If cases of COVID-19 continue to multiply, labour shortages could affect food supplies and undermine Canada's critical infrastructure, an internal government briefing note obtained by CBC News warns.

The document, prepared by Public Safety Canada, says accelerating rates of illness among Canadians could create labour shortages in essential services.

The two most "pressing" areas of concern, it says, are procurement of medical goods and the stability of the food supply chain.

"These shortages are likely to have the greatest impact in the two sectors mentioned above, as it will affect our ability to provide health care and essential goods, including food, to Canadians," notes the document.

"Labour shortages could also affect Canada's critical infrastructure, including power grids, banking and telecommunications and this will further impair Canadians' quality of life at this difficult time."

A federal source, speaking on the condition they not be named, said there's a fear that some workers in essential services, including prison guards, will refuse to come to work for safety reasons.

Canadian Labour Congress president Hassan Yussuff said workers have the right to refuse work if they feel unsafe, although the only resistance he's seeing on a national scale so far is happening among long-term care workers who don't have proper safety gear.

He said securing more personal protective equipment could calm fears across a number of sectors.

"I know this is a learning curve. You wouldn't have thought, and I wouldn't have thought, that grocery clerks should have personal protective equipment like a mask, or a bus driver," Yussuff said.

"We have never encountered seeing people in those types of jobs wearing a mask doing their regular duties but because of COVID-19, I think we have to be far more vigilant and I think those workers have every right to request the proper mask and their employer should be able to provide it.

"I know everybody is scrambling to make sure that is the reality. But of course, with the limited availability of products, I'm hoping by a week or two maybe most of this might be solved."

Food supply concerns grow

Fears about the stability of supply chains are already playing out in parts of the country.

Oceanex Inc., one of Newfoundland and Labrador's largest shipping companies, said Monday that it might have to cancel shipments due to pandemic-related financial losses.

A day later, Marine Atlantic, a federal agency, said it can step in if Oceanex Inc. has to stop carrying freight to St. John's.

"We're looking at all options just to make sure the supply chain stays in place," Seamus O'Regan, MP for St. John's South-Mount Pearl, said Tuesday. "It's way too important so we'll make sure it gets done."

The Cargill meat packing plant in southern Alberta temporarily laid off 1,000 workers after dozens at the plant tested positive for COVID-19, according to the union. (Google Maps)

In Alberta, the union representing some workers at the Cargill meat packing plant in High River, about 60 kilometres south of Calgary, is arguing the facility should be closed for at least two weeks to come up with a plan after 38 workers there tested positive for COVID-19.

It echoes a story playing out in the U.S., where the head of Smithfield Foods Inc. — the world's largest pork producer — recently warned that American meat supplies are "perilously close to the edge" after it shut its South Dakota plant due to an outbreak.

"The closure of this facility, combined with a growing list of other protein plants that have shuttered across our industry, is pushing our country perilously close to the edge in terms of our meat supply," said Smithfield's chief executive officer Ken Sullivan in a statement.

"It is impossible to keep our grocery stores stocked if our plants are not running."

In a briefing on Wednesday, Agriculture Minister Marie-Claude Bibeau says she's confident Canada has enough food but acknowledged labour shortages on farms and outbreaks among workers at processing plants could affect the food supply.

"I think our system is strong enough and resilient enough that it will adapt, but these days it is particularly challenging," she said.

"I do not worry that we will not have enough food ... but we might see some differences in the variety and, hopefully not, but maybe in the prices as well."

Yussuff said the government still needs to make sure temporary foreign workers, who travel to Canada for the spring planting, are given protective gear and proper health care and are set up in safe living conditions.

"We continue to raise concerns and [the federal government] is scrambling to try and address them," he said.

"If they're not careful, I think it might force countries in which these workers are migrating to come here to do this work to say, 'Hang on a minute.' Whether it's Jamaica or Mexico or Guatemala, those governments might intervene and say, 'We're not sending our people to the kind of conditions that are inadequate.'"

Ottawa, provinces opposed to invoking Emergencies Act

The briefing document was prepared as part of the federal government's consultations with the regions on the Emergencies Act, a step the prime minister has said he'd prefer not to take.

Last week, Trudeau sent a letter to the premiers explaining what invoking the act could entail — such as giving the federal government the power to order qualified people to provide essential services.

"It is our hope that we don't have to use it, ever," Trudeau said on Friday.

Hassan Yussuff, president of the Canadian Labour Congress, is opposed to using the Emergencies Act to force essential employees to work. (Ryan Remiorz/Canadian Press)

"We are seeing that the collaboration, the partnership among provinces and territories and the way we're moving forward on this means that we might not ever have to use the Emergencies Act. And that would be our preference."

The premiers vehemently opposed deploying those strict measures during a conference call last week and made that clear in writing today when they sent a letter to the prime minister.

"Premiers share the opinion that it is neither necessary nor advisable to invoke the act at this time," said the letter, signed by Saskatchewan Premier Scott Moe, chair of the Council of the Federation.

"You have the commitment of premiers to maintain the strong working relationship we have cultivated as we face the challenges of COVID-19 together. We seek to continue to strengthen this cooperation as Canada moves forward."

That cooperation has been playing out over much of the crisis. For example, Alberta Premier Jason Kenney has promised to send personal protective equipment to Ontario and Quebec, the two hardest-hit provinces.

The briefing document also says collaboration between the provinces and territories has been effective.

"However, as the crisis continues to worsen, some additional measures and greater intervention could become appropriate," notes the document.

Yussuff said he also opposes triggering the never-before-used Emergencies Act to force essential workers to stay on the job.

"I think if people are naturally concerned about their health we should listen to them because nobody should risk their life having to do their work," he said.

"The Emergencies Act is not going to solve the problem. What will solve it is collaboration and cooperation."