The number of people with measles in Texas increased to 146 in an outbreak that led this week to the death of an unvaccinated school-aged child, health officials said Friday.

The number of cases — Texas’ largest in nearly 30 years — increased by 22 since Tuesday. The Texas Department of State Health Services said cases span over nine counties in Texas, including almost 100 in Gaines County, and 20 patients have been hospitalized.

The child who died Tuesday night in the outbreak is the first U.S. death from the highly contagious but preventable respiratory disease since 2015, the U.S. Centers for Disease Control and Prevention said. The child was treated at Covenant Children’s Hospital in Lubbock, though the facility said the patient didn’t live in Lubbock County.

Robert F. Kennedy Jr., the nation’s top health official and a vaccine critic, said Wednesday that the U.S. Department of the Health and Human Services was watching cases but dismissed the outbreak as “not unusual.”