Parents whose children attend the West End YMCA Daycare at 931 College St., learned over the weekend about the adult who had been at the daycare and the fact that their children may have been exposed to measles. The notification came via Toronto Public Health.
A parent told CBC News that the adult was at the daycare on two occasions during the week of Jan. 26.
Children are typically first vaccinated for measles at the age of 12 months, but are not vaccinated again until they are four to six years old. That suggests some children at the daycare may have only received a single vaccination to date.
Parents have been told a vaccination clinic will be set up at the daycare on Monday.
The YMCA directed inquiries from CBC News to Toronto Public Health.
Toronto Public Health would not comment specifically on the case at the West End Junior YMCA Daycare.
But Toronto Public Health did say that it follows up in cases of exposure in environments where individuals may not be fully immunized. These include health-care settings, schools and daycares.
Dr. Michael Gardam, an infectious disease specialist, said that anyone who has had a single vaccination and is then exposed to measles should get a second vaccination dose as quickly as possible.
Within 72 hours of exposure is the ideal window in which to receive a second vaccination.
But Gardam said a second vaccination will still have benefits should a person have a subsequent exposure to the virus.
Gardam said measles is highly contagious.
"Measles is one of the most contagious infectious diseases we know, so literally walking in the room, spending three minutes and picking up your child is enough to potentially infect the entire room. It would all depend on whether they actually have protective antibodies or not," Gardam told CBC News in an interview.
"So, it is really incredibly contagious and it's spread through the airborne route. So I don't have to touch you, or come even close to you — if you're breathing the air that I just exhaled, you can get infected."
Health officials have recently confirmed six cases of measles in Toronto — four adults and two children under the age of two.