Ontario, Canada measles outbreak: Why is virus spreading in North America?

A serious outbreak of measles in Ontario, Canada, has added to concerns that the disease is rapidly spreading across North America.

The United States and Canada have been experiencing one of the worst measles outbreaks in years for the past few months, while the virus has also crossed to neighbouring Mexico.Thousands of cases and several deaths have been reported in outbreaks across the three countries. The World Health Organization (WHO) has warned that the “overall risk of measles in the Americas Region is considered high”.

The WHO said low vaccination rates are to blame.

Here is what we know about the outbreaks and why measles cases are rising.

How bad is the outbreak in Canada?
At least 2,009 cases of measles have been recorded in Ontario since October last year. A further 761 have been reported in Alberta.

In May, Canadian officials confirmed that the outbreak had originated from a large gathering in New Brunswick province that involved Mennonite communities, which strive for a simple life and tend to avoid modern technology and medicine.Three-quarters of new cases are in unvaccinated children, according to Public Health Ontario.

One baby who was born prematurely with a measles infection has died, Dr Kieran Moore, the chief medical officer for Ontario confirmed on Thursday, June 6.

In a statement, Moore said: “The infant contracted the virus before birth from their mother, who had not received the measles, mumps and rubella (MMR) vaccine. 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.”Nearly 40 percent of the cases in Ontario have been reported by the Southwestern Public Health Unit, which serves Oxford and Elgin counties and the city of St Thomas, southwest of Toronto.

Canada achieved “measles elimination status” in 1998, meaning there was no continuous spread of the disease for more than a year at that time. This year, however, more cases of the virus have been reported than during all of the 27 years since then.

Where is measles spreading in the US and Mexico?
At least four people have died from measles in Mexico this year, and three have died in the US; two children in Texas and one adult in New Mexico. All three were unvaccinated.

A WHO report in April stated that measles cases in the Americas during the first three months of this year were 11 times higher than during the same period in 2024. The region now faces a “high” risk of measles outbreaks, compared with a “moderate” risk globally, the WHO said.United States
In the US, an outbreak in West Texas is responsible for 80 percent of the 1,168 cases of measles reported this year so far, including 122 this week, according to government data. Most cases this year have been in Texas, New Mexico and Oklahoma.

This is the second-highest number of cases in the US since the country achieved “measles elimination status” in 2000.

In response to the Ontario outbreak, public health officials in New York state issued a warning to residents to get vaccinated against measles before travelling to the Canadian province.

“Measles is only a car ride away!” the New York State Department of Health wrote in its April 2 travel advisory. “Currently, measles outbreaks are happening in parts of the United States and Canada, especially in Ontario, and around the world.”

In 2019, the US experienced its most significant measles outbreak since 1992, with 1,274 confirmed cases reported across 31 states, but no deaths.

Mexico
Mexico had reported 1,520 measles cases as of late May, according to data from the Pan American Health Organization. The cases are concentrated in the northern state of Chihuahua.

Just seven cases were reported in the whole of Mexico last year. A 31-year-old unvaccinated man from Ascension, Chihuahua, died from the disease in early April this year and at least three more deaths have been reported since then.

In April, Mexico issued a warning for people travelling to the US and Canada due to high measles case rates.

What is measles?
Measles is a highly contagious viral illness that starts with symptoms including high fever, cough, runny nose, red or watery eyes, and sensitivity to light. A few days after infection, a red, blotchy rash typically appears on the face and spreads down the body. Fatigue and loss of appetite are also common.