CDC Issues Health Alert Over Growing Cases of Measles in the U.S. and Abroad

Health officials recommend children over 6 months old receive a vaccination, especially before traveling internationally.

Fact checked by Sarah Scott

The number of confirmed cases of measles in the United States is on the rise. The Centers for Disease Control and Prevention (CDC) says between January 1 and March 14, 2024, there have been 58 confirmed cases of measles in 17 states. That's compared with a total of 58 cases in all of 2023.

The 17 states where measles cases have been reported are Arizona, California, Florida, Georgia, Illinois, Indiana, Louisiana, Maryland, Michigan, Minnesota, Missouri, New Jersey, New York City, Ohio, Pennsylvania, Virginia, and Washington.

This has prompted the CDC to issue a health alert to doctors and public health officials so they can provide guidance to their patients, especially those traveling internationally. According to the CDC's health alert, 54 of the 58 cases of measles have been linked to international travel. Therefore, the CDC is urging everyone, but especially those traveling abroad to make sure they are up to date with their measles-mumps-rubella (MMR) vaccines.

All of this comes after a measles outbreak in Philadelphia at the end of last year, affecting at least eight people. The outbreak began in December after a baby was admitted to Children’s Hospital of Philadelphia (CHOP), according to The Philadelphia Inquirer. That child had visited another country where measles is present.

According to reports, the disease spread from the child to three other people at CHOP, including a parent and an unvaccinated child. The Health Department reports that, despite being notified of quarantine protocol, the parents sent the child to daycare, where four more people became infected.

Meanwhile, the New Jersey Department of Health also confirmed a case of measles in January. Officials say the individual visited two health care facilities earlier in the month and also attended a daycare facility. County Health Officer Paschal Nwako said the department is conducting an investigation in order to locate those who may have come in contact with the patient. He cautioned that symptoms could develop as late as early February.

Measles, which can be fatal, was declared eliminated from the United States in 2000. However, outbreaks like this have occurred since, typically from unvaccinated travelers who bring the viral infection into the country. This can be tricky for medical professionals.

“Aside from the threat of the virus itself, the problem a measles outbreak presents is that most physicians have never seen it in the real world,” says Larnie Booker, MD, FAAP, a pediatrician at Advocare Mid-Jersey Pediatrics and Clinical Professor of Pediatrics at Rutgers Robert Wood Johnson Medical School in New Jersey. “Because of the effectiveness of vaccines, a majority of doctors have only read about measles in books or heard about it in lectures.”

Dr. Booker adds the “lack of tangible experience with the disease could potentially lead to delays in diagnosis, as well as slow the initiation of treatment and quarantine measures.”

But experts say vaccination is the best way for families to protect themselves.

What To Know About Measles

Measles is very contagious, and spreads through airborne respiratory droplets that can linger in the air for up to two hours. Research shows if a person has measles, 9 out of 10 unprotected people around them will also catch it.

An infection starts off like a typical cold; symptoms can include fever, cough, runny nose, fatigue, and conjunctivitis, along with whitish or gray spots on the inside of the cheek.

A characteristic red, spotty, and bumpy rash typically starts on the face and travels down toward the feet. Those infected with measles are usually contagious for four days before the onset of the rash, and four days after.

In most cases, the infection will simply run its course with pain and fever medications, such as Tylenol, and fluid support, says Paul K. Sue, MD, CM, FIDSA, pediatrician and associate professor of pediatrics in the division of pediatric infectious disease at Columbia University’s Department of Pediatrics.

“However, measles can also lead to serious complications, including otitis media, pneumonia, meningitis, diarrhea, and encephalitis, and leads to the death of one to three children for every 1,000 infections,” Dr. Sue adds.

Worldwide, there were about 136,000 measles deaths in 2022, and most were among children, according to the Centers for Disease Control and Prevention (CDC). Children under 5 are at the highest risk for infection and severity, explains Dr. Sue. People with certain underlying immunocompromised conditions are also at increased risk for infection and mortality.

Should Parents Worry About a Measles Outbreak?

The good news: the MMR vaccine is effective in protecting against measles, mumps, and rubella. It’s typically administered in children starting at the age of 12 months, with the second dose given at about 4 years old.

According to the CDC, the vaccine, which is made with a weakened live virus, is about 93% effective after one dose, and 97% effective after two doses.

While the vaccine typically provides lifelong immunity, “waning of the vaccine can occur but is rare, and happens in less than 5% of people, usually after a few years,” explains Dr. Sue.

In rare cases, fully vaccinated people could still contract measles, mumps, or rubella. Experts say in those few cases, it could be that their immune systems didn’t respond as well as it should have to the vaccine or their immune system’s ability to fight the infection decreased over time. But disease symptoms are generally milder in vaccinated people.

Dr. Sue points out that some people are not able to receive the vaccine, such as infants younger than 6 months, pregnant people, and those with immunocompromised conditions. “The vaccine is a living—albeit weakened—virus,” he says. “It can cause serious, even fatal disease, if given to these groups.”

This is why experts stress the importance of getting vaccinated against measles, especially as more cases have surfaced in recent years. According to the CDC, 1,274 individual cases of measles were confirmed in 31 states in 2019. It was the greatest number of cases reported in the U.S. since 1992, and the majority of cases were among people who were unvaccinated.

“Wherever we see clusters of infection, we find groups of unvaccinated or incompletely vaccinated people,” says Dr. Sue. “The lack of protection creates chains of transmission, and an unprotected population is a prime target for a potential outbreak."

Parents can speak with their child's health care provider to confirm their vaccine history and to learn about proper precautions if there has been any contact with an infected person. Always make sure to contact a health care provider if your child develops any concerning symptoms. And, as experts point out, it's best to keep kids home when they are sick.

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