Risk and Spatial Spread of a Measles Outbreak in Texas

Background: In January 2025, a measles outbreak was reported in Gaines County, Texas, and spread to other counties and states. However, investigations on the risk of the geographical spread of such an outbreak are limited. Methods: In this study, we developed a measles transmission model parameterized with 2020-2024 measles-mumps-rubella (MMR) vaccination coverage and human mobility data in Texas. We compared model predictions to data from the 2025 measles outbreak in West Texas and simulated counterfactual outbreak scenarios in Texas under different vaccine uptake and originating counties. Results: We showed that a measles outbreak originating in Gaines County would have at least an 80% probability of directly generating local outbreaks in six neighboring counties (Terry, Lubbock, Yoakum, Andrews, Ector, and Midland County) in West Texas. When considering second-generation outbreaks, seven additional counties - El Paso, Bexar, Tarrant, Dallas, Harris, Dawson, and Hockley County - had at least a 60% probability of experiencing a local outbreak. Moreover, we showed that an outbreak originating in a low MMR-vaccine county, such as Polk, Montague, and Limestone County, has at least an 80% probability of causing large outbreaks in metropolitan areas such as Houston and Dallas. Moreover, we showed that a statewide increase in vaccine coverage is necessary to prevent large-scale measles outbreaks in Texas. Conclusions: Measles has the potential risk of causing statewide outbreaks in Texas. Our study provides a modeling framework that can be used to inform county-level risk and spread of a measles outbreak and evaluate pre-emptive vaccination strategies.