Montreal public health officials say someone contagious with the measles virus who was not vaccinated attended an NHL game at the Bell Centre on March 3 between the Canadiens and the Buffalo Sabres.
Officials say people are considered measles contacts if they were a spectator or concession worker in the red area of seats in sections 111 to 117 between 5:30 p.m. to midnight.
Workers at the Tim Hortons and Pizza Pizza inside the arena are also considered measles contacts.
Health officials are recommending that anyone considered a contact who is unvaccinated against the disease should isolate at home until March 17 inclusive.
People outside the measles risk area could have been exposed to the virus but are not considered contacts and are advised to monitor for symptoms.
There have been 31 confirmed cases of measles in Quebec between mid-December and March 7, with 24 cases in the Laurentians region north of Montreal.
