Texas measles outbreak could last 12 months, experts say, risking U.S. elimination status

The measles outbreak that began in West Texas more than two months ago could continue spreading and growing for months to come, according to health experts.

The outbreak has already caused the state to report more measles cases in the first few months of this year than in any full year since 1992. There have been 481 cases reported in Texas alone, as of Friday, plus dozens of additional cases in two neighboring states.

Health officials have also reported the deaths of two unvaccinated children.

It’s difficult to predict how long the outbreak could last, health experts said. But Lubbock’s public health director, Katherine Wells, worries it could be many more months still.

“I’m really thinking this is going to be a year-long in order to … get through this entire outbreak,” Wells said in a mid-March news briefing.

Other health experts, while hesitant to give an exact timeframe, agreed the outbreak still has a long time left.

“I don’t think this thing is anywhere near over yet,” said Dr. Greg Poland, a vaccinologist, in late March.

Measles was declared eliminated in the U.S. in 2000. The World Health Organization defines measles elimination as the “absence of endemic measles transmission” for at least 12 months. That means the U.S. could lose its elimination status if a measles outbreak lasts longer than a year.

“We are almost certainly going to lose that,” Poland said. “In that sense, from a public health view, we are going backwards. And that will hurt people.”

A ‘continuing engine of cases’

Measles is among the most contagious illnesses in the world, and it spreads rapidly among unvaccinated people. That makes it difficult to contain once it takes hold in communities with low vaccination rates.

Amy Winter, an assistant professor at the University of Georgia’s College of Public Health, said in a news briefing that a measles outbreak can infect up to 95% of a susceptible—or unvaccinated—population.

“It can be very, very large,” Winter said.

Dr. Simbo Ige, the commissioner of the city of Chicago’s public health department, put it another way: the outbreak will continue to grow as long as there are unvaccinated people in its path.

“As long as we continue to have a pool of unvaccinated people, it will continue to spread,” Ige said. “It’s very hard to say it has peaked unless you have successfully vaccinated everyone who is unvaccinated.”

The exact length of a measles outbreak is difficult to predict ahead of time, multiple health experts said.

It depends on how many unvaccinated people decide to get vaccinated, and on how much infected people travel or interact with others while they’re contagious.

In the case of Texas’ outbreak, Poland pointed to fierce anti-vaccine advocates—such as Fort Worth’s Mercy Culture Church, whose pastor recently celebrated its school’s low vaccination rates—as a “continuing engine for cases.”

The length of the outbreak is extended by about two weeks each time a state reports a new case, said Dr. Peter Hotez, a vaccine expert and the dean for the National School of Tropical Medicine at the Baylor College of Medicine. That lag is due to the incubation period of the virus.

Both Poland and Hotez said they’re worried the Texas outbreak—which has already spread to three states—could spread further to states with low vaccination rates.

Hotez pointed specifically to Idaho. For the 2023-24 school year, Idaho was the state with the lowest rate of kindergartners fully vaccinated against measles, according to data from the U.S. Centers for Disease Control and Prevention.

“If it starts going north, the biggest worry of all is that it hits Idaho,” Hotez said. “And it’ll just rip through Idaho, so that that could give it new life as well.”

The only way to truly stop the outbreak is to increase vaccination rates, multiple public health experts said.

“The measles vaccine is safe, it’s effective, and measles transmission in the United States is driven by failure to vaccinate,” Winter said.

Threat to elimination status

The fight against measles in the U.S. was won, for all intents and purposes, a quarter century ago.

High vaccination rates stemmed the virus’ spread and led to the elimination the illness. There continued to be outbreaks and individual cases, but not widespread illness or infections.

The country came close to losing its elimination status in 2019, when a large measles outbreak took hold in two Orthodox Jewish communities in New York. Those two outbreaks, which were related to each other, totaled more than 1,100 cases over the course of 2018 and 2019.

Health experts don’t yet know if the outbreak that began in Texas will eventually lead to the country losing its elimination status.

But it’s a possibility, said Dr. William Moss, the executive director of the International Vaccine Access Center at Johns Hopkins, in a mid-March news briefing.

“It’s hard to say right now whether this outbreak is going to continue for 12 months,” Moss said. “But it does remain a threat, and we potentially could lose our measles elimination status if this continues the way it has.”

Health officials and experts have stressed vaccination is the best defense against measles. The two-dose measles-mumps-rubella vaccine is 97% effective at preventing illness.

The vaccine is recommended for nearly everyone, beginning with babies at about 12 months of age. People who are pregnant and immunocompromised are not advised to take the vaccine.

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