Measles outbreak threatens US status of ‘eliminating’ virus

The rash of measles outbreaks around the country has sparked concerns that the U.S. risks losing its status as a country where the disease has been eliminated, a distinction held since 2000.

As of last week, 41 measles cases have been confirmed across 15 states and New York City, according to the Centers for Disease Control and Prevention (CDC). That puts the nation already on track to surpassing the 58 total cases that were detected in 2023.

“I think the year is not off to a great start. And definitely I think there is concern that this trend will continue and that we will see more cases. It is early, but I think it is cause for concern,” said Sarah Lim, an infectious disease physician and member of the Infectious Disease Society of America.

Much of the attention concerning measles cases has focused on Florida, where 10 cases have been detected across two counties so far.

But infections also have been confirmed in states including Arizona, California, Georgia, Indiana and Maryland.

When reached for comment, the Florida Department of Health said in a statement, “While details of epidemiological investigations are confidential, many media outlets are reporting false information and politicizing this outbreak.”

The department emphasized that while vaccination rates are falling nationally, at least 97 percent of students at Manatee Bay Elementary in Weston, where most Florida measles cases have been detected this year, have received at least one dose of the vaccine.

The concentration of Florida’s cases in schools, as well as Florida Surgeon General Joseph Ladapo’s response to the outbreak, have drawn heightened scrutiny. In a letter to parents, Ladapo recommended keeping unvaccinated children at home for three weeks, as the CDC advises, but did not mandate it.

The CDC recommends people without immunity to measles should isolate after potential exposure for 21 days. Florida Rep. Debbie Wasserman Schultz (D) cited Ladapo’s letter as reason for him to be removed from his position.

In his letter, Ladapo referenced “the high immunity rate in the community” as part of why the state would not require unvaccinated students to stay at home. That high immunization rate affords the U.S. the status of being a country that has eliminated measles, but if outbreaks like the one in Florida keep happening, experts worry that could change.

“Once you’ve lost that status, it just means that cases are transmitting locally, which they are, not imported. And so we’re already in that status, where we have local transmission, and if it keeps on going up, we have to say it’s not eliminated,” said Monica Gandhi, professor of medicine at the University of California, San Francisco and associate division chief of HIV, Infectious Diseases, and Global Medicine. 

Comparable First World countries such as the U.K. have lost their measles elimination status in recent years, having only regained its status in 2021 after losing it in 2018.

As the CDC notes, the World Health Organization defines measles elimination as “the absence of endemic measles virus transmission in a defined geographical area (e.g. region or country) for at least 12 months in the presence of a surveillance system that has been verified to be performing well.”

“If a measles outbreak continues for a year or more, the United States could lose its measles elimination status,” the agency notes on its website.

Federal health authorities maintain a “Healthy People 2030” target of achieving 95 percent MMR (measles, mumps and rubella) immunization coverage. That rate among children has been on a slight decline since 2019, falling from the ideal 95 percent to 93.1 among kindergarteners nationally in the 2022-23 school year.

The CDC estimated this vaccination rate leaves roughly 250,000 kindergarteners at risk of a measles infection. Unlike vaccines for the flu or COVID-19, a complete schedule of the measles vaccine is nearly completely effective at preventing infections.

Lim emphasized that “eliminated” does not mean “eradicated.”

The COVID-19 pandemic has been blamed for interrupting vaccination rates among children, but Lim noted that an increase in people “catching up on travel” could concurrently be contributing to cases, as travelers return from countries where measles is not eliminated. 

According to Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia, two major events following the elimination of measles in the U.S. significantly impacted vaccination rates: the debunked study linking vaccines to autism, and the COVID-19 pandemic. Offit cites these as having bred sentiments adverse to public health.

“We leaned into this libertarian left hook, and you’ve seen now hundreds of legislative bills introduced to basically eliminate vaccine mandates, for masking mandates, for isolation mandates, quarantining mandates. It’s kind of, you know, this pushback against the weapons of public health, which are vaccination and isolation in the case of measles. And I think Florida represents that in a sense,” Offit said.

If people aren’t too concerned about a measles infection, Offit suggests it may be because they don’t have a good idea of what measles means, especially for children.

“I think not only have we largely eliminated measles, we’ve eliminated the memory of measles. I don’t think people remember just how sick measles can make you,” Offit said.

A measles infection usually presents with cold-like symptoms and a characteristic rash that forms a few days after symptoms begin. Offit emphasized that measles is “not a disease you want in a hospital” due to just how contagious it is, posing a threat to immunocompromised patients. 

“If you let your guard down, measles will come back. I am scarred by the 1991 Philadelphia measles epidemic,” Offit said, recalling how an outbreak originating from local religious communities quickly spread out into the surrounding areas, ultimately killing nine children. 

When asked what public health measure he would advise in light of the recent outbreaks, Offit, who recently authored a book on COVID-19 misinformation titled “Tell Me When It’s Over,” bluntly stated, “vaccination.” 

At 93 percent coverage, the U.S. can still boast a robust population protection against widespread measles outbreaks. But for people like Gandhi, the professor of medicine, any case of a vaccine-preventable illness is cause for concern. Gandhi notes the paralytic case of polio — also considered to be eliminated in the U.S. — that occurred in New York last year as an example of why strong population immunization is so important.

“The concerns are that these are vaccine-preventable illnesses. It can help high mortality rates, especially in children, and there’s just no reason for it,” Gandhi said. “I think it makes infectious disease people really weary and scared to see old diseases resurfacing when we have to not have that occur at all.”