Ontario is grappling with a significant measles outbreak, reaching its highest levels in a decade. As of March 12, 2024, the province has reported 252 confirmed and 66 probable cases of measles, totalling 350 cases in the first three months of the year. This marks a sharp rise from previous years, with 173 new cases reported in just the last month since February 27.
The outbreak, which started with a travel-related case in New Brunswick on October 18, 2024, has spread to both Ontario and Manitoba. Public Health Ontario (PHO) attributes the surge in cases to the unvaccinated population. The report reveals that 74% of the affected individuals are children and adolescents, while 24.9% are adults. Alarmingly, seven pregnant women have contracted the disease, with five being unvaccinated and two having received two doses of the measles, mumps, rubella (MMR) vaccine. Additionally, a newborn has been infected.
Dr. Isaac Bogoch, an infectious disease expert, emphasized the highly contagious nature of measles and stressed the importance of maintaining a vaccination rate of 95% or higher to prevent further spread. “Measles tends to spread rapidly in areas with low vaccination rates,” Dr. Bogoch warned, urging communities to be vigilant.
The outbreak has affected 11 public health regions across Ontario, with the Southwestern region being the most heavily impacted. As of the latest data, 181 cases (51%) have been reported in the Southwestern Public Health Region, which includes Oxford, Elgin counties, and the city of St. Thomas. Despite the surge, Toronto has seen a relatively stable situation, with only two confirmed cases this year. However, experts caution that areas within the Greater Toronto Area (GTA) could still be at risk, particularly in regions with lower vaccination rates. Dr. Bogoch warned that crowded public spaces such as shopping malls, public transportation, and airports could facilitate the spread of the virus.
The rise in measles cases this year is stark compared to previous years. Between 2013 and 2023, Ontario recorded only 101 confirmed measles cases, with an average of just seven to 22 cases annually. There was even a significant drop during the COVID-19 pandemic, with only one case recorded from 2020 to 2022. However, in 2023, the number of cases spiked to seven, and in 2024, that number has surged to 64, with health officials concerned that the first quarter of 2025 could see more than three times the number of measles cases recorded in the entire 10 years from 2013 to 2023.
Experts and health officials agree that the most effective way to stop the spread of measles is through vaccination. The MMR vaccine, which has been in use for over 50 years, is one of the safest and most effective vaccines available, offering nearly 100% protection after two doses. The vaccine is typically administered in two doses: the first at 12 months of age and the second between ages four and six. Even the first dose is more than 95% effective in preventing the disease.
Ontario’s Chief Medical Officer of Health, Dr. Kieran Moore, strongly urged Ontarians to ensure they and their children are up to date with their immunizations to curb the outbreak. Health officials are also working to increase vaccination rates, especially in communities where immunization rates are low, to prevent further spread of the disease.
In response to the surge, public health campaigns are being ramped up, and efforts will focus on vaccinating vulnerable and unvaccinated populations. Individuals are encouraged to check their vaccination status and get vaccinated if necessary.