Overall and serotype-specific dengue virus transmission intensity in Mexico, 2016-2023: A modelling study of...

Mexico, and the Americas region more widely, have experienced increased dengue incidence in recent years, and there are concerns that the changing climate may enhance dengue virus (DENV) transmission in the future. Whilst previous studies have characterised spatial heterogeneities in the long-term average risk of DENV infection in Mexico, the extent to which DENV transmission changes year-to-year has not been investigated. Furthermore, the extent to which DENV's four serotypes (DENV-1, DENV-2, DENV-3 and DENV-4) may differ in their transmissibility remains poorly characterised, both in Mexico and globally.

In this study, we characterised the spatial and temporal variations in DENV transmission intensity, as defined by the force of infection, across 27 states in Mexico. We analysed annual dengue case data reported to the National Epidemiological Surveillance System (SINAVE) in Mexico between 2016 and 2023, which comprised 833,629 probable or confirmed cases, 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 showing a low transmission intensity throughout the study period. We found evidence of increasing DENV-3 transmission intensity across some states in recent years, coinciding with large outbreaks. The extent to which the serotype-specific transmission intensity estimates generated in this study are affected by potential heterogeneities in case reporting across states and through time remains to be validated in future studies.

This work quantifies serotype-specific differences in DENV 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 DENV transmission. The methods developed in this study contribute to the development of a better understanding of the past and current burden of dengue infection, which can help to refine assessments of the potential impact of existing and new interventions in future analyses.