TORONTO — An infant born prematurely and infected with measles has died in southwestern Ontario, Dr. Kieran Moore, Ontario's chief medical officer of health, said Thursday.
The baby was infected with the virus while in the womb through their mother, who was not vaccinated, he said.
"While measles may have been a contributing factor in both the premature birth and death, the infant also faced other serious medical complications unrelated to the virus," Moore said in a statement.
"Out of respect for the family’s privacy, no further personal or medical details will be shared," he said.
This is the first death reported in Ontario's current measles outbreak, which began in October with a travel-related case in New Brunswick.
Ontario Health Minister Sylvia Jones called the death "deeply disturbing" and said directives to local public health units, letters to students in schools and a social media campaign were among the province's efforts to drive home the importance of measles vaccination.
"I hope today's terrible news really refocuses people with their primary care practitioners. If you have questions, please call Health 811," Jones said at an unrelated news conference on Thursday.
"Listen, this is real. This is impactful. And as we have seen this week, (measles) sometimes can lead to death."
Dr. Ninh Tran, medical officer of health at Southwestern Public Health, said the death is "devastating news for the community" and offered "heartfelt thoughts to the family."
"This event underscores the seriousness of measles in pregnant individuals, as it can cause low birth weight for the baby, preterm birth, and miscarriage," Tran said in a statement.
Immunocompromised people are especially vulnerable to severe complications from measles including pneumonia and brain swelling, he said.
Moore called death from measles "rare," but noted that measles "poses a serious risk" to people who have not been immunized with the measles, mumps and rubella vaccine.
A child under five years of age died of measles in Hamilton, Ont., in the spring of 2024. Before that, there had been no measles deaths in the province in more than a decade.
"I urge everyone, but especially those who may become pregnant, to ensure they have received two doses of the MMR vaccine, which will protect both a parent and baby," he said.
"This vaccine has been safely used for over 50 years and is highly effective. Two doses provide nearly 100 per cent protection."
News of the death came as Public Health Ontario released its latest measles case count.
As of Tuesday, there were 121 additional cases since the previous week, the agency's report said.
That pushed the total number of cases to 2,009 people — largely unimmunized infants, children and adolescents — infected with measles since last fall.
"The continued increase in the number of outbreak cases and geographic spread is predominantly due to ongoing exposures and transmission among individuals who have not been immunized," the Public Health Ontario report said.
It said 140 people have been admitted to hospital with measles during the outbreak, with nine of them requiring intensive care.
Southwestern Ontario has been hardest-hit with 725 cases, including 21 new cases since last week.
According to the most recent data available from the Public Health Agency of Canada, all provinces and territories except New Brunswick, Newfoundland and Labrador, Yukon and Nunavut have had measles cases this year.
Ontario and Alberta have had the most measles cases and the numbers continue to climb.
As of Wednesday, Alberta has had 749 measles cases, with 18 of them currently contagious.
–With files from Hannah Alberga
This report by The Canadian Press was first published June 5, 2025.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
Nicole Ireland, The Canadian Press
