A measles alert sign outside the hospital in Woodstock, Ont., on March 18.Brett Gundlock/The Globe and Mail
More than 100 new cases of measles have been diagnosed in Ontario in the past week as a major, multijurisdictional outbreak spreads to new parts of the province.
Public Health Ontario’s latest surveillance report, released Thursday, notes 102 new cases of the viral illness – 92 of them confirmed, 10 of them probable.
The report also shows that the highly contagious virus has turned up in two new public health units: the Region of Waterloo and Lambton Public Health, which is home to the city of Sarnia.
“The sharp increase in the number of outbreak cases and the geographic spread in recent weeks is owing to continued exposures and transmission among individuals who have not been immunized,” the report says.
Ontario is in the grips of the worst measles outbreak since the vaccine-preventable disease was deemed eliminated in Canada in 1998. Public health leaders refer to an infectious disease as eliminated when the pathogen no longer circulates regularly in a particular geographic area.
On the ground in the epicentre of Ontario’s measles outbreak
The Ontario outbreak, which began in October, has been traced back to a Mennonite gathering in New Brunswick, according to a memo that Kieran Moore, Ontario’s Chief Medical Officer of Health, sent to local medical officers of health on March 7.
A total of 572 cases of measles are now connected to the outbreak. By way of comparison, 101 cases were logged in the entire decade between 2013 and 2023.
Most of the cases have been diagnosed in unvaccinated children. Forty-two people have been admitted to hospital for treatment of measles-related complications, 41 of whom were unimmunized. Thirty-six were children. Two people required critical care, one of them a child.
There have been no measles deaths reported in Ontario this year. A child under the age of five died of the illness in Hamilton last year.
“Over 90 per cent of cases in Ontario linked to this outbreak are among unimmunized individuals,” Dr. Moore wrote in his memo. “Cases could spread in any unvaccinated community or population but are disproportionately affecting some Mennonite, Amish and other Anabaptist communities due to a combination of under-immunization and exposure to measles in certain areas.”
The epicentre of the outbreak is in two neighbouring public health units called Southwestern and Grand Erie, which cover the small towns and farming communities south and east of London. Together, they account for 65 per cent of the cases reported since the outbreak began.
However, the latest report shows the virus is spreading beyond the original hotbed. Huron Perth is now reporting 55 cases, up from 42 the week before, while Chatham-Kent is reporting 39 cases, up from 20 a week earlier. They are the areas with the most cases after Southwestern (253) and Grand Erie (116).
Measles is making a comeback in other parts of Canada as well. Quebec is grappling with an outbreak that has reached 40 cases, while British Columbia, Alberta, Saskatchewan and Manitoba have diagnosed sporadic cases. New Brunswick reported 50 cases last fall as part of an outbreak that ended Jan. 7.
Experts blame the resurgence on a drop in routine vaccination rates since the pandemic, which made shots more difficult to access during health care system shutdowns. Political fights over lockdowns, masking rules and vaccine mandates, supercharged by online misinformation, also contributed to suspicion of vaccines.
As a result, measles is surging around the globe, according to the World Health Organization. Europe reported 127,350 cases last year, twice as many as in 2023 and the most in 25 years.
Officials with the Southwestern Public Health Unit have been working to boost immunization coverage since early March, when 115 new cases were reported. The outbreak has since grown.
The Canadian Press