Seventeen cases of measles have been confirmed in Quebec, Ontario, Saskatchewan and British Columbia — more than half of those in the Montreal area, while one Ontario case has been linked to a high school.

Quebec public health director Dr. Luc Boileau confirmed 10 cases on Monday, almost all of them involving children and making Montreal the country’s epicentre. He said only three of the cases were linked to travel outside of the country, indicating community spread in and around the city.

Public Health Ontario confirmed five cases of measles and said all but one involved travel.

The latest case, announced last week, was in a man in his 30s in the York Region north of Toronto and was “likely” related to community transmission, the region’s medical health officer said.

The man had “close contacts” among students and teachers at a high school so public health officials in that region are ensuring everyone there is vaccinated, Dr. Barry Pakes said.