Dengue virus (DENV) causes a growing public health burden in Mexico and the wider Americas, with rising numbers of reported cases in recent years. The principal vector, Aedes aegypti, thrives in urban settings and climatic changes are expected to influence the geographic distribution and intensity of transmission. Mexico has historically experienced higher dengue burden in coastal and tropical southern regions and lower endemic transmission in much of the northern-central high-altitude plateau.
DENV comprises four antigenically distinct serotypes (DENV-1, DENV-2, DENV-3, DENV-4). Infection generates long-term homotypic immunity and shorter-lived heterologous protection; these immunological dynamics, together with cyclical transmission patterns, contribute to inter-annual variability and irregular large outbreaks. Prior modelling efforts often assumed equal transmissibility among serotypes because serotype-specific data have been scarce.
The study analysed annual dengue case notifications reported to Mexico’s Sistema Nacional de Vigilancia Epidemiológica (SINAVE) from 2016 through 2023. The dataset comprised 833,629 probable or confirmed dengue cases aggregated across 27 Mexican states. Where available, individual records contained serotype information determined by RT-PCR or other diagnostics.
Population denominators were derived from Mexico’s intercensal survey (2015) and the 2020 census. Aggregated data and the modelling code were made available by the authors via GitHub and Zenodo. Line-list data for 2020–2023 are publicly accessible from the Mexican Ministry of Health; data for 2016–2019 were obtained from the Instituto Nacional de Acceso a la Información (INAI) and are available on request via Mexico’s transparency platform.
Researchers applied established catalytic models to estimate transmission intensity, defined as the force of infection (FOI), using the age and temporal distribution of reported cases. In addition to overall FOI, the team developed a new serotype-specific extension of catalytic models to estimate differences in transmission intensity between the four DENV serotypes.
The serotype-specific model uses observed serotype-identified cases to infer the contribution of each serotype to overall transmission. The approach quantifies spatial (state-level) and temporal (annual) variation in FOI and allows comparison of relative transmissibility across DENV-1, DENV-2, DENV-3, and DENV-4.
Estimated FOI varied substantially between states and from year to year. Higher transmission intensity estimates were concentrated in southern coastal and tropical states where dengue is commonly endemic or hyper-endemic. Lower FOI estimates were estimated for northern-central regions of Mexico, particularly areas at higher altitude where transmission is more limited.
The country experienced cyclical dynamics with seasonal peaks typically between August and November and larger inter-annual outbreaks occurring approximately every 3–4 years. The study noted that 2023 had higher transmission intensity in the south relative to prior years, consistent with reported high case counts in that year.
Serotype-specific FOI estimates indicated notable heterogeneity across serotypes and space–time:
DENV-1 and DENV-2: These serotypes were estimated to have historically circulated at relatively high intensity across many parts of Mexico during 2016–2023.
DENV-4: This serotype showed consistently low transmission intensity throughout the study period at the national scale.
DENV-3: The analysis identified an increase in DENV-3 transmission intensity in some states in recent years, coinciding with observed large outbreaks in those locations.
These serotype-specific patterns imply that population immunity profiles vary substantially by region and over time, reflecting heterogeneous exposure histories to different serotypes.
The authors explicitly note key model assumptions and limitations that affect interpretation of results:
The serotype-specific model assumes that the four serotypes do not differ in their propensity to cause symptomatic disease. This assumption remains to be validated in Mexico and globally.
The model also assumes that the subset of reported cases with serotype data is representative of the serotypes circulating in the population. If diagnostic testing or sampling is biased, serotype-specific FOI estimates may be affected.
Heterogeneities in case reporting across states and through time—variability in health-seeking behaviour, diagnostic capacity (including RT-PCR coverage), and surveillance sensitivity—could influence FOI estimates. The extent of such effects was not fully resolved in this study and requires validation in future work.
The analysis relies on routinely collected surveillance data; therefore, underreporting and differences in reporting completeness are inherent limitations.
The study demonstrates how combining routine case-notification data with catalytic and serotype-specific models can quantify both overall and serotype-level transmission intensity. The authors emphasise the value of extensive RT-PCR testing and deployment of rapid diagnostics capable of identifying infecting serotypes to strengthen surveillance. Improved serotype-resolved surveillance would support better understanding of serotype contributions to transmission, more accurate assessments of population immunity, and more informed planning for interventions such as vector control and vaccine deployment.
The heterogeneity documented implies that control strategies and impact assessments may need to be tailored subnationally, taking into account differing serotype circulation and changing FOI over time.
Aggregated data and the code required to run the models are available via the project GitHub repository and on Zenodo. Line-list dengue case data for 2020–2023 are publicly available from the Mexican Ministry of Health; data for 2016–2019 were obtained through INAI and can be requested via Mexico’s National Transparency Platform.
Funding acknowledgements included support for the MRC Centre for Global Infectious Disease Analysis and Wellcome Trust funding for one author. The funders did not influence study design, data collection, analysis, manuscript preparation, or publication decisions. The authors declared no competing interests.
Using 833,629 reported dengue cases from 2016–2023, this modelling study quantified substantial spatial, temporal, and serotype-specific heterogeneity in DENV transmission intensity across Mexico. The findings highlight higher historical circulation of DENV-1 and DENV-2, low transmission of DENV-4, and increasing DENV-3 intensity in some states in recent years. The authors stress that validation of model assumptions and the potential influence of reporting heterogeneities are priorities for future studies. Enhanced serotype-resolved diagnostics and surveillance are recommended to improve estimates of serotype-specific transmission and to inform targeted public health responses.