Ontario declares measles outbreak over after nearly a year of spread

TORONTO – Ontario’s measles outbreak, which sickened more than 2,300 people over the course of nearly a year, highlighted the consequences of declining vaccination rates and led to the death of a newborn, has been declared over.

Public Health Ontario and the province’s top doctor said Thursday the outbreak ended on Monday because it had been 46 days since any new reported cases — twice the maximum incubation period for measles.

“In Ontario, the last confirmed case developed a rash on August 21, 2025, following several months of steadily declining case numbers,” Dr. Kieran Moore, the province’s chief medical officer of health, said in an emailed statement.

“We have now surpassed the required threshold with no additional cases identified.”

The spread, which infected 2,375 people in Ontario spanning 26 local public health units, started on Oct. 18 last year after exposure to someone who had measles in New Brunswick.

New Brunswick declared its outbreak over in January.

Almost three-quarters of the people infected with measles in Ontario have been infants, children and adolescents. More than 96 per cent of them were unvaccinated.

During Ontario’s outbreak, a baby in the province’s southwest was infected with measles in the womb and died after the mother, who was unvaccinated, gave birth prematurely, the province announced in June.

Alberta, which has been in the midst of a measles outbreak since March, announced the death of a baby earlier this month. The infant was also born prematurely after the mother contracted measles while pregnant.

As of Thursday, 1,925 measles cases have been reported in Alberta.

Measles was declared eliminated in Canada in 1998, but the country may lose that status on Oct. 27. Elimination status is revoked after 12 months of continuous transmission.

There have been 43 additional cases of measles in Ontario this year that weren’t linked to the outbreak, according a Public Health Ontario report released Thursday. Three of those people were infected in September.

The Public Health Agency of Canada’s website shows that although the majority of measles cases in 2025 have been in Ontario and Alberta, infections have also been reported in every province. One case was reported in the Northwest Territories. No cases have been reported in Yukon or Nunavut.

Moore cautioned that although the end of the outbreak “marks an important milestone,” measles is a “serious and highly contagious disease” and urged everyone to ensure their measles, mumps and rubella (MMR) vaccinations are up to date.

“Two doses of the MMR vaccine offer nearly 100 per cent protection and have been safely used for decades,” he said.

This report by The Canadian Press was first published Oct. 9, 2025.

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.