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.

In Texas, there were 146 cases of measles across the state and the South Plains, with 20 patients hospitalized. The best way to prevent getting sick is to get two doses of a measles vaccine.

The number of confirmed measles cases in western Texas grew to 146, and it is possibly spreading to the central part of the state and neighboring New Mexico, health officials said Friday.