Risk and Spatial Spread of a Measles Outbreak in Texas.

In January 2025, a measles outbreak was reported in Gaines County, Texas, and subsequently spread to other counties and states. However, investigations into the geographic spread of this outbreak remain limited. We developed a measles transmission model parameterized with 2020-2024 measles-mumps-rubella (MMR) vaccination coverage and human mobility data in Texas. We conducted sensitivity analyses to evaluate how variation in model parameters affects outcomes. We compared model predictions to data from the 2025 measles outbreak and simulated scenarios for outbreak originating in different low vaccination counties. We found that an outbreak originating in Gaines County would have at least 80% probability of directly generating local outbreaks in eight neighboring counties in West Texas. The spatial spread was highly sensitive to the basic reproduction number (R0) and population-level MMR vaccination coverage. Outbreaks originating in counties with low MMR vaccination rates, such as Polk, Montague, or Limestone County, are likely to spread to large metropolitan areas such as Houston and Dallas. Measles has the potential to cause statewide outbreaks in Texas. Our modeling framework can inform county-level risk assessment and guide preemptive vaccination strategies.