The West Texas measles outbreak, the largest the United States has seen in more than two decades, is officially over, according to the Texas Department of State Health Services (DSHS) on Aug. 18.
The department stated that 42 days had passed with no new reported cases. Health officials use this benchmark because measles has a 21-day maximum incubation period—the longest it can take between exposure to the virus and the onset of symptoms, so two full incubation cycles without new cases indicates that the outbreak has been contained.
