Canada's chief public health officer Dr. Theresa Tam is doubling down on warnings to young Canadians to stop fuelling the spread of the novel coronavirus.

Tam says that age group accounted for the highest incidence rates for COVID-19 cases in the past two weeks.

"I must urge all Canadians, particularly younger adults, to not give in to COVID-19 fatigue," she said Friday in Ottawa.

"This is your generation and your future that is being shaped. Younger age groups are not invincible against COVID-19," said Tam, who returned to the government's public briefings after her own summer break.

Chief public health officer Dr. Theresa Tam is warning young people to wear masks and maintain physical distancing this weekend.

People in the 20 to 39 age group are to blame for rising COVID-19 infections in the past two weeks.

Alberta's chief medical officer of health says ballooning COVID-19 numbers there should be a wake-up call for those who are no longer practising physical distancing.

BC is about to clamp down and impose more restrictions in light of a surge in its numbers of infections.