The ongoing measles outbreak in West Texas has doubled in size to 48 cases, mostly in children and teens, making it the state’s worst in nearly 30 years.

State health officials said Friday in a news release that those who are infected are either unvaccinated or their vaccination status is unknown. Thirteen people have been hospitalized.

The outbreak has spread from its epicenter in Gaines County, with single-digit cases in nearby Lynn, Terry and Yoakum counties. Officials in the area also expect the outbreak to continue to spread in these communities.

South Plains Public Health District Director Zach Holbrooks said earlier this week that some of the cases appear to be connected to private religious schools.

Texas Department of State Health Services data shows there were 49 cases of measles in Texas in 1996. In 2013, there were 27 cases reported after a person who traveled to Asia returned and interacted with a vaccine-hesitant community, the state reported.

Measles is a highly contagious virus that can survive in the air for up to two hours. Up to 9 out of 10 people who are susceptible will get the virus if exposed, according to the U.S. Centers for Disease Control and Prevention. Before the vaccine was introduced in 1963, the U.S. saw some 3 million to 4 million cases per year. Now, it’s usually fewer than 200 in a normal year.

The U.S. saw a rise in measles cases in 2024, including an outbreak in Chicago that sickened more than 60.

Vaccination against measles, a two-shot series, is required for most U.S. kindergarteners in order for them to enroll in public school.

Texas law allows children to get an exemption from school vaccines for reasons of conscience, including religious beliefs. The percentage of kids with exemptions has risen over the last decade from 0.76% in 2014 to 2.32% last year, according to state data.

Gaines County has one of the highest rates in Texas of school-aged children who opt out of at least one required vaccine, with nearly 14% of K-12 children in the 2023-24 school year. Health officials say that number is likely higher because it doesn’t include many children who are homeschooled and whose data would not be reported.

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