After returning home from a trip abroad last week, an infant in Houston was hospitalized with measles.
In Lamoille County, Vermont, this month, a child became sick with measles after returning from foreign travel.
The same thing happened to an adult in Oakland County, Michigan, whose vaccination status was unknown.
Although measles was declared eliminated in the United States in 2000, it still rages on in many parts of the world. With decreasing vaccination rates across the US, experts say, imported cases can have large consequences.
“Each one of those imported cases now is like a match being thrown into a bit of forest,” said Dr. Brian Ward, associate director of the JD MacLean Tropical Disease Center at McGill University. “The susceptible people in our communities now are like that accumulating fuel in a forest.”
Often, these illnesses happen “because a US resident goes outside of the US and is exposed and brings measles back. And I think that’s something that’s been happening for a while, and we’re certainly seeing … an upward trend in the last couple of years,” said Dr. Matthew Ferrari, director of the Center for Infectious Disease Dynamics at Penn State University.
The Texas health department does not know how the first person in the outbreak was exposed to the virus, said Lara Anton, senior press officer for the Texas Department of State Health Services.
Although the agency says the person had not traveled internationally, local officials speculate that they could have been exposed to someone else in the community who had.
“With the first reported cases being children who did not travel, they were likely infected by someone in their community. We don’t know who could have brought it in, but it would most likely come from international travel,” said Katherine Wells, director of Lubbock Public Health.
Measles is highly contagious and can linger in the air for two hours after an infected person has left the room. Due to the way it can spread, the state health department does not believe officials will ever know how the outbreak began, Anton said.
Measles surges abroad
Measles is on the rise around the globe. There were more than 12,500 cases reported in January, according to the World Health Organization, and cases for February and March are still being counted.
“There’s measles everywhere. Unfortunately, we have not been able to eliminate measles globally,” said Dr. Carlos del Rio, an infectious disease expert and distinguished professor of medicine at Emory University.
Last year, the number of cases in the European Region, which includes parts of central Asia, were the highest in 25 years, according to a report released last week by WHO and the United Nations Children’s Fund (UNICEF).
In 2023, 57 countries were affected by “large or disruptive” measles outbreaks, up from 36 in the year before, according to the US Centers for Disease Control and Prevention. These were mainly centered in Africa and the Eastern Mediterranean. There were 10.3 million measles infections globally that year, a 20% increase from 2022, according to WHO.
Experts say that this increase is driven by undervaccination, a problem that was heightened when the Covid-19 pandemic halted many childhood vaccination efforts. Undervaccination is especially relevant in conflict zones and under-resourced countries, according to experts, but other areas are beginning to see declining vaccination, too.
In lower- and middle-income countries, there is an “added burden of susceptible individuals on the background of poor delivery and lack of access in these areas with social disruptions,” Ward said. “Unfortunately, [there’s] vaccine hesitancy and refusal of vaccination in wealthier countries.”
Experts say the level of undervaccination around the globe can have stark effects at home.
“For the United States, measles is only a plane flight away,” said Dr. David Higgins, a pediatrician at the University of Colorado Anschutz Medical Campus. “If an American who is unvaccinated goes and travels … anywhere in the world where measles has increased, they [could] bring it back. … And I think we underappreciate, here in the United States, the degree of measles vaccine disruption around the world.”
US cuts global health funding
Controlling measles abroad – and consequently the number of imported cases in the US – could become more difficult with recent global health funding cuts, experts said.
A WHO network of more than 700 labs around the world that’s responsible for identifying measles and rubella cases faces “imminent shutdown,” Director-General Dr. Tedros Adhanom Ghebreyesus said.
Information from the Global Measles Rubella Laboratory Network (GMRLN), which was funded by the US, is often used to decide where measles outbreak resources should be designated, Ferrari says.
“The health of Americans very much depends on our abilities to know where measles is, so that we can appropriately protect and caution travelers,” said Dr. Jennifer Nuzzo, director of the Pandemic Center and professor of epidemiology at Brown University. “If measles surveillance erodes, it will just get harder to stop outbreaks … which will lead to more measles occurring on the planet, and it will get harder to know where those outbreaks are occurring, and it will get harder to keep measles out of the US.”
As case numbers rise both globally and within the US, there is increased an need to control the virus, according to experts.
“There’s really no distinction. Diseases don’t take breaks, and they don’t stay put. So, in this case, in this interconnected world, what happens in one country very much influences another country,” Nuzzo said. “Trying to protect the United States against measles, particularly while we still have our elimination status, very much depends on measles being controlled in other parts of the world.”