Ontario measles cases rise amid growing concern about spread among unvaccinated individuals
Measles cases continue to rise in the country's most populous province, with Public Health Ontario reporting Thursday there has been more than 100 new cases of the highly contagious disease in the last week.
New figures released by Public Health Ontario 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 new 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 spread of measles is a growing concern in Canada, which stands in stark contrast to the country's status in 1998, when the disease was deemed to be eliminated. Public health specialists credit the measles, mumps, rubella vaccine for preventing spread of the disease in the last the decades.
But they are increasingly worried about what is unfolding: Ontario now has the highest number of cases it has seen in more than a decade. There have also been recent cases in New Brunswick, Quebec and Alberta. Additionally, there is a global resurgence of measles, such as in Europe. There have also been outbreaks in the U.S. in New Mexico and rural parts of Texas.
Health officials highlight accelerated MMR vaccine guidance in measles outbreak areas of Ontario
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.
Since last October, a total of 470 measles cases (361 confirmed and 109 probable) have been reported. The cases are associated with an outbreak that has occurred in 11 public health units. Last October, a travel-related case in New Brunswick led to measles cases in Ontario.
Ontario's Chief Medical Officer of Health, Kieran Moore, said last week that the majority of cases in the province are among unvaccinated individuals.
Dr. Moore 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 near Hamilton and London respectively. Both are seeing measles outbreaks.
He advises that babies aged six to 11 months should receive one dose of the MMR vaccine and two additional doses are still recommended after turning one. Children who are aged one to four who have received a dose of the measles vaccine should receive a second dose as soon as possible and at least four weeks after the first shot. Infants under six months are too young to receive a dose.
Measles is re-emerging in Ontario. Here's what you need to know to protect you and your family
Dr. Moore also said adults born in 1970 or later are encouraged to ensure they have received a second MMR shot. An immunization program for infants was introduced in 1983 when a single dose was given at one year of age. Public Health Ontario said a second dose was added in 1996.
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 Ontario said that measles cases in the province has been rare, owing to the successful elimination of measles in Canada in 1998 and high vaccination coverage.
It said the sharp increase in the number of outbreak cases and the geographic spread in recent weeks is because of 'continued exposures and transmission among individuals who have not been immunized.'
Measles is a highly contagious, airborne disease. It can result in serious health complications that, while rare, include respiratory failure, encephalitis, which is swelling of the brain, and death.
Symptoms for the disease include fever, cough, runny nose, red and watery eyes, and a rash that appears like red spots or blotchy patches. It can result in serious health complications that, while rare, include respiratory failure, encephalitis and death.
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What we know about measles during pregnancy
The death of an Ontario infant (new window) born prematurely and infected with measles through the mother is raising questions about how the virus is transmitted during pregnancy. On Thursday, Ontario health officials announced the death of a baby (new window) who was infected with the virus while in the womb. It was the first fatality in the provincial outbreak that began on Oct. 28 last year and includes 2,009 probable and confirmed cases. 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, Dr. Kieran Moore, Ontario's chief medical officer of health, said in a statement released Thursday. Measles is a respiratory infection with symptoms that include fever, a blotchy rash, a cough and red, watery eyes. In May 2024, a child under five died of measles in Hamilton (new window) , but before that, there were no measles deaths in the province in more than a decade. Measles-infected baby dies in southwestern Ontario (new window) Moore has previously said the current outbreak was traced to a Mennonite wedding in New Brunswick, and is spreading primarily in Mennonite and Amish communities where vaccination rates lag. The majority of those cases are in southwestern Ontario. WATCH | Death of a measles-infected baby in Ontario: Début du widget Widget. Passer le widget ? Fin du widget Widget. Retourner au début du widget ? Measles-infected baby dies in southwestern Ontario An infant born prematurely and infected with measles in the womb through their mother has died, Ontario's Chief Medical Officer Dr. Kieran Moore announced Thursday. It is the province's first recorded death from the current outbreak that started in October of last year. Health officials stress that anyone who isn't vaccinated is vulnerable to measles and they encourage everyone to ensure they are up to date on their Measles, Mumps and Rubella (MMR) vaccines. 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It is almost always fatal and generally develops seven to 10 years after an initial measles infection (new window) , even if the person appears to have fully recovered. It can be dormant in the brain for years and may eventually flare up, causing brain inflammation and resulting in children or young adults losing the ability to move and speak. According to the Public Health Agency of Canada, SSPE occurs in between four and 11 out of every 100,000 measles cases. Health officials say it strikes between seven and 11 years after an initial infection and the highest rates are among children who contract measles before the age of two. If I'm pregnant can I get the measles vaccine? No, the measles vaccine is not recommended to be administered to people who are already pregnant. If you want to take the measles vaccine, it has to be before you're pregnant, Choo said. That's because the measles vaccine contains a live strain that is a weakened form of the virus, which is not recommended during pregnancy. Choo says that's because there is a theoretical risk that the measles virus contained in the vaccine can be passed to the baby. In contrast, vaccines that contain inactivated viruses can be given during pregnancy. The flu vaccine is one example. Is there treatment for pregnant people exposed to measles? If you're pregnant and you think you may have been exposed to measles, health officials advise you to contact your local health authority. They can determine if exposure occurred and direct patients to seek appropriate care without contributing to further spread. If measles exposure is confirmed, Choo says there is an injectable medication option called IVIg (new window) . Depending on when the exposure occurred, the medication may be used to help protect against infection or reduce severity of the illness. However, health officials and doctors agree that the best way to protect against measles is immunization. The most important recommendation or advice I can give … is to make sure you're up to date with all the immunization if you're starting that journey of becoming pregnant, Wong said. CBC News with files from CBC's Alison Northcott and Christine Birak
