Once considered eliminated in the U.S. because of wide vaccine availability, measles cases are climbing. By mid-March, the case count for 2024 was higher than last year’s total, at 64 with the possibility of more to come, according to the Centers for Disease Control and Prevention. There were 58 U.S. cases in all of 2023.

In 2024, measles has been reported in 17 states, coast to coast: Arizona, California, Florida, Georgia, Illinois, Indiana, Louisiana, Maryland, Michigan, Minnesota, Missouri, New Jersey, New York, Ohio, Pennsylvania, Virginia and Washington.

Recent totals, though, are still far below the yearlong outbreak in 2019 that saw a total of 1,274 confirmed cases across 31 states.

The CDC issued a health advisory on March 18. “Ensure children in the United States and those traveling internationally 6 months and older are current on MMR vaccination,” it read, noting an increase both in the U.S. and globally.

Symptoms and complications

The measles (rubeola) virus is extremely contagious, with a 90% chance that someone who has no protection from vaccination will get it if exposed. “One person infected with measles can infect 9 out of 10 unvaccinated individuals with whom they come in contact,” the warning said. It further noted “high population immunity against measles in most U.S. communities,” which should keep spread low. “However, pockets of low coverage leave some communities at higher risk for outbreaks.”

Prior to vaccine availability, the CDC reported that as many as 4 million people were infected annually. “Also each year, among reported cases, an estimated 400 to 500 people died, 48,000 were hospitalized, and 1,000 suffered encephalitis (swelling of the brain) from measles.”

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Measles was declared eliminated in the U.S. in 2000 — a designation that didn’t mean no cases of the virus, but rather “absence of continuous disease transmission for greater than 12 months,” per the CDC.

Measles can be dangerous, particularly for babies and young children, beyond the usual symptoms of high fever, cough, runny nose and red, itchy eyes. Those symptoms may not begin to appear for a week or more after exposure, then are followed a couple of days later with what are called Koplik spots, which are little white spots in the mouth that may hurt. A day or two later, the hallmark measles rash shows up, typically starting at the hairline and then heading downward.

Among those who were not vaccinated and who get measles, about 1 in 5 end up hospitalized. Among young children, 1 in 20 develop pneumonia, which accounts for the most deaths among young children.

Complications, per the CDC, are more often seen in kids younger than 5, adults older than 20, pregnant women and people with compromised immune systems. Common complications include ear infections and diarrhea. Severe complications include pneumonia and encephalitis. Children can lose their hearing or develop intellectual disability. “They may need to be hospitalized and could die,” the CDC reports. Unvaccinated pregnant women may deliver prematurely or have a low birth-weight baby and challenges related to that.

A long-term complication called subacute sclerosing panencephalitis can also develop. Though very rare, it’s fatal. The condition develops around seven to 10 years after someone has apparently recovered completely from measles.

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Vaccination rate down

The CDC advisory said that the vaccination rate among U.S. kindergarten students has decreased from 95.2% in the 2019-2020 school year to 93.1% in the 2022-2023 school year, which is below the 95% herd immunity protection rate, leaving close to a quarter-million kindergartners at risk of contracting measles. The advisory said that 36 states and the District of Columbia had less than 95% of kindergarteners vaccinated last year. Of those, 10 states said more than 5% had medical or nonmedical exemptions, “highlighting the importance of targeted efforts that increase vaccine confidence and access.”

The notice continued, “Getting MMR vaccine is much safer than getting measles, mumps or rubella.”

There are exceptions. As The New York Times reported, “Doctors may recommend against vaccination for certain people with compromised immune systems, like those undergoing chemotherapy.”

Parents who are concerned about vaccine safety ought to talk to a doctor they trust, Dr. Demetre Daskalakis, director of the National Center for Immunization and Respiratory Diseases at the CDC, told the Times. But he acknowledged that vaccine hesitancy is real and overcoming it is “an uphill battle.”

“Given the impact on vaccine confidence that we’ve seen after COVID and during COVID,” he said, “I think we have to just keep that drumbeat going.”

During the 2019 outbreak, Rich Lakin, immunization program manager in the Utah Department of Health, told the Deseret News that for years the U.S. didn’t see measles cases, but now “we see them all the time. And there’s a strong correlation between the increase in exemptions and measles outbreaks.”

Concerned by the rapid rise in nonmedical exemptions to vaccination, the American Academy of Pediatrics lobbied to eliminate them. As the Deseret News reported at the time, “Nonmedical exemptions include those based on religious or personal beliefs about vaccinations, for example.”