Dr. Asmaa Hussain, a pediatrician in southwestern Ontario, was among the first physicians in the province to admit a child with measles to hospital at the start of the current months-long outbreak.
It was in November, and the young child was severely dehydrated, had difficulty breathing and had developed the unmistakable full-body rash. The child had an underlying medical condition, making them more vulnerable to severe infection.
Hussain, who went to medical school in Iraq, had seen measles patients in that country, but never in her 17 years treating children in Ontario. Though she recognized the symptoms, Hussain was surprised to see a child with the extremely infectious disease in her small community hospital.
“This case was at the beginning of the outbreak, and it was, like, ‘How can this be?’ ” said Hussain, chief of pediatrics at St. Thomas Elgin General Hospital, about 30 kilometres south of London. “Because measles should not be here.”
Over the next few months, southwestern Ontario would become the epicentre of a measles outbreak, now the largest in Canada in more than 30 years.
On Thursday, Ontario reported more than 1,000 measles cases linked to the outbreak. The ongoing spread — about 100 new cases are being added to the provincial tally each week — has prompted public health officials to warn that Canada is at risk of losing its elimination status for measles, which the country has maintained since 1998.
Experts are urging people to check that their immunizations are up to date, to ensure they are protected and to prevent measles from further spreading in the province. Public health data shows the majority of people sickened in the outbreak — 75 per cent — have been infants, children and teens, most of whom were unvaccinated.
“Here we are, facing a disease we thought we had eliminated,” said Dr. Sarah Khan, an infectious disease specialist at McMaster Children’s Hospital in Hamilton. “It’s really disheartening, really disappointing. We have a highly effective, safe vaccine and despite that, there’s such a degree of hesitation and misinformation. It’s resulting in real harm.”
The outbreak, which started in mid-October after an infected traveller from New Brunswick arrived in the province, has since spread to 15 public health units, primarily in southwestern Ontario. Public health officials have confirmed the outbreak is concentrated in communities with low immunization rates, including Mennonite and Amish communities.
As of April 23, the outbreak has led to at least 1,020 measles cases — an increase of 95 cases over the previous week, according to . The number of people who have been hospitalized with the disease now sits at 76, including seven who needed intensive care. Of those who required hospital care, 72 were unimmunized, including 57 children.
Shelly Bolotin, director of the Centre for Vaccine Preventable Diseases at the University of Toronto, noted that about one in four cases in the current outbreak are children under five, “who are at increased risk from complications like pneumonia, ear infections and even swelling of the brain.”
“Since the measles virus infects immune cells, it affects long-term immunity, too, so these (and all) cases will also be at higher risk for other infections for the next several years,” Bolotin said.
Khan, associate medical director of infection prevention and control at Hamilton Health Sciences, said the vast majority of people sick enough to need hospital care are young children and those who are immunocompromised or pregnant.
Khan said she recently cared for an unvaccinated child in hospital with measles who was “very sick and needed a lot of oxygen support.” Though she stressed the importance of immunization with the child’s parents, Khan said they were not receptive.
“Their child was going to make a recovery and that’s all the parents were willing to speak about,” she said, noting she had not seen a measles case in her medical career until this past year. Last May, an unvaccinated child in Hamilton died, the first measles death in Ontario in more than a decade.
pc28Public Health has reported three cases, including one Thursday, that are not associated with the ongoing outbreak. In 2025, there have been at least 35 measles cases in the province that are not outbreak-linked, according to Public Health Ontario. Six of these patients, all of whom were unvaccinated children and teens, have been hospitalized.
Since November, Hussain’s hospital has cared for 14 people admitted with measles. Most were unvaccinated toddlers and very young children, some needing oxygen to help with their breathing, others needing supportive measures, such as IV fluids. One patient was pregnant. Like other viral illnesses, there is no specific treatment for measles, Hussain said.
She said parents at her hospital were worried about their children, but many remained unconvinced of the importance of immunization. However, she added, other families, whose unvaccinated children had not yet been infected, have come to the pediatrician’s office and asked for immunizations.
“They have seen neighbours and friends with measles, and got worried for their children.”
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