Cases of measles have been reported in 12 states since the beginning of 2025 and jumped by 35% over the past week, according to the Centers for Disease Control and Prevention.
Health officials say West Texas has almost 200 measles cases and New Mexico's case number has tripled to 30.
Most of the cases across both states are in people younger than 18 and people who are unvaccinated or have an unknown vaccination status.
Last week, a school-age child died of measles in Texas, the nation's first measles death in a decade. The CDC announced this week that it was sending a team to Texas to help local public health officials respond to the outbreak.
Measles typically kills 1 to 3 people per 1,000 cases, said Dr. Tina Tan, an infectious disease expert at Northwestern University in Chicago.
The CDC said Friday it has also confirmed measles cases in Alaska, California, Florida, Georgia, Kentucky, New Jersey, New York City, Pennsylvania, Rhode Island, and Washington. But the Texas and New Mexico outbreaks make up for most of the nation's case count.
On Thursday, state health officials announced an adult who was infected with measles has died in New Mexico, though the virus has not been confirmed as the cause.
The person who died was unvaccinated and did not seek medical care, a state health department spokesperson said in a statement.
The person was from Lea County, just across the state line from the West Texas region where the child died last week.
Childhood vaccination rates across the country have declined as an increasing number of parents seek exemptions from public school requirements for personal or religious reasons. In Gaines County, Texas, which has the majority of cases, the kindergarten measles vaccination rate is 82% — far below the 95% needed to prevent outbreaks.
Information from The Associated Press was used in this report.
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