmar. The community centered in Myanmar had a bridging closeness centrality of 3.67, mainly connecting to Chinese border cities like Dehong (3.7) and Lincang (3.7). The Xishuangbanna community had a centrality of 3.4, primarily linking to Laos (3.4). The Kunming community had the highest centrality at 4.4, connecting mainly to non-border countries including Thailand (4.0), Cambodia (4.3) and Malaysia (2.8). Imported dengue cases in China's southwest border regions exhibit a dual-center pattern: land-border cases cluster in cities adjacent to Myanmar and Laos, while air-border cases concentrate in Kunming. Future efforts should enhance port monitoring and cross-border cooperation.