Epidemic Years Increase Hospitalization but Not Mortality Among Laboratory-Confirmed Dengue Cases in Mexico: A Nationwide Surveillance Study, 2020-2025.

Dengue is a major public health problem in Mexico, where large epidemics have occurred during recent years. Although demographic and clinical predictors of severe dengue have been widely studied, the impact of epidemic transmission periods on hospitalization and mortality remains poorly understood. This study evaluated the association between epidemic years and hospitalization and mortality among laboratory-confirmed dengue cases in Mexico. A nationwide retrospective analytical study was conducted using laboratory-confirmed dengue cases reported through the Mexican National Epidemiological Surveillance System between 2020 and 2025. Years were classified as epidemic (2023-2024) or non-epidemic (2020-2022 and 2025) according to official endemic channel analyses. Hospitalization and mortality were evaluated as primary outcomes. Multivariable logistic regression models were developed to identify factors independently associated with hospitalization and mortality. A total of 235,226 laboratory-confirmed dengue cases were included, of whom 90,661 (38.5%) were hospitalized and 1604 (0.68%) died. Overall, 170,819 cases (72.6%) occurred during epidemic years. Hospitalization was more frequent during epidemic years than during non-epidemic years (40.2% vs. 34.1%; crude OR 1.30, 95% CI 1.27-1.32; p < 0.001), whereas mortality did not differ significantly (0.68% vs. 0.69%; crude OR 0.99, 95% CI 0.89-1.11; p = 0.919). In multivariable analysis, epidemic-year status remained independently associated with hospitalization (aOR 1.26, 95% CI 1.24-1.29; p < 0.001) but not with mortality (aOR 1.00, 95% CI 0.90-1.12; p = 0.946). Chronic kidney disease showed the strongest independent association with both hospitalization (aOR 5.36, 95% CI 4.33-6.65) and mortality (aOR 6.98, 95% CI 5.23-9.32). Advanced age and other underlying comorbidities were also independently associated with adverse outcomes. Epidemic years were associated with increased hospitalization among laboratory-confirmed dengue cases in Mexico but were not associated with increased mortality. Mortality was more strongly associated with age and underlying comorbidities, particularly chronic kidney disease. These findings highlight the importance of strengthening hospital preparedness during epidemic periods while prioritizing clinical monitoring of high-risk patients.