Canada is on the brink of losing its measles elimination status as an outbreak that started a year ago continues to escalate.
The United States may not be far behind in the coming months.
The outbreak in Canada began in October 2024 in New Brunswick, which is located on the eastern coast of the country. As of Tuesday, over 5,000 cases have been logged, and tragically, two babies have died.
Canada had successfully eliminated measles back in 1998, with the U.S. following suit in 2000.
Several factors are considered when determining whether a country should forfeit its measles elimination status, including a decline in vaccination rates in both nations.
However, the most critical criterion is the presence of ongoing measles transmission for a full year.
“For a country to officially lose its status, it requires 12 months of continuous transmission with the same virus strain and genotype,” explained Daniel Salas, an immunization expert from the Pan American Health Organization (PAHO).
Canada has unfortunately reached that point this week.
PAHO, part of the World Health Organization, is the organization responsible for assessing measles elimination in countries across the Americas. They are scheduled to meet in Mexico City next week to review data on measles through the end of October.
If a country ends up losing its elimination status, PAHO will request a corrective action plan to help restore that status.
According to Salas, it’s quite unlikely that the U.S. will lose its elimination status in this upcoming meeting, as the current outbreak began only in January.
This year, at least 1,618 cases of measles have been recorded in the U.S., as reported by the Centers for Disease Control and Prevention. The impending threat to the U.S. elimination status originated in West Texas in late January, with over 800 individuals affected in Texas and New Mexico. The outbreak has since spread to other states, resulting in three deaths, including two young girls.
There will be a lag in determining whether the continuing cases in Arizona, Utah, and South Carolina are connected to the outbreak in West Texas.
Salas remarked that the elimination of measles in both the U.S. and Canada was a major accomplishment. “Sustaining elimination regionally means recognizing each country’s efforts,” he added.
The potential loss of elimination status for Canada serves as “a wake-up call that we need to improve public vaccination rates to prevent such outbreaks,” noted Dr. Isaac Bogoch, an infectious diseases expert from the University of Toronto, in a recent interview.
The measles-mumps-rubella (MMR) vaccine is highly effective, according to the CDC. Two doses, generally given around ages one and five, boast a 97% effectiveness rate at preventing infection.
