A dose of the measles, mumps, and rubella (MMR) vaccination awaits the next patient during a vaccine clinic at Southwestern Public Health in St. Thomas, Ont., on March 4.Geoff Robins/The Canadian Press
Ontario has reported more than 100 new cases of measles in the last week alone, sparking further concern about the spread of the highly contagious disease in the country’s most populous province and how it can result in serious complications and even death.
New figures released by Public Health Ontario on Thursday show since the beginning of 2025, a total of 440 measles cases (357 confirmed and 83 probable) have been reported in Ontario, as of this Wednesday.
The figures represent an increase of 120 cases (103 confirmed and 17 probable) since the release of its epidemiological summary last week which noted nearly 200 cases.
“The sharp increase in the number of outbreak cases and the geographic spread in recent weeks is due to continued exposures and transmission among individuals who have not been immunized,” the report said.
The spread of measles is a growing public-health concern in Canada – a stark contrast to the country’s status in 1998 when the disease was deemed to be eliminated. In past decades, the measles, mumps, rubella vaccine is credited for preventing its spread and saving lives.
But health officials in Canada are increasingly worried about the spread of the disease. At a briefing on Thursday, Ninh Tran, the Medical Officer of Health for Southwestern Ontario, issued a plea amid an outbreak. “If this vaccine did not work, we would have a very different case count,” Dr. Tran said. “Please, do not risk your health or your child’s health through a measles infection.”
Ontario now has the highest number of cases it has seen in more than a decade, according to its Chief Medical Officer of Health Dr. Kieran Moore. Elsewhere in Canada, there have been recent measles cases in New Brunswick, Quebec and Alberta.
There is a global resurgence of the disease, including in Europe. In the U.S., there have been outbreaks in New Mexico and West Texas, where there have been nearly 320 cases. A school-aged child died after contracting measles in West Texas last month, and New Mexico reported its first measles-related death involving an adult last week.
Cases have also been reported in several other states. State department health officials in Oklahoma reported two probable cases last week, and said they were associated with outbreaks in West Texas and New Mexico.
By comparison, Public Health Ontario said that between 2013 and 2023, 94 cases occurred in individuals born after 1970. It said 28 cases resulted in hospitalization but that there were no deaths. In 2024, it reported there were 64 cases in individuals born after 1970, and eight cases involved hospitalization. A child under five who was not vaccinated died.
Adults born before 1970 are presumed to have acquired immunity to measles. Public health officials say individuals born after that time should check to see if they received one dose or two. A sole dose was given as part of a widespread immunization program for infants introduced in 1983; a second dose was added in 1996.
Canada’s Chief Public Health Officer, Theresa Tam, has said the majority of measles cases reported domestically are among unvaccinated people, many of whom are children and infants.
Dr. Moore said last week that the majority of cases in the province are among unvaccinated individuals. He recently issued a memo with new immunization recommendations that apply to individuals who live, work, travel, worship or spend time in the areas covered by the Grand Erie and Southwestern public health agencies. Both are seeing measles outbreaks.
His advice includes adults born in or after 1970 ensure they’ve had the second MMR shot. Additionally, he recommends babies aged six to 11 months receive one dose of the MMR vaccine and two additional shots are still recommended after age one.
Children one to four years who have received a dose of the measles vaccine are encouraged to receive a second dose as soon as possible and at least four weeks after the first shot. Infants under six months cannot receive a dose.
Data indicate childhood vaccination coverage in Canada is sliding. A recent study published in the Canadian Journal of Public Health found a decline in measles vaccination coverage in children in 2023 compared with 2019.
Public-health specialists attribute the routine vaccination decline to a number of factors including that many lack access to primary health care providers, paused immunization programs during the COVID-19 pandemic and medical misinformation.
Measles is a highly contagious, airborne disease. Symptoms include fever, cough, runny nose, red and watery eyes, and a rash. Serious health complications, while rare, include respiratory failure, encephalitis and death. For pregnant people, it can cause low birth weight for the baby, pre-term birth and miscarriage, Dr. Tran said.
With reports from the Associated Press