Toronto Public Health has confirmed it is now investigating five confirmed cases of measles involving two children under the age of two, and three adults from different families.
The public health agency said it is probing the potential links between the cases, but says there is no confirmed connections between them.
"This indicates measles is currently circulating in Toronto," TPH said in an email statement to CTV Toronto Thursday afternoon.
Earlier this week, the city confirmed it was investigating four confirmed cases of measles. The latest case was identified in the third adult.
Infectious disease specialist Dr. Neil Rau previously told CTV News Channel that the infected individuals likely came into contact with someone carrying measles, and may not have realized it. He adds that that carrier likely came to Canada from abroad.
Measles is common in many parts of the world, including India, sub-Saharan Africa, the Philippines, and South America, Rau said on Monday.
"When people from those countries arrive here, they won’t necessarily have symptoms, they’ll be incubating the disease, and they can be contagious for days before coming out with the rash," he said.
"Then they become contagious, get a rash and get over it, but they can spread it to many people in the process if they don’t have immunity."
While many Canadians have received the measles vaccine, there is growing concern that the younger population may be at risk. In Ontario, the number of students enrolled in school that have been immunized seems to be shrinking. Approximately 96 per cent of 17-year-olds in Ontario have been vaccinated against the measles, compared to 88 per cent of seven-year-olds.
Measles is a highly contagious disease that spreads easily in the air. There is no specific treatment for the disease. While most people fully recover, in rare cases, measles can lead to encephalitis (brain inflammation) and death.
