Canada loses its measles elimination status. Will the U.S. be next?

Canada has lost its measles elimination status, the country’s Public Health Agency announced Monday, because of its inability to control an ongoing outbreak of the virus for at least a year.

A World Health Organization group “reviewed recent epidemiological and laboratory data, confirming sustained transmission of the same measles virus strain in Canada for a period of more than one year,” the Public Health Agency of Canada said in a statement.

Canada eliminated measles in 1998, two years before the U.S.

As of Monday, the country’s health officials had tallied 5,138 measles cases since October 2024. The outbreak began in New Brunswick, a province on the country’s eastern seaboard. Two babies, infected in utero, were born pre-term and died.

The U.S. is also on the brink of losing its measles elimination status, as an outbreak that began in January continues to spread across the country.

The outbreak started in West Texas and stretched into New Mexico. At least 862 people — mostly in Texas — were infected. Three people died. Two were little girls who lived in the epicenter of the outbreak, Gaines County, Texas.

Though cases have subsided in West Texas, the virus has continued to spread. Utah and Arizona are seeing an outbreak concentrated in a close-knit community that straddles the border between the states.

As of last week, 1,681 measles cases had been confirmed in the U.S. in 2025, according to the Centers for Disease Control and Prevention, the most in more than 30 years.

Who determines a nation’s measles elimination status?

The Pan American Health Organization (PAHO), part of the WHO, determines whether a country in North, South or Central America has maintained or lost its elimination status.

In 2019, PAHO established a panel of independent experts, called the Regional Verification Commission, to do an annual review of how countries are able to control measles spread.

The panel met last week in Mexico City to analyze the latest measles data submitted from countries with active outbreaks through October.

There are multiple criteria for losing an official measles elimination status, including declines in vaccination rates. The most significant factor is ongoing measles transmission of the same strain of the virus for a full year.

Canadian health officials will now have to come up with a plan to get back on track, including improving vaccination rates and “enabling better overall surveillance efforts,” the agency wrote.

Measles is the most contagious virus known on the planet. The virus can linger in the air for up to two hours after an infected person leaves the room. Anyone in that room who hasn’t been vaccinated against measles will likely get sick.