Amid rumours of U.S. measles parties, experts warn how dangerous they can be

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 Tuesday, March 4, 2025.THE CANADIAN PRESS/ Geoff Robins

Following a warning from a U.S. official against “measles parties” amid outbreaks, dozens of Canadian health officials say they haven’t heard evidence of these dangerous events taking place above the border. Still, with case numbers that have already outpaced last year, doctors are warning anyone considering the idea not to do it.

Measles, a highly contagious virus preventable through vaccines, has been spreading through the U.S. in recent months, particularly in Texas and New Mexico, reports The Associated Press. Hundreds of cases have been confirmed in the two states alone and two people have died, one of whom was a child. Measles has also been reported in several other U.S. states.

In Canada, more measles cases were reported in the first two months of 2025 than in all of 2024, according to the country’s top doctor. Data published Friday showed Canada’s case count stands at 224.

The problem with measles parties

The theory behind these parties is that children are exposed, get sick and build immunity. The “parties” are parents or guardians bringing their otherwise healthy children to gatherings where they are intentionally in contact with a person who is known to have measles.

Late last month, a health official in one of the states hit hardest by the 2025 measles outbreaks addressed these parties specifically, saying parents don’t know how their children will handle the infection.

“We can’t predict who’s going to do poorly with measles, be hospitalized, potentially get pneumonia or encephalitis and/or pass away from this, so that’s a foolish idea to go have a measles party,” said Ron Cook of the Texas Tech University Health Sciences Center. Cook did not say how many, if any, of these parties have actually been held in the States.

It’s unclear whether infections in the States have stemmed from such events, and so far, it does not appear measles parties are popular in Canada.

Some Canadians on sites including Reddit and Facebook say they know of older family members who attended such parties decades ago, or remember “pox parties” – similar events meant to expose children to chicken pox.

CTVNews.ca reached out to dozens of clinics, hospitals and public health officials, and received responses denying any knowledge of measles parties but condemning any plans to hold them.

In an emailed statement, Dr. Sarah Khan in Hamilton, Ont., said she “emphatically discourages anyone from considering such a thing to infect their child.”

“Doing so would endanger their child’s health and the health of those around them,” the infectious disease specialist from McMaster Children’s Hospital said, echoing Cook’s concerns about serious complications “and even death.”

Dr. Azim Kasmani, medical officer of health in an area of Ontario that has seen recent cases, is another expert who hadn’t heard about any measles parties in the Niagara region. On the dangers of measles, he said it “can cause serious illness, with complications including pneumonia, deafness, brain inflammation, and, in severe cases, death.”

Their comments are in line with U.S.-based research conducted amid an outbreak in 2018-19 in New York. Researcher Dr. Wan Yang said these parties may have caused the “second, larger wave” of the outbreak. Modelling of the outbreak’s trajectory suggested the rate of the measles spread in a certain age group was unlikely without intentional contact with infected children, according to Yang.

2025 measles outbreaks

Measles, also known as rubeola, has been spreading through the U.S. and Canada in recent weeks, with hundreds of confirmed cases south of the border, and 173 confirmed in Canada as of the most recent data available (March 9).

Combined with 51 probable cases, the total for 2025 is now 224. There were 146 measles cases in Canada in all of 2024, and just 12 in 2023, according to federal data.

Case date from the last 25 years shows that Canada’s case count has spiked at times, including in 2014, when there were 418 cases by the end of the year, and in 2000, when there were 207. A particularly bad year, however, was in 2011, which saw a total of 751 cases, largely due to what’s described as the “largest epidemic in North America in a decade” by researchers. According to an article published in the Journal of Infectious Diseases the next year, 725 cases of measles were noted in the province in 2011, with adolescents making up more than half of the total number of patients.

Cases have been noted in several provinces, with outbreaks in areas including Ontario, Quebec, B.C. and Manitoba. An earlier outbreak in New Brunswick has been declared over.

The latest situation report from federal health officials shows Ontario and Quebec dealing with the most recent and highest number of cases.

The cases confirmed this year were in patients 54 and younger, with 42 per cent of patients falling in the 5 to 17 category. Health Canada says 82 per cent of people who are known to have had the infection were unvaccinated, and nearly eight-in-10 confirmed cases of measles have been in Ontario.

Public Health Ontario told CTVNews.ca in an email that it was not able to confirm whether measles parties have happened in the province, as they are not something that would be formally reported, but that all cases are “thoroughly investigated” to identify the likely source. In the past, most cases in the province have been tied to international travel, but the majority of cases in the most recent outbreak have been acquired within the province.

In many provinces, including Manitoba, exposure sites are posted publicly so those who may have been exposed can monitor themselves for symptoms.

The country’s top doctor, Theresa Tam, called this year’s increase in cases in Canada a “concerning trend,” and urged Canadians to check that their vaccinations are up to date, a message CTVNews.ca heard from many experts we contacted.

Measles symptoms

According to Health Canada, the symptoms of measles can include fever, cough, runny nose and red, watery eyes. It may then progress to include a rash that “looks like red spots and blotchy patches” that starts on the face then spreads across the body.

Complications include ear infection, pneumonia and diarrhea, and while rare, severe complications including respiratory failure, encephalitis (inflammation and swelling of the brain), and death are possible.

Encephalitis can lead to blindness, deafness and brain injury, among other possible conditions.

Those who are pregnant when they get measles may have a miscarriage or go into premature labour, Health Canada says.

While there is no specific treatment, those who think they may have measles are asked to isolate at home and call their doctor or other health-care provider, such as an urgent care or walk-in clinic, before attending in person, so precautions can be taken.

Who is most at risk?

In an interview last week, infectious disease expert and clinician Dr. Isaac Bogoch told CTV News Channel that those who are most vulnerable to measles are those who are unvaccinated or under-vaccinated, including children, and those who are immunocompromised.

Public Health Ontario said infants less than one year of age are in this high-risk category.

Bogoch warned that there’s a misconception that measles is a routine childhood illness “that everyone used to get decades ago, and everyone was fine,” he said. “This can have significant morbidity and even mortality associated with it, about 100,000 deaths per year, mostly in children around the world.”

Can I get measles if I get vaccinated?

Public health officials say staying up to date on immunizations is the best way to protect yourself and children. The measles vaccine is two doses, typically given to children in Canada as part of a vaccine known as MMR (measles-mumps-rubella) or MMRV (measles-mumps-rubella-varicella). The first dose is often given to children between the ages of 12 and 15 months, then a second dose when children are between the ages of four and six.

Health Canada says the efficacy of a single dose of the MMR or MMRV vaccine, if given on the usual schedule, is between 80 and 95 per cent, with a second dose bringing that to “almost 100%.”

A breakdown of 2025 measles cases shows nearly all were in patients who’d never had the vaccine, while 4 per cent were in those who’d had one dose, and 10 per cent in those with two or more doses. Health Canada did not give further information on those statistics, including whether those who were fully vaccinated had both doses as children or adults.

Health officials say Canadian adults born before 1970 are “generally presumed to have acquired natural immunity,” but that some are still at risk.

The U.S. Centers for Disease Control estimates that about three per cent of people who’ve been fully vaccinated will still get measles if exposed, but says they’re less likely to pass it on to others, and more likely to have a “milder illness.”

How do you contract measles?

Measles is considered very contagious.

Like many viruses, measles is spread through exposure to a person who has an infection. This can be through touching contaminated surfaces or breathing in the air after a person coughs or sneezes (even if they’ve left the room up to two hours before), the U.S. CDC says. It can also spread through “direct contact with secretions … from the nose and throat of someone who’s infected,” Health Canada says, listing mucus as an example.

With files from CNN, The Associated Press and CTV News Channel