Canadian health officials announced Monday that the country has lost its measles elimination status due to an outbreak of the infectious disease persisting in the country for more than a year, and the United States may not be far behind.

Officials said they received notice about the designation from the Pan American Health Organization, or PAHO, a branch of the World Health Organization, after it confirmed that Canada had seen sustained transmission of the same measles strain for more than 12 months ― one of the main metrics used to determine a country’s elimination status.

The change brings a nearly 30-year public health victory to a screeching halt. Canada first achieved elimination status in 1998, meaning the country had gone a year or more without continuous domestic transmission of a measles strain. The U.S. followed in 2000.

In just the first 10 months of the year, Canada has seen around 5,000 cases of measles across 10 jurisdictions. That’s compared to around 1,700 cases from an outbreak across the U.S., which has around eight times Canada’s population.

There were 23 new cases in the last week of October alone, Canadian officials noted.

The outbreak has resulted in two deaths, both of premature newborns infected while in utero.

“While transmission has slowed recently, the outbreak has persisted for over 12 months, primarily within under-vaccinated communities,” the Public Health Agency of Canada announced.

In both Canada and the U.S., the current outbreaks started in Mennonite communities, which were both severely undervaccinated.

Canadian officials urged uptake of the measles, mumps and rubella, or MMR, vaccine in their announcement Monday.

“The measles vaccine is the best way to protect you and your family,” the agency stated. “By staying vigilant and working together to increase measles vaccine coverage, we can prevent outbreaks and keep our communities safe against this preventable disease.”

Canada will not be able to claim elimination status again until the country has gone a full year without the strain from the current outbreak spreading.

Experts have warned for months that the U.S. may be on track to lose its measles elimination status, too. PAHO is expected to make that decision if cases linked to a Texas outbreak in January persist through the end of 2025.

Such a status change, which reflects the spread of a deadly disease that carries several long-term side effects, including permanent brain damage and hearing and vision loss, could make it more difficult for Americans to travel.

“It could affect U.S. citizens’ ability to travel to specific countries if they don’t want the risk of measles getting introduced to their country,” Brittany Kmush, associate professor and graduate director of Syracuse University’s Public Health Department, told HuffPost in July. “It could affect other people’s ability to come visit the U.S. Other countries might require proof of measles vaccination before they can reenter their home country.”

Health and Human Services Secretary Robert F. Kennedy Jr., a longtime anti-vaccine conspiracy theorist chosen for the role by President Donald Trump, has repeatedly spread misinformation about MMR vaccines, claiming earlier this year that people sickened by the measles virus may just lack “good nutrition” and a “good exercise regimen.” He’s also repeatedly pushed unverified treatments for measles and claimed people who derive natural immunity from the virus may gain protection from cancer and cardiac disease.

In June, researchers found that the MMR vaccination rate among American children had fallen around 3% since the start of the COVID-19 pandemic, lining up with the rise of anti-vaccine misinformation. That shift followed over a decade of more stable MMR vaccination rates, the study’s authors told HuffPost.