Chrystia Freeland said Tuesday that chief public health officers have become "this generation's rock stars." And as long as rock stars have existed, there have been rock critics.

Those with learned expertise rightly come to the fore in a public emergency. In a world of sickness and fear, the epidemiologist is king.

But challenges to that expertise were always inevitable — and are probably even healthy.

Experts are not infallible. On matters that transcend popular opinion, they're also the best we've got.

Alberta Premier Jason Kenney is not an expert in infectious diseases. On Monday, however, he decided to publicly question the wisdom of someone who is — Dr. Theresa Tam, Canada's chief public health officer.

Alberta Premier Jason Kenney says he isn't going to wait for Health Canada to play catch up with other credible health regulators before pursuing potential coronavirus tests or treatments. 3:38

Pushed to defend his decision to allow Alberta doctors to use tests that have not yet been approved in Canada, Premier Kenney decided to attack Dr. Tam directly over how she reacted initially to the COVID-19 outbreak and how she has advised the federal government.

"This is the same Dr. Tam who is telling us that we shouldn't close our borders to countries with high levels of infection and who in January was repeating talking points out of the [People's Republic of China] about the no evidence of human-to-human transmission," Kenney said.

Unanswered questions

This isn't the first time Kenney has criticized someone in Ottawa since he decided to enter provincial politics, of course — but it is the first time he's challenged a non-partisan health official and there's much to unpack in his comments.

There are significant unanswered questions about China's actions and the World Health Organization's handling of the initial outbreak. And it's true that the human-to-human transmission of COVID-19 was only confirmed by Chinese officials on January 20.

But Kenney seems to be implying here that Dr. Tam should have somehow been ahead of both China and the WHO on describing the outbreak — or that she was easily duped by the Chinese government.

Even if either of those charges could be sustained, it's not clear how that would have any bearing on Canada's current situation.

Chief Public Health Officer Theresa Tam responds to a question during a news conference in Ottawa on April 13, 2020. (Adrian Wyld/The Canadian Press)

More obviously relevant (at least in theory) is Kenney's criticism of Tam's early approach to the idea of closing Canada's borders to slow the pandemic.

Dr. Tam did say publicly that closing borders is an ineffective response to a contagious disease. But she was hardly the only one saying it.

"We look at the United States, we look at Italy, for example — both countries [that] had bans on people coming into the country from certain other countries," Dr. Bonnie Henry, the chief health officer in British Columbia, said on March 3. "Those don't work."

When did Kenney speak up?

Asked Tuesday whether Kenney had expressed his views on closing borders before this week, the premier's office suggested he had conveyed his thoughts privately — but pointed to public comments he made on March 12 and March 13.

"I also discussed with the deputy prime minister my belief as the former immigration minister that there should be some tighter control of our borders, particularity from countries with very high levels of infections," he said on March 13.

By that measure, Kenney was just a few days ahead of the Trudeau government: on March 16, Ottawa announced a ban on travellers from countries other than the United States. Days after that, the ban was extended to all non-essential American travel.

Speaking with CBC's Power & Politics on Monday, Kenney suggested Canada should have followed "the lead of jurisdictions like South Korea, Taiwan, Singapore, and others who closed their borders from countries with a high rate of infection months earlier than Canada did."

You can't fight a virus simply by closing the gates

Comparisons between countries call for caution (in terms of geography and size, Canada and Singapore don't have a lot in common) but a global view might also underline the complexity of responding to a global pandemic.

South Korea, for instance, did implement a ban on travel from China's Hubei province — the epicentre of the COVID-19 outbreak — in early February, but it stopped short of a total ban on Chinese travellers. Its national government also struggled badly with its initial response to the virus.

A month later, South Korea was being held up as a model for other countries to emulate — largely because of a massive effort built around domestic testing and extraordinary surveillance.

As Dr. Henry noted in March, the United States and Italy both banned travellers from China. Both have fared much worse than Canada.

That doesn't prove that closing the border was necessarily a mistake, but it does suggest that responding to a pandemic might not be as simple as turning travellers away.

Is there any evidence that not banning foreign travellers from China led to a higher rate of infection or death in Canada? Maybe only an official inquiry or Royal Commission will be able to answer that in hindsight.

A shift in the official message

But according to the Ontario government, just five of the people who have tested positive for COVID-19 in that province so far had travelled recently to China — the same number of cases that could be linked to Costa Rica, Ecuador and Jamaica. By comparison, 383 people in Ontario who tested positive for COVID-19 had recently been to the United States, while 119 had returned recently from the United Kingdom.

Questions about border restrictions and travel bans likely persist because the position of federal officials changed — from arguing that such measures were not an effective response to joining other countries in implementing tight controls. Whether border policies had any impact on the spread of COVID-19 in Canada or not, that change in messaging has never been thoroughly explained.

Political leaders are likely to be applauded for deferring to experts in moments like this and non-partisan experts are generally given a higher degree of public deference. But trust can't be taken for granted and decisions need to be explained fully — particularly when those decisions change.

Experts might even disagree among themselves — but even that can be acknowledged and explained.

Politicians also can't assume that pointing to the advice of experts will allow them to escape accountability. Ultimately, it's elected governments that will be held responsible if efforts to combat COVID-19 seem to fail markedly. Privately, at least, government ministers need to be sure they're getting the best advice.

But all leaders are now deeply dependent on those experts for advice. They also rely on them to explain to the public why difficult decisions are being made, why schools are closed and people are being told to stay home. For as long as this pandemic lasts, the credibility of public health officers will be crucial.

So if a premier or prime minister wants to publicly criticize the counsel that those experts are providing, they had better be sure they're right and the criticisms are warranted.