This episode discusses four MMWR reports. Measles is a highly contagious vaccine-preventable disease. It can cause serious complications, particularly in young children. About 1 of every 5 people with measles have to be hospitalized. Thanks to a strong childhood vaccination program, measles stopped being constantly present in the U.S. in 2000. As the number of unvaccinated children increases, however, measles outbreaks are becoming more common. In the first report, the Cook County Department of Public Health in Illinois launched an investigation after five measles cases were reported in the fall of 2023.