OTTAWA -- One of Canada's top doctors is urging Canadians to keep following public health measures as cases of COVID-19 among young people continue to tick upwards — and he warns that if they don't, the country could face a potential "backslide."

"I think Canadians have made tremendous sacrifices and we've succeeded overall in flattening the curve, but that success is fragile and it only takes a few sparks and so on to backslide and create…the situation we don't want," said Deputy Chief Public Health Officer Dr. Howard Njoo at a press conference on Tuesday.

His comments come as COVID-19 cases trend upwards in Canada, especially among young people, with many cases linked to bars, restaurants and private parties.

In Kelowna, B.C., eight people tested positive for COVID-19 on Friday in connection with two private Canada Day parties. In Ontario, which reported its highest daily surge of new cases since June, more than half of the new cases were among those under the age of 39. And in Quebec, many cases among young adults have been linked to Montreal bars and private parties.

Njoo explained that while Canada averaged a daily COVID-19 case count of 300 in early July, that rose to an average of 350 per day over the last week — and in the last four days, there have been around "450, 460 cases per day," he said.

"We're concerned and we’re monitoring closely in terms of, hopefully, it's just a temporary blip. But we will obviously have to see what happens in the days and weeks to follow in terms of following the number of cases among young adults," Njoo said.

He noted that local health authorities have indicated to him that if certain venues, such as bars and restaurants, continue to be associated with transmission, "they're prepared to make adjustments as necessary."

Restaurants and bars have reopened in recent weeks across almost all of Canada, though owners are required to follow strict distancing guidelines. However, while bars in places like Montreal, Ottawa and Vancouver are open for business, some cities, including Toronto, have yet to receive the green light for customers to dine indoors. In the meantime, many are offering patio service.

Njoo attributed the uptick in cases among young adults to three factors. The first, he said, is a fatigue setting in after being cooped up all winter and with the advent of warm, sunny weather. The second is what Njoo called "the invincibility factor."

"I think at a certain age you think you can get away with anything, that you're basically able to deal with anything that comes and there won't really be any major consequences," Njoo said.

He noted that this message is a "tough one" to counter, because COVID-19 symptoms are by and large less severe among younger people. Out of Canada's 8,860 deaths linked to COVID-19, only 25 deaths involved individuals 39 or younger, according to Public Health data. However, Njoo warned that this doesn't mean young people are immune from passing the virus along to people they encounter who are at higher risk.

"They're part of our society, so they go to work, they obviously have older parents and grandparents, and certainly there's a risk of transmitting the virus to those who actually would be higher risk of severe consequences," Njoo said.

The third factor is what Njoo referred to as "the new normal factor." He speculated that some young adults, as they see bars and restaurants begin to reopen, assume they can "let go" and then have indoor parties without social distancing.

"I think across the country we need to redouble our efforts in terms of reaching all Canadians, including young folks," Njoo said.

Ontario Premier Doug Ford echoed Njoo's message Tuesday, imploring people to continue to take public health measures seriously and not go to parties.

"I just ask people, just hold off on these parties. I don't know why everyone wants to party so badly, but, enough," he said.

"Just don’t go to a party, simple."

B.C.'s Provincial Health Officer Dr. Bonnie Henry also issued a warning to her province on Monday, cautioning that the latest modelling projections show the province is "starting to see an upward bend of our curve."

"What this shows is that we do have a possibility of having explosive growth in our outbreak here in B.C. if we're not careful in how we progress over the summer," she said.

She directly tied the upward trend to private parties, bars and clubs.

"The challenge now is we're no longer having safe connections, and that is what is spreading this virus," Henry said.

"We're seeing parties, small groups of people going together to restaurants and bars and clubs but also in houseboats, in resorts, at private homes. And the challenge with that is we may not know those people we're in close contact with."

However, when asked on Tuesday if bars and restaurants should simply be shut down, Njoo explained that the answer to that is "complex," as it requires a balance of the public health measures with the unintended consequences they have — on mental health, non-COVID-19 related public health and the economy.

"The tricky part, really, is trying to find that balance as we slowly as a society figure out how we move forward with an appropriate amount of caution in terms of various sectors, in this case, the hospitality industry, bars and restaurants," Njoo said.

He explained that lessons learned throughout the pandemic, including with respect to the use of masks, have expanded the tools available to public health officials to lower the risk of transmission and to move forward, cautiously, with reopenings. However, he said Canadians should not let up when it comes to following public health guidelines.

"It only takes a few sparks and people letting go and not keeping their foot on the gas, so to speak, [and] we could backslide and unfortunately return to situations we had several months ago," Njoo warned.

With files from CTV News Vancouver's Andrew Weichel