Listen to this article
Estimated 4 minutes
The audio version of this article is generated by AI-based technology. Mispronunciations can occur. We are working with our partners to continually review and improve the results.
The number of measles cases in the U.S. this year has already surpassed the record-breaking tally for all of 2025.
The U.S. Centers for Disease Control and Prevention logged 2,318 cases of measles as of Thursday, according to an agency update on Friday.
The U.S. had 2,289 cases in 2025, the worst year for measles in more than three decades. Now, with five months still to go, 2026 has easily become the country’s worst year for measles since 1991 — as major outbreaks in South Carolina, Utah and Arizona have sickened hundreds and smaller clusters of cases sparked in other states.
In Canada, 1,102 measles cases have been reported so far this year, according to Health Canada’s most recent update. Most are children. In 2025, due to an outbreak that cost Canada its measles elimination status, 5,462 cases were reported.
In November, international health officials will meet to determine if the U.S. and Mexico have lost their measles-free status. The U.S. eliminated local measles spread in 2000 by maintaining high vaccination rates, which have fallen in recent years to below the 95 per cent coverage needed to prevent outbreaks.
The Manitoba government is inviting residents in the Southern Health region to take part in a telephone town hall about measles. The area of the province has the highest concentration of measles cases in Canada.
Cases are undercounted
While measles cases in the U.S. are climbing, it may be impossible to say exactly how far-reaching the spread is. Public health departments and disease researchers have long acknowledged that official counts are incomplete, because some people get sick and don’t seek treatment — something not unique to measles.
Furthermore, experts say the spread might be greater than what’s known because the virus is one of the most contagious known to medicine and vaccination rates nationwide have declined. National vaccination rates for measles, mumps and rubella — which dropped to 92.5 per cent among kindergartners in the 2024-25 school year, from 95.2 per cent in 2019-20 — obscure even lower rates in certain communities.
In Utah, where public health officials have fought measles for more than a year, the virus has sickened more than 700 people during that time, according to the state health department. Experts relying on mathematical modeling and genetic analyses indicate that a large outbreak on the Utah-Arizona border could be around three to four times bigger than what’s currently known, state epidemiologist Dr. Leisha Nolen said.
The picture is muddier in South Carolina, which had the nation’s largest outbreak in 35 years. There, the 997 total is likely an undercount, the state health department has said, but it doesn’t know by how much.
Dr. Brannon Traxler, acting director of the state department of health, said the undercount is “impossible to know and may vary during the course of an outbreak.”
Data gaps can make it hard to reliably estimate an outbreak’s true scope. Experts say hospitalization rates can be a good barometer, but measles hospitalizations are not required to be reported in every state.
“If we really had some kind of solid-gold standard for the percentage of all cases that have hospitalization or some measure of severity, then that would be another way of estimating the outbreak size that we could see if it’s consistent with these other methods,” said Damon Toth, an applied mathematician at the University of Utah’s medical school who is working on one of the Utah outbreak analyses.
‘Innocent bystanders’
Dr. Mark Roberts, retired director of the Public Health Dynamics Lab at the University of Pittsburgh School of Public Health, worries most for the people he calls “innocent bystanders.”
Research and measles modeling by his team shows those who cannot get vaccinated — young babies, people with weak immune systems and those who rarely don’t get robust immunity from the vaccine — bear the brunt of outbreaks early on.
Some people see skipping vaccination as like deciding not to wear a seat belt in a car, Roberts said.
“Not vaccinating your kid is like saying, ‘I don’t want my car to have brakes,'” he said. “Because it’s other people that you can hit. It’s not just you in your car. It’s other people.”
A CBC News analysis shows childhood vaccination rates appear to be declining in B.C. The trend comes as a measles outbreak makes its way through northern B.C. The CBC’s Jon Hernandez takes a closer look at the numbers.
About the Author
