Changes in dengue virus transmission in Mexico: 2016-2023

Mexico has experienced increased dengue incidence in recent years, and there are concerns that the changing climate may enhance dengue transmission in the future. Whilst previous studies have characterised spatial heterogeneities in the long-term average risk of dengue infection in Mexico, the extent to which dengue transmission changes year-to-year has not been investigated. Furthermore, the extent to which dengues four serotypes may differ in their transmissibility remains poorly characterised globally. In this study we characterised the spatial and temporal variations in dengue transmission intensity, as defined by the force of infection, across 27 states in Mexico, by analysing the annual dengue cases reported to surveillance between 2016 and 2023 using established catalytic models and a new, serotype-specific extension of these models that characterises differences in the transmission intensity of the different serotypes. We found evidence of large spatial, temporal, and serotype-specific heterogeneities in transmission intensity across Mexico. Serotype-specific force of infection estimates suggest that DENV-1 and DENV-2 have historically circulated at high levels across Mexico, with DENV-4 transmission intensity low throughout the period studied. Model estimated DENV-3 transmission intensity increased in some states in recent years, coinciding with large outbreaks. This work quantifies serotype-specific differences in dengue transmission intensity using routinely collected case-notification data and demonstrates how extensive RT-PCR-testing and new rapid diagnostic tests capable of discerning infecting serotypes can help to better understand the contributions of different serotypes to transmission.