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In the early 1960s, American children lined up to receive the world’s first measles shots, but it took nearly 40 years to ramp up immunization programs until the notorious epidemic was thoroughly controlled. In 2000, a panel of experts declared that the United States had eliminated measles from within its borders.
For a quarter of a century, the United States has seen outbreaks only when infected travelers brought the virus from abroad. The resulting measles epidemic lasted less than a year.
Those days are over.
Measles began ravaging the dusty plains of West Texas last January and has since caused cases in all but a handful of states. Two unvaccinated Texas girls and a New Mexico adult who crossed the border died last July, before the West Texas outbreak appeared to be over.
By then, Utah had experienced a measles outbreak, and state health officials could not determine where the first patient contracted the virus. The state’s outbreak began that fall and winter and continued into May of this year.
The Texas and Utah cases are now at the center of the unusually technical and politically arcane question of whether the United States will lose its measles eradication distinction.
Countries are not penalized for losing eligibility, but they indicate either cracks in their once-solid immunization programs, a lack of trust in vaccines among their citizens, or both.
To have a chance of retaining the designation, the United States would have to make a strong case that measles was not endemic, that is, spread from person to person in continuous chains within the country over a period of more than a year. For example, if the Texas virus traveled across the Southwest to Utah and continued to infect people there, that would be a problem. But if the Utah outbreak was caused by a patient who contracted measles overseas, it would create a new chain of events and restart the clock.
To find clues, the Centers for Disease Control and Prevention is analyzing the complete genetic code of the measles virus that infected patients. Last November, CDC leaders at the time said preliminary genomic analysis suggested the Utah cases were not directly related to the Texas cases. A spokesperson for the Department of Health and Human Services told ProPublica that the work was done by the state lab and that the CDC is conducting a more comprehensive investigation.
ProPublica undertook its own analysis, examining more than 1,800 whole-genome sequences, including those released as recently as last month, to compare the genetic fingerprints of measles viruses circulating in the United States and Canada. This showed that the measles virus still circulating in Utah as of May of this year is very closely related to the measles virus that sickened Texans more than a year ago.
ProPublica’s analysis is not conclusive proof of endemic spread. From this information, it is impossible to determine whether the virus spread from state to state or whether it was brought in by a sick traveler who left the country at some point.
But given how similar the sequences of the viruses identified by ProPublica are, it will be difficult for the U.S. to prove that measles is not endemic — “unless the CDC does something about it,” said Dr. Alberto Severini, a former molecular virologist and measles expert who worked for the Public Health Agency of Canada for 20 years.
The unique fingerprint of mutations is not limited to these conditions. The five mutations observed in Texas and Utah were also present in the CDC’s published sequences of viruses that infected patients in Iowa, North Dakota, Minnesota, and Alaska last May and June.
But it’s not clear whether the genetic fingerprint is unique to the United States. Even in Mexico and the Canadian province of Ontario, where measles is most prevalent, the full genome sequences of cases have not been made public.
This is important because a key question facing a panel of experts convened by the Pan American Health Organization is whether the virus has been circulating continuously in the United States for more than a year, rather than spreading abroad and being brought into the country by travelers.
PAHO, the World Health Organization’s regional office, will decide whether the United States retains its measles-free designation. Canada lost that position last year. PAHO asked the US to make its case in April, but US officials asked for more time to investigate how the virus spread. Review modified in November.
PAHO official Daniel Salas said a thorough analysis like the one the CDC is conducting “takes time.”
“What the U.S. is trying to do with this whole-genome sequencing is ultimately to find some patterns that might allow us to say, for example, that mutations of this virus originated in a different country, a different place than the current outbreak that we’re analyzing. Ultimately, that might be taken into account and somehow replace the missing epidemiological information,” he said. “No country has ever done anything like this.”
One of the biggest questions is how the virus got into Utah. Health officials have determined that the first confirmed case, identified last June, could not have contracted measles in another country or state. Utah state epidemiologist Dr. Leesha Nolen said she and her team investigated the area where the patient was and the people who were around him, but could not yet determine where he contracted the virus.
The findings suggest that measles was quietly spreading in the area. A CDC disease detective investigating the subsequent incident, which straddles the Utah-Arizona border, said there were reports of a rash in the community last June, but patients refused measles tests and family members were often reluctant to answer questions.
Nolen said there were no interviews throughout the outbreak that suggested patients were infected in other countries, but she and her team can’t rule out that possibility.
ProPublica asked the CDC whether epidemiologists have linked Utah’s measles cases to international outbreaks, but the agency would not say, nor would it directly comment on the genetic similarities ProPublica found between the Texas and Utah viruses. “Sequencing alone cannot determine whether the infection is ongoing or persistent,” a spokesperson said in a written statement.
While genomic analysis may provide clues, the spokesperson wrote, “These findings must be interpreted in conjunction with epidemiological data, including travel history, exposure information, and known outbreak links.”
A spokesperson said the CDC is still working on a “comprehensive analysis of potential links between cases and outbreaks” and gathering additional epidemiological data, but did not elaborate on what that would show.
As the midterm elections approach, the measles outbreak has become a political liability for President Donald Trump, who chose the founder of an anti-vaccination group to be his health secretary. Since President Trump took office last year, more than 4,300 people have been infected in the United States, the highest number in 30 years.
Eliminating the spread of endemic measles is the public health equivalent of slaying the dragon. This disease is one of the most contagious diseases humans have ever encountered. Patients are contagious even before an obvious rash appears, and the infection can remain indoors for up to two hours after leaving the room.
Policymakers built the U.S. immunization system on lessons learned from the measles epidemic. To achieve the very high vaccination rates needed to prevent the spread of the disease, states required vaccinations for school and day care attendance, and the federal government provided free vaccinations to low-income children. While measles was still raging, state legislatures in California and New York cracked down on school exemptions. The United States helped other countries eliminate measles not only to prevent deaths, but also because those in power recognized that a disease that was contained overseas was unlikely to return to the United States.
During previous outbreaks in the U.S., health and political leaders spoke unwaveringly urging Americans to vaccinate their children and assuring them that the shots were safe.
President Trump and Health Department Secretary Robert F. Kennedy Jr. have not followed that strategy. Both have fueled questions about the safety of the MMR shot, which prevents measles, mumps and rubella.
Researchers around the world have found that vaccines do not cause autism. Nevertheless, at a press conference on autism last fall, President Trump said he had heard for years that combination vaccines have problems and urged parents to vaccinate their children separately, even though no single shot exists in the United States.
President Kennedy has said that vaccines protect against measles, but has repeatedly claimed that vaccination is more dangerous than measles.
“There are adverse events from vaccines,” he told Sean Hannity on Fox News last year. “There are deaths every year.”
Kennedy said on the podcast that when he contracted the virus as a child, he had to watch TV for a week. “I got chicken soup and vitamin A, which no one can patent,” he said.
Measles kills 1 to 3 of every 1,000 people infected and can cause hearing loss, intellectual disability, and swelling of the brain. In a “Know the Facts” post, the Infectious Diseases Society of America said there have been no deaths associated with vaccination in healthy people. The medical society explained, “We recommend that children with weakened immune systems not receive vaccines because there are rare cases of death from side effects of vaccines.” “That’s why it’s so important that everyone who can get vaccinated gets vaccinated to protect those who can’t get vaccinated.”
HHS spokesman Andrew Nixon said in an email that President Kennedy “believes that Americans have a right to clear information about both the benefits and risks of medical products so that they can make informed medical decisions in consultation with their health care providers.”
President Nixon said that “heavy-handed orders” during the coronavirus pandemic were a contributing factor to the significant loss of trust in medical institutions. “The Secretary maintains that public health agencies will rebuild trust through honesty, transparency, and respect for individual choice rather than coercion,” President Nixon wrote.
President Kennedy is trying to distance himself and his administration from a resurgence of measles. He said the United States has done a better job of containing the spread than any other country, noting that Canada and Mexico, which have much smaller populations, have far more cases.
“Instead of repeating the same tired stories, fake news reporters should spend more time examining why the Trump administration’s efforts to stop the measles outbreak in the United States have been so much more successful than in Canada and Mexico,” White House press secretary Khush Desai told ProPublica.
Kennedy also reminded lawmakers that the outbreak in Texas began before he became health secretary.
“There is a global pandemic going on,” he told senators in April. “That doesn’t concern me.”
Kennedy has been one of the most prominent voices in the anti-vaccination movement for more than a decade.
Dr. Adam Ratner, a pediatric infectious disease physician who wrote a book on measles, said President Kennedy “did everything in his power to undermine confidence in America’s vaccines.”
During the 2018 measles outbreak in New York City, Ratner treated at least five hospitalized unvaccinated children, including a couple who needed intensive care, so she knows that not all children can escape the disease with screen time and memories of soup.
While most parents still support vaccination, Ratner worries that the country no longer has the capacity to embrace the policies that once stopped the spread of epidemics. Rather than tighten vaccination requirements in schools, some states are moving to eliminate vaccinations altogether in the name of medical freedom.
“We need a high level of vaccination of the population to control the spread of infection,” he said. “If we don’t do that, I think the infection will continue to spread and we will have tragedies like what we saw in West Texas where two children died.”
There’s a good chance the United States will find the international travelers it needs to prove its country is measles-free. But if everything remains the same, experts say it will only delay the inevitable.
“The fact remains that measles transmission has been ongoing in the United States for more than a year,” Severini said. “If people don’t get vaccinated, measles will become endemic.”
