A historic measles outbreak in West Texas is just short of 200 cases, Texas state health officials said Friday, while the number of cases in neighboring New Mexico 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.

Texas health officials identified 39 new infections of the highly contagious disease, bringing the total count in the West Texas outbreak to 198 people since it began in late January. Twenty-three people have been hospitalized so far.

Last week, a school-age child died of measles in Texas, the nation’s first measles death in a decade. The U.S. Centers for Disease Control and Prevention announced this week that they were sending a team to Texas to help local public health officials respond to the outbreak.

New Mexico health officials had been reporting for weeks a steady number of cases in Lea County which borders the epicenter of Texas’ outbreak. But on Friday, state health officials provided The Associated Press a week-by-week count that shows cases have steadily increased from 14 cases in the week of Feb. 9 to 30 this week.

A spokesman for the health department said more cases are expected and that many of the cases reported Friday weren’t identified until after people’s illnesses had run their course. The department has said it hasn’t been able to prove a clear connection to the Texas outbreak, though on Feb. 14, it said a link is “suspected.”

On Thursday, New Mexico health officials confirmed an unvaccinated adult who died without seeking medical care tested positive for measles. The state medical investigator has not announced the official cause of death, but the state health department said Friday it is “measles-related.”

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.

The rise in measles cases has been a major test for U.S. Health and Human Services Secretary Robert F. Kennedy Jr., an anti-vaccine activist who has questioned the safety of childhood vaccines. Recently, he has stopped short of recommending people get the vaccine, and has promoted unproven treatments for the virus, like cod liver oil.

Kennedy dismissed the Texas outbreak as “not unusual,” though most local doctors in the West Texas region told The Associated Press that they have never seen a case of measles in their careers until this outbreak.

The measles, mumps and rubella vaccine is safe and highly effective at preventing infection and severe cases. The first shot is recommended for children ages 12 to 15 months, and the second for ages 4 to 6 years.

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.

Many of Gaines County’s cases are in the county’s “close-knit, undervaccinated” Mennonite community, a diverse group that has historically had lower vaccination rates and whose members can be distrusting of government mandates and intervention.

Measles is a respiratory 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 CDC. Owing to the success of the vaccine, the U.S. considered measles eliminated in 2000.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.