Should we all wear masks to slow COVID-19? Some experts are shifting their advice

Dr. Theresa Tam, Canada's chief public health officer, put it mildly when she tweeted on Wednesday evening, "There is a lot of discussion on use of face masks."

In these recent, destabilizing weeks, dramatic efforts to stop the spread of COVID-19 have prompted an onslaught of new, sometimes contradictory guidelines that seem to move as quickly as the virus itself. But even by pandemic standards, the conflicting opinions on whether we should all cover our noses and mouths in public are head-spinning.

On Friday, Dr. Gary Garber, an infection prevention and control physician at Public Health Ontario, said the agency, which provides scientific and technical expertise to the government, is "doing a scientific review of the issue," the latest indication that this question is very much a moving target. At present, Ontario's public health agency does not advise mask-wearing unless you have COVID-19 or are caring for someone with the virus.

"There's a debate amongst all the experts," said Margaret Sietsema, an expert on respiratory protection and an assistant professor at the University of Illinois at Chicago, who is on the "no" side of the masks-for-all discussion. "Who knows what's going on?"

To be clear, the question that a growing number of officials are now probing - as of Friday, this list included the U.S. Centers for Disease Control, Public Health Ontario and an advisory panel to the World Health Organization - is not whether the public should start donning medical masks.

With personal protective equipment (PPE) in short supply in many countries, including Canada, there is broad and powerful consensus among officials about the need to reserve medical-grade masks - including surgical masks and tight-fitting N95 respirators used in hospitals - for health-care workers on the front lines of the pandemic.

Unlike N95 masks, which contain a filter to protect the wearer, the growing #masks4all movement sees cloth masks as a means of protecting everyone else - a barrier, however imperfect, to catching infectious droplets from sneezes, coughs and exhalations. This position is gaining steam with emerging evidence about COVID-19 that suggests the virus may travel farther through the air than previously thought.

However, those on the other side of the debate argue there is no proof that cloth masks catch enough infectious droplets to make them worth the risks of encouraging universal mask-wearing. These risks include touching our faces more often to adjust masks, and imparting a false sense of security that could lead wearers to be less vigilant about physical distancing and handwashing - proven ways to stop the spread of COVID-19.

Thursday marked a break between officials in Canada and the U.S. on this issue, at least for the moment. After initially saying universal mask-wearing wasn't needed, U.S. President Donald Trump said he was planning to release new guidelines urging all Americans to don face coverings in public, based on a forthcoming recommendation from the Centers for Disease Control.

Then late Friday afternoon at his White House briefing, Trump said the Centers for Disease Control recommended that Americans use basic "nonmedical, cloth" masks on a voluntary basis, the New York Times reported.

"You can do it. You don't have to do it. I'm choosing not to do it," Trump said. "It's only a recommendation."

By contrast, the message from officials in Ottawa to Canadians is to wear homemade masks at their discretion - and with caution.

Health Canada released a notice on homemade masks on Tuesday, warning that because of the loose fit and materials used, "These types of masks may not be effective in blocking virus particles."

When Tam addressed the issue on Twitter on Wednesday, she acknowledged that a homemade mask may help with cough etiquette - akin to coughing into your sleeve. But she included several caveats, including the risk of masks becoming contaminated from the outside, and the fact that the virus can enter through the eyes. "Non-medical masks alone will not prevent #COVID19 spread," she wrote, urging the public to "consistently and strictly" adhere to frequent handwashing and physical distancing.

Tam and federal Health Minister Patty Hajdu reiterated this message during press briefings in Ottawa this week, repeatedly stressing the need to conserve medical masks for health-care workers.

In email Thursday, a spokesperson for Ontario's health ministry said: "There is no real evidence of the impact of homemade masks in preventing community spread, or in protecting oneself. While masks may reduce the frequency of an individual touching their nose or mouth, this potential positive effect is also tied to good hand hygiene."

The public health recommendations in Ontario are consistent with the current recommendations of the WHO. But that advice, too, may be in flux: Infectious diseases expert David Heymann, who chairs a panel of advisers to the WHO, told the BBC on Wednesday the group is considering emerging research on COVID-19 from the Massachusetts Institute of Technology, which suggests coughs can travel up to six metres and sneezes up to eight metres - four times the berth public health officials are recommending for adequate physical-distancing.

"The WHO is opening up its discussion again looking at the new evidence to see whether there should be a change in the way it's recommending masks should be used," Heymann told the BBC.

In an interview earlier this week, Garber, from Ontario's public health agency, said "it is hard to ascribe" evidence to the notion that getting everyone to wear masks helps curb the spread of COVID-19, and cautioned against drawing too heavily from success stories from some Asian countries, where mask-wearing is more widespread.

"Why in China did they put such a tight lockdown in Wuhan?" Garber said. "If masking was that effective, why didn't they just enforce that?"

In his email Friday, Garber noted a commentary published by the U.S. Center for Infectious Disease Research and Policy this week, which he said found "no evidence to support the plan" of universal mask-wearing. Co-authored by Sietsema, the commentary, which is based on a literature review on the subject, argues strongly against masks-for-all, because of the lack of scientific data showing that cloth - or surgical - masks contain infectious droplets well enough to make them worthwhile.

"Leaving aside the fact that they are ineffective, telling the public to wear cloth or surgical masks could be interpreted by some to mean that people are safe to stop isolating at home," the commentary states. "It's too late now for anything but stopping as much person-to-person interaction as possible."

But for every expert arguing against universal masking, there is a study that seems to make the case for the other side, although none is definitive or necessarily applicable in countries like Canada, where medical masks are in short supply.

On Friday, Benjamin Cowling, a public health professor at the University of Hong Kong, tweeted: "New study just out, face masks effective for source control against influenza and seasonal coronaviruses." In the paper published in Nature, Cowling and his co-authors write, "Our results indicate that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals."

However, for some experts, the lack of scientific data on the efficacy of cloth masks is not a reason to abandon the strategy. In Toronto, Michael Garron Hospital recently issued a challenge to east-end sewing enthusiasts to make 1,000 cloth masks to be distributed to approved hospital visitors and patients at discharge.

In a message on the hospital's website, Dr. Jeff Powis, medical director of infection prevention and control, says, "We want to see all east enders wearing a fabric mask when they need to be within six feet of other people, especially vulnerable populations and the elderly."

In response to questions from the Star about this initiative, Powis said in an email, "Unfortunately, there is no time for a randomized controlled trial to evaluate the efficacy of masking the public, and at this critical stage in the pandemic, a lack of definitive evidence will lead to inaction."

Powis added that cloth masks are "not a replacement for social distancing, or hand washing; it is additive to these interventions."

With files from Tonda MacCharles