Two doses of the measles-mumps-rubella (MMR) vaccine are 97% effective against the measles virus. (Photo Credit: Annie Rice/Reuters via CNN Newsource)

(CNN) — Three hundred and twenty-one cases have been reported in the ongoing measles outbreak in Texas, New Mexico and Oklahoma, the states said Tuesday. This is an increase of 25 cases since an update on Friday.

Texas has reported 279 outbreak-associated cases, New Mexico has reported 38 cases, and Oklahoma had previously reported four cases.

Thirty-eight patients have been hospitalized, an increase of two over last week. Ninety-five cases are in children up to age 4, and 130 are among young people ages 5 to 17. Cases have been identified in 11 Texas counties and two New Mexico counties.

In Texas, the bulk of the cases, 191, are in Gaines County, where the outbreak was first identified. In New Mexico, most cases are in Lea County, which borders Gaines County.

The Oklahoma State Department of Health said last week that it had four measles cases in people with “exposure associated with the Texas and New Mexico outbreak.”

Although most of the cases are in people who were unvaccinated or who had unknown vaccination status, six were found in people who said they have received at least one dose of the measles-mumps-rubella (MMR) vaccine: two in Texas and four in New Mexico.

Last month, Texas announced the outbreak’s first death, a school-age child who was not vaccinated and had no underlying conditions. Health officials in New Mexico are continuing to investigate the cause of death of an unvaccinated person who tested positive for measles.

Given the highly contagious nature of the disease, officials expect continued spread.

“This is going to be a large outbreak, and we are still on the side where we are increasing the number of cases. … I’m really thinking this is going to be a year long,” Katherine Wells, director of Lubbock Public Health, said at a briefing Tuesday.

“I just think, it being so rural now, multistate, it’s just going to take a lot more boots on the ground, a lot more work to get things under control. It’s not an isolated population.”

However, officials say that increased testing capacity will be helpful in containing the outbreak.

Labs have been set up in Lubbock, close to the epicenter of the outbreak. This means specimens no longer need to be sent via plane to Austin, reducing the time to get results from 72 hours to the same day.

At Tuesday’s briefing, officials noted that identifying cases, exposures and unvaccinated people was critical in curtailing a measles outbreak in Chicago last year.

“As long as we continue to have a pool of unvaccinated people, it will continue to spread. So it’s very hard to say it has peaked unless you have successfully vaccinated everyone who is unvaccinated,” said Dr. Olusimbo Ige, commissioner of the Chicago Department of Public Health.

Last year, 30,000 MMR vaccinations were given to Chicago residents during the outbreak, which kept it from crossing the 100-case mark, according to the US Centers for Disease Control and Prevention. Instead, the outbreak stopped at 64 reported cases, most of them linked to a shelter.

According to a CNN tally, there have been at least 353 cases reported in the US as of March 18. This already surpasses the total number of cases for all of last year.

In 2024, there were 285 total measles cases reported in the US, according to data from the US Centers for Disease Control and Prevention. This is only the third year since measles was eliminated in the US in 2000 that an outbreak has led to more 200 cases. The others were 2014, when there was an outbreak tied to Disneyland, and 2019, when a nearly year-long outbreak in New York came within weeks of ending elimination status in the US.

The CDC has been assisting efforts on the ground in Texas, and Dr. Philip Huang, director of Dallas County Health and Human Services, says local efforts are “dependent” on federal support.

“Our staffing to be able to do vaccination clinics and our epidemiology staff to do the investigations and contact tracing … so much of that is federally funded that we are very dependent on and very concerned about some of the potential staffing cuts that we’re seeing at the federal level, as well as some of the budget cuts,” he said Tuesday.

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