The U.S. now has 1,024 confirmed measles cases, according to the Centers for Disease Control and Prevention.

Cases have been confirmed in 30 states, and 11 states have active outbreaks, including Texas, New Mexico, Oklahoma, Kansas, Indiana, Michigan, Montana, North Dakota, Ohio, Pennsylvania and Tennessee.

Texas still accounts for the most cases, with over 700 cases confirmed in the state this year, according to Texas Health and Human Services.

The CDC says there have been 128 hospitalizations due to measles this year, already more than the total from all of last year.

There have been three confirmed deaths from the measles in the U.S. this year.

The rising number of measles cases is causing concern as millions of people across the country get ready to travel this summer.

More than 45 million people are projected to travel during the Memorial Day holiday weekend, according to AAA, and that includes 3.6 million flyers.

RELATED STORY | Texas measles outbreak adds two new cases near Dallas-Ft. Worth

"One thing about infectious diseases, they don't respect borders," former CDC acting director Dr. Richard Besser said. "So, measles will travel."

The CDC says the virus can live in the air for two hours.

The agency says vaccination against the virus is the best protection. Two doses of the MMR vaccine are 97% effective at preventing the virus.

"If you're vaccinated against measles, you really have very little concern with the current outbreaks of measles going on," virologist and Johns Hopkins University professor Andrew Pekosz said. "But if you're unvaccinated, you're highly susceptible to infection."

The ongoing outbreaks are taking place amid increased vaccine skepticism.

The vaccine rate against measles has fallen in recent years. During the 2023-2024 school year, 92.7% of kindergarteners had the MMR vaccine, down from 95.2% during the 2019-2020 school year, according to the CDC.

"While it's a personal decision to vaccinate, that personal decision not only affects you and your child," Besser said. "It affects your neighbors. It affects others in your family, and that is what is so concerning."