Measles cases reach 1,046 in US as infections confirmed in 30 states: CDC

Measles cases have reached 1,046 as the virus continues spreading across the United States, according to data updated Friday from the Centers for Disease Control and Prevention (CDC).

Cases have been confirmed in 30 states including Alaska, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Missouri, Montana, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Texas, Vermont, Virginia and Washington.

Infectious disease experts have previously said the U.S. is likely on track to surpass the 2019 total of 1,274 cases, which were confirmed over the course of a year. This year's total also marks the second highest case count in 25 years, CDC data shows.

The CDC says 12% of measles patients in the U.S. this year have been hospitalized, the majority of whom are under age 19.

About 96% of measles cases are among those who are unvaccinated or whose vaccination status is unknown, according to CDC data.

Meanwhile, 1% of cases are among those who have received just one dose of the measles, mumps, rubella (MMR) vaccine and 2% of cases are among those who received the recommended two doses, according to the CDC.

At least three deaths have been confirmed this year, two among children and one among an adult, all of whom were unvaccinated.

It comes as an unvaccinated traveler with measles may have exposed people at Denver International Airport and a nearby hotel, health officials said on Thursday.

The patient was in the international terminal on Tuesday, May 13, and then took a shuttle to stay at the nearby Quality Inn and Suites that night. The next day, the patient took a shuttle back to the airport and boarded a domestic flight.

The Colorado Department of Public Health and Environment and the Denver Department of Public Health and Environment said anybody who may have been exposed on either flight will be directly notified by health officials.

Similarly, a resident of King County in Washington state traveled through Seattle-Tacoma International Airport and a medical center while infectious, Public Health – Seattle & King County said on Tuesday. The individual was likely exposed to measles while recently traveling internationally.

Additionally, the New Jersey Department of Health sent out an alert that a non-resident with measles attended the Shakira concert at MetLife stadium last week, potentially exposing people.

Although the concert occurred on May 16, officials warned that people may develop symptoms as late as June 6. So far, no associated cases have been identified.

The CDC currently recommends that people receive two doses of the MMR vaccine, the first at ages 12 to 15 months and the second between 4 and 6 years old. One dose is 93% effective, and two doses are 97% effective against measles, the CDC says.

Measles was declared eliminated from the U.S. in 2000 due to a highly effective vaccination program, according to the CDC. But vaccination rates have been lagging in recent years.

"I think the overall and overarching worry we have is that, as vaccination rates decline, we're starting to now see very contagious diseases such as measles come back and, generally, you need a 95% immunity wall of the population to stop an outbreak," Dr. Scott Roberts, an assistant professor at the Yale School of Medicine and medical director of infection prevention at New Haven Hospital, told ABC News.

"There are now many areas of the U.S. where we don't hit that 95% and it's much lower than that, and I think we're seeing the consequences," he continued.

Roberts say he's worried about misinformation that has arisen around the MMR vaccine such as a link between the vaccine and autism, which has been debunked by several high-quality studies.

"I worry that we are seeing this misinformation and parents are reading these things on the Internet, which is not based in truth," he said. "What we try to do as health care providers and public health professionals is really just to give the right information out there that the measles vaccine is safe. It is effective and measles itself is not a run-of-the-mill cold; it can lead to these really devastating consequences if somebody's vulnerable and gets infected."

Dr. Karen Tachi Udoh is an internal medicine resident at Johns Hopkins Hospital and a member of the ABC News Medical Unit.