A measles outbreak in New Brunswick that began with a single infected traveller has now spread to 44 people, most of them unvaccinated children who caught the highly contagious virus at a time when measles is surging around the world.
The outbreak, which was declared Nov. 1 in the Fredericton and Upper Saint John River Valley area, is the largest the province has seen in more than 30 years, according to Regional Medical Officer of Health Mark McKelvie.
More than 80 per cent of the cases have been diagnosed in people under the age of 19, and all of the patients were considered “susceptible” to the measles virus, Dr. McKelvie said. That means they were either unvaccinated or had an immunocompromising condition that would make the measles shot less effective. Three patients were admitted to hospital and have since been released.
The New Brunswick outbreak is part of a national and international measles surge after the height of the COVID-19 pandemic, which disrupted the delivery of routine childhood shots and inflamed anti-vaccine sentiment.
The World Health Organization and the U.S. Centers for Disease Control and Prevention reported last week that there were an estimated 10.3 million cases of measles around the globe last year, a 20-per-cent rise from 2022.
The Public Health Agency of Canada, meanwhile, has reported 100 cases of measles so far this year, but that tally is certain to grow because it only includes cases up to Nov. 2, when just five had been reported in New Brunswick. The last time the country logged more than 100 cases of measles was in 2019, when there were 103 cases nationwide.
Canada also recorded a rare death from measles this year in an unvaccinated child under the age of 5 from Hamilton.
“Unfortunately, the COVID-19 pandemic did really disrupt all health care, including vaccine delivery systems, and so there were more kids who got behind,” said Laura Sauvé, a pediatric infectious-disease physician, clinical assistant professor at the University of British Columbia and the president-elect of the Canadian Pediatric Society.
As well, she added, “there is a lot of messaging trying to increase the skepticism and fear around vaccines. There’s no scientific basis for those stories, but I think social media really, unfortunately, helps inflame and promote some of the misinformation that is out there.”
In New Brunswick, where parents have to supply proof that their children have received their routine immunizations to start public school, vaccination rates have held steady over the past couple of years, Dr. McKelvie said.
The province’s most recent school immunization report shows that approximately 91.2 per cent of New Brunswick students entering school in the 2023-24 academic year were immunized with two doses of the vaccine that protects against measles. That figure was nearly unchanged from 91.4 per cent the year before.
“So while our rates stay the same, there might be certain segments of the population who might not be getting vaccinated,” Dr. McKelvie said. “They might have gotten partial vaccination before, or sporadic vaccination, and now might have no vaccination.”
As measles cases rise around the world, particularly in European countries where Canadians frequently travel, the odds increase that the extremely contagious virus will more often hitch a ride on a plane and find pockets of friends and family who eschew vaccines.
How many of those measles-susceptible pockets exist and where they are is difficult to pinpoint in Canada, said Allison McGeer, an infectious-disease physician and researcher at Mount Sinai Hospital in Toronto.
She lamented that the Public Health Agency of Canada’s national metrics on vaccine uptake are based on survey data that are less precise and reliable than a national vaccine registry would be. “It’s better than nothing,” Dr. McGeer said, “but still, we’re a global embarrassment.”
PHAC’s most recent estimate, based on a 2021 survey, is that 91.6 per cent of two-year-old children in Canada have received at least one dose of the vaccine that protects against measles, less than the country’s 95-per-cent coverage goal.