Transmission-route–specific trends in communicable diseases in Taiwan: an interrupted time-series analysis

Abstract

The COVID-19 pandemic substantially altered patterns of communicable disease (CD) transmission through implementation of non-pharmaceutical interventions and changes in healthcare utilization. However, long-term trends remain insufficiently characterized. We conducted an ecological time-series study using national surveillance data of notifiable CD in Taiwan from January 2017 to December 2023. Diseases were categorized into transmission-route groups, and temporal trends were assessed using segmented interrupted time-series models with autoregressive integrated moving average error structures to estimate phase-specific level and slope changes. A total of 240556 cases were reported, with more than 96% locally acquired. Overall incidence declined during the pandemic phase (2020–2022) and increased in 2023, exceeding pre-pandemic levels. This increase was largely influenced by dengue-related vector-borne disease activity. Substantial heterogeneity was observed across transmission pathways: airborne and droplet diseases declined markedly with partial recovery, sexually transmitted and blood-borne diseases increased consistently, and vector-borne diseases showed an outbreak-driven increase in 2023. Interrupted time-series analysis identified significant negative level changes at the onset of the pandemic and positive slope changes in the post-pandemic phase. These findings suggest transmission-route–specific temporal patterns during pandemic and post-pandemic phases and underscore the need for adaptive surveillance and prevention strategies in the post-pandemic era.