Spatiotemporal Dynamics of the 2025-2026 Measles Outbreak in Mexico: Jalisco as the Emerging Epicenter and the Impact of Intensive Immunization Efforts.

Measles represents a critical public health challenge due to its high transmissibility and the resurgence of outbreaks of the disease, linked to gaps in vaccination coverage. In this study, we analyze the epidemiological dynamics of the outbreak that began in Mexico in 2025 and focus on Jalisco as the epicenter during the first quarter of 2026. A descriptive, retrospective, ecological time-series analysis was conducted using official epidemiological surveillance data, correlating incidence with immunization strategies. The results reveal that 6681 cases were recorded in Jalisco, with the highest prevalence among adults aged 20 to 49 years (41.96%), which highlights the accumulated gaps in immunity coverage. The public health response, comprising the administration of three million doses, focusing on zero-dose children and vaccination blockades, contributed to a notable decrease in infections by epidemiological week 17 of 2026. It was concluded that the outbreak was controlled through intensive and coordinated intervention. However, the proximity of the 2026 International Federation of Association Football (FIFA) World Cup requires vaccination coverage to be maintained at over 95%, in addition to vigilance, to mitigate the risk of viral reintroduction and to safeguard global health security.