Closing the border and telling the public to self-isolate at home in the early days of Canada's COVID-19 outbreak would have done more harm than good, according to a national public health organization.

Ian Culbert, executive director of the Canadian Public Health Association (CPHA), told a virtual committee of MPs today that while critics have said the federal government should have acted sooner, there would have been "very little" public support for strict measures in the middle of January, which could have undermined health officials' efforts when the situation became more dire.

"Low public support would have led to low-level adherence and a diminished support for any future interventions," he said. "Slowly, you have to change people's thinking ... that takes time. It takes evidence. You have to prove to people that it's serious."

The House of Commons health committee is studying Canada's response to the COVID-19 virus to ensure the federal government learns lessons that can be applied to the next pandemic. The Liberal government has faced criticism for waiting until the eve of Ontario's March break to tell people not to travel. The Conservatives have accused the Trudeau government of failing to restrict public gatherings soon enough and waiting too long to impose tougher measures at the border.

After critics accused it of lax screening at airports for returning travellers, Quebec Premier François Legault sent his own public health officials and police to airports to warn travellers to self-isolate for two weeks. This week, B.C. Premier John Horgan took it a step further and imposed a new legal requirement forcing travellers to present formal self-isolation plans to authorities at airports and border crossings.

Culbert said while public health officials' incremental approach has been attacked, he believes it was backed up by evidence.

Culbert said it's hard to change human behaviour — especially in Canada's case, given that the pandemic started halfway around the world in China. Canadians felt a sense of "insulation," he said. That attitude carried on even when Canada reported its first cases in British Columbia and Ontario, he added.

"There's a sense of them and us," he said. "Slowly, you have to change people's thinking. There's no them and us. It's a 'we' situation."

He turned to an example from the 20th century: when Canadians with tuberculosis were forced to leave their families and isolate in sanatoriums, he said, many avoided public health authorities as a result, which spread the disease further.

"This shows coercive actions can only be used as a last resort," he said.

Watch: 'This will be the new normal until a vaccine is developed': Trudeau

Prime Minister Justin Trudeau says it will take months of Canadians' "continued, determined effort" to follow pandemic measures such as physical distancing to overcome COVID-19. 1:55

There's been a "massive cultural change" over the last century in the public's attitudes toward science and health authorities, Culbert added. But he pointed to the anti-vaccination movement as a current example that shows public health officials can't just tell people what's good for them and expect them to listen.

"Just telling people the right thing to do doesn't work anymore," he said. "We have to convince people. It takes time, unfortunately ... but it's actually what works."

'We're just trying to strengthen the message': Tam

Conservative MP Tamara Jansen questioned the government's incremental approach to the restrictions.

Jansen said that in January, the Langley Chinese Cultural Arts Association cancelled a large event proactively before Chief Public Health Officer Dr. Theresa Tam banned large gatherings.

She also said that, early in the outbreak, members of the Chinese community in B.C.'s Lower Mainland were picking up people at the airport returning from China to ensure they didn't take cabs. They were also buying them groceries so they didn't go to the grocery store, she said.

"They were begging me to get the government to be more proactive," said Jansen.

"This was all done on a completely voluntary basis. Is it possible it was a misjudgment of [the] willingness of Canadians to self-isolate that this didn't go quicker?"

Watch: Tam and Freeland explain how closing the U.S. border helped fight COVID-19:

Dr Theresa Tam Canada's Chief Public Health officer and Deputy Prime Minister Chrystia Freeland spoke with reporters on Thursday 2:12

Culbert said this particular community likely felt directly affected because of their ties to the epicentre of the outbreak in Wuhan, China.

"You're talking about a highly sensitized community," he said. "They had a direct connection [to] what was happening in China and were very much aware. Many Canadians were not that connected and [were] thinking of it as a problem on the other side of the country."

Dr. Tam, meanwhile, was asked at a press conference today if she's recommending the government enact even stricter measures.

Tam said she's working with her provincial and territorial counterparts to monitor the trajectory of the pandemic and figure out how effective the current measures are. She said innovative studies are underway to track how well Canadians are following those measures, which could point to places where they can be bolstered.

Watch: Trudeau asked how should Canadians react to many more months of shutdowns:

Prime Minister Justin Trudeau spoke with reporters on Thursday. Earlier federal officials released models which predict many more months of self distancing needed to fight the virus. 2:30

"We're just trying to strengthen the message to Canadians that really you should avoid all non-essential travel and stay at home as much as possible during this critical period," she said.