Surge in Ontario measles cases renewing concerns about vaccination and risk of community spread

Ontario is facing its largest measles outbreak in nearly 30 years, with cases nearly doubling in two weeks, renewing concerns about vaccination rates and the risk of community spread.

Public Health Ontario says 78 new measles cases have been identified, bringing the total this year to just over 140, far surpassing the 101 total infections recorded in the province between 2013 and 2023. The last time there was a sizable outbreak in the province was 2008, when there was a total of 58 cases.

Measles is a highly contagious virus that spreads through the air when an infected person coughs or sneezes. Symptoms include fever, cough, runny nose and a red rash.

“The problem is a fever and a rash isn’t super concerning, but what can manifest afterwards, like the secondary bacterial infections, things like pneumonia, ear infections, and severe encephalitis, sort of a brain infection, that’s where we really see a lot of the severe disease that needs hospitalization and unfortunately can lead to death,” said Dr. Sarah Khan, Pediatric Infectious Disease Specialist at McMaster Children’s Hospital.

Almost all of the new cases are connected to an interprovincial outbreak that began in October, which has sickened 177 people in Ontario and also saw the virus spread in New Brunswick and Manitoba.

“These are outbreaks, in Texas and in Ontario, that are being fueled almost entirely by people who didn’t bother getting vaccinated against measles,” adds Dr. Dale Kalina, an Infectious Disease Specialist with the Brant Community Healthcare System. “It is an exceptionally, exceptionally contagious disease that, as we’ve seen in the outbreak in Texas, has led to a child dying. And it’s a disease that is easily preventable.”

The epicentre of Ontario’s outbreak has been in the Southwestern and Grand Erie public health regions. As a result, 18 kids have been hospitalized in Ontario, including one who required intensive care. Toronto Public Health has confirmed one case of measles, while York Region Public Health reported its second case of measles on February 28.

“The issue with trying to contain this is it’s one of the most infectious viruses. Essentially, if you’re in the same room or airspace as someone who’s infectious and you’re not immune, you have a 90 per cent chance of contracting this infection,” says Dr. Khan.

Those most at risk are small children, pregnant women and those with weakened immune systems. With March Break around the corner, airports and planes are opportune places for the virus to spread, and health officials say vaccination is the best path of protection.

“The vaccine is highly effective, it’s highly safe and effective against getting infected if you are exposed. And again, it’s that two dose that gives you really high levels of protection,” said Dr. Cheryl Young, the Associate Medical Officer of Health for York Region.

Canada eliminated measles in 1998, which required a low level of transmission for at least a year and 90 to 95 per cent vaccination coverage. But it risks losing that elimination status if the present outbreaks continue.