Texas and New Mexico health departments said on Friday that the number of measles cases in their states rose 20% since their last reports three days ago, as experts warn they expect the outbreak to further spread in coming weeks.
Texas now has 400 cases, the Texas Department of State Health Services said, 270 of which were in Gaines County, where the current measles outbreak started. Texas has reported two deaths from measles since this outbreak began.
New Mexico reported one additional case, bringing its total count to 44. Kansas and Oklahoma have also linked local outbreaks to the Texas cases.
The U.S. Centers for Disease Control and Prevention, whose data is one day behind the Texas and New Mexico report, said there were a total of 483 confirmed measles cases as of March 27, a jump of 105 from a week earlier.
Infectious disease experts said the magnitude of the outbreak's acceleration was uncertain, but it was clear that more cases would emerge. The number of U.S. measles cases so far this year has already exceeded those reported for all of 2024.
Dr. Sapna Singh, chief medical officer for Texas Children's Pediatrics, said the worry is that cases are "still continuing active spread in those areas of outbreak that we're not even catching." She warned that holiday gatherings and travel could seed more infections.
Experts have warned that declining U.S. vaccination rates can make the population vulnerable to highly contagious measles.
The disease, which can be especially serious in young children, was considered eradicated in the U.S. in 2000. But vaccination rates have since fallen, and just 80% of those in the Texas county where the outbreak began were inoculated against measles, well below the 95% needed for so-called herd immunity.
Dr. Amesh Adalja, an infectious disease expert at the Johns Hopkins University Center for Health Security, said he expects rates to rise in the next several weeks either because of the pace of infections or the pace of diagnosis as more resources are poured into that community.
"When you're in a population that has low vaccination rates, and you're dealing with a virus like measles, the general consensus is that this is going to take some time to quench and it's going to continue to spread rapidly until that virus runs out of people to infect," he said.
U.S. Health Secretary Robert F. Kennedy Jr., who for years has sown doubts about the safety and efficacy of vaccines, has said curbing the Texas measles outbreak is a high priority. But he stopped short of urging people to get vaccinated, despite decades of evidence that immunization is the best protection against the measles virus.
As of March 26, Kansas had reported 23 cases, and according to the state health department, genetic sequencing showed the first case had an epidemiological link to Texas and New Mexico.
Also Wednesday, the Ohio Department of Health said the state has identified 10 measles cases. Nine of those infections have been linked to the first case in the state who had contact with someone who had recently traveled internationally.
Dr. William Schaffner, an infectious disease expert at the Vanderbilt University Medical Center, said travel in and out of the affected community in West Texas means there will probably continue to be "daughter outbreaks" in neighboring areas.
"Each of those other little outbreaks, depending upon the communities in which they occur, could also spread," he said.
