Ontario fought against treating COVID-19 as an airborne threat in hospitals — and won. With the fourth wave bearing down, was that the right move?

Amid Ontario's frightening rise in community infections early last December, staff at Hamilton's Juravinski Hospital were preparing to treat a second wave of incoming COVID-19 patients.

Instead, an outbreak happened inside the hospital's walls.

On Dec. 3, 2020, two patients tested positive on Ward B3, a rehab unit for patients with brain injuries. Meanwhile, that same day, on the opposite side of the hospital, four patients tested positive on Ward E3, a clinical teaching unit for patients with serious medical conditions such as dementia, stroke or heart failure. A pair of roommates in one room, a patient next door, and a fourth several doors down the hall, to the left.

Within days, the single strain of COVID was spreading throughout Juravinski's main building. It appeared next in a pair of roommates on F5, a unit for patients who've been stabilized, but can't be treated at home and might be waiting on transfer to a long-term-care home. On Dec. 10, it spread to E4 - surgical oncology. Staff there and on the other wards soon started testing positive, too.

Sixteen days after the outbreak had begun, the virus spread to a fifth and final ward, the hospital's musculoskeletal rehab unit in a separate building from the main.

In total, 106 patients and staff caught COVID in the multi-ward outbreak at Juravinski from Dec. 3-22. Nine died.

These totals make it neither the largest, deadliest nor longest lasting among hundreds of Ontario hospital outbreaks - but the Juravinski case is one of few with a public, detailed account of what happened.

The victims are among more than 500 Ontarians who have died after catching COVID in one of nearly 600 hospital outbreaks. That toll means that, after nursing and retirement homes, hospitals have been the deadliest single source of virus spread throughout Ontario's pandemic, but with little of the detailed public accounting that's followed in those sectors.

As the world looks toward the threat of a devastating fall with a more infectious variant, the tiniest details about hospital outbreaks like the one at Juravinski are fuelling a raging debate over how officials in this province, this country and globally have handled the worst health crisis in a generation.

As in nearly all North American and European jurisdictions, Ontario health officials decided early on to treat COVID as primarily spread by droplets, rather than as an airborne threat. In this, Ontario and others followed the World Health Organization, which tweeted in March 2020 FACT: #COVID19 is NOT airborne" and for months denied airborne spread was possible except during specific medical procedures.

The WHO advised that the pandemic could be controlled using the now-familiar steps of hand washing, social distancing and droplet precautions" exemplified by surgical masks and face shields. These have been key tools in the fight against COVID in Ontario hospitals ever since. In this province and elsewhere, the official position remains that the virus can be controlled without resorting to the stricter protocols hospitals already prepare to deploy against known airborne threats, like tuberculosis or measles.

The province's health officials remain steadfast this was the right call, then and now. They note the provincial guidelines for preventing COVID outbreaks are backed by the expert opinions of eminent Infection Prevention and Control (IPAC) professionals with years of experience controlling infectious disease inside Ontario hospitals.

The province has even gone to court to defend its position - and won, defeating a push by the Ontario Nurses' Association to force airborne protocols inside hospitals in May.

The province's approach is backed by the greater majority of experts who have been working throughout the pandemic implementing infection prevention and control measures across Ontario hospitals," said Dr. Jerome Leis, the director of IPAC at Toronto's Sunnybrook hospital. Leis, who gave his expert opinion supporting the province against the nurses' challenge, added: These experts have been quite silent on this question while being hard at work - but I think you will find that based on their direct experience, they agree with current Ontario guidelines."

The epidemiologists, physicists and aerosol scientists warning of airborne COVID tell a very different story, often loudly, often amplified by the social media hashtag #COVIDisAirborne and the drumbeat of new scientific research, including a major review in Science Thursday.

As they put it, the toll of hospital outbreaks like at Juravinski is no surprise: Health authorities failed to plan for the threat of airborne COVID, the researchers say, and patient deaths were a direct result.

Said University of Toronto epidemiologist Dr. David Fisman, who gave expert testimony in support of the nurses' court challenge: We were allowing people to get COVID and die in hospital in Wave 1. We responded to that by changing not a goddamn thing and we let it happen again in Wave 2."

If we had adopted the precautionary principle earlier on, we could have avoided this whole thing," said Linsey Marr, an American aerosol scientist who last summer signed an open letter warning the WHO of growing evidence of airborne transmission.

There will be history books written about this," added Australian aerosol physicist Lidia Morawska, the lead author of that letter.

But these voices are not winning the debate, at least not inside Ontario hospitals.

In a statement, Ontario's Ministry of Health says it believes the evidence strongly supports that the most effective way to reduce the risk of COVID-19 is the layered use of the currently recommended public health measures."

In short: As the province has entered a fourth wave, its hospitals are preparing to prevent new COVID outbreaks using substantively the same guidance on the airborne question they've relied on throughout the previous three.

The question of how COVID spreads from person to person is not just an esoteric debate. If the virus is, in fact, an airborne threat, that has profound consequences not just on how health workers should guard against infecting themselves, their colleagues and patients, but also on what we'll find when we try to understand how things went wrong.

The question matters because it is radically more difficult to control an airborne disease than one that spreads primarily at short range through what experts refer to as large respiratory droplets.

Any individual virus is tiny. But what matters more than size is how it travels from one person to the next. Many viruses need to be suspended in liquid - water, saliva, mucus - to remain viable. Such viruses can only be transmitted through the air in droplets, such as in the spray produced by a cough or a sneeze. These droplets are much larger than the virus itself; crucially, they're also heavier and affected by gravity.

If a virus is only transmitted by such relatively heavy droplets, familiar measures like surgical masks, distancing and sanitizing should control it. The largest particles in a sneeze won't spread beyond a couple of metres before they fall harmlessly to the ground. And where close contact with another person is necessary, a surgical mask with eye protection should be a sufficient barrier.

An airborne disease, on the other hand, can spread through much smaller particles or what gets left behind after a larger droplet evaporates.

In extreme examples, an airborne virus like measles can be exhaled into the air through talking or breathing and may linger in a space for hours, similar to cigarette smoke. Like large droplets, smaller virus-carrying particles will be by far the most concentrated at very close range - but they'll also float some distance through the air. These particles, often referred to as aerosols, can waft around hospital curtains, or out of one room into another via a shared ventilation system. And because aerosols can be expelled at any time, not just in a cough or sneeze, a patient may be infectious without outward symptoms.

This is why standard protocols to control an airborne disease instead rely on filtering the air - through the exclusive use of N95 respirators rated to catch 95 per cent of particles that might pass through a surgical mask, and high-quality ventilation systems that will regularly clear a space of virus - and much stricter patient isolation, such as negative-pressure rooms that prevent infectious air from leaking into adjacent spaces.

These steps can be difficult, and more expensive, but health authorities know this is how to control an airborne disease. For tuberculosis, for example, the latest guidance from the Public Health Agency of Canada demands a strict airborne protocol relying on single-patient isolation, negative-pressure rooms or, where these aren't available, rooms with portable HEPA filtration units, and the exclusive use of N95 respirators.

Both sides of the debate note the science of COVID's airborne risk is not black or white. It's a matter of where on the spectrum this virus falls. If airborne transmission is merely possible but only situationally, then COVID should be manageable with the status quo of droplet-based protocols, like Ontario's.

If, instead, airborne transmission is common - or even dominant - the calculation changes.

The Juravinski outbreak is an example of how two sides of the debate can look at the same evidence and reach opposite conclusions.

In a video presentation to a Hamilton Health Sciences staff town hall in April, the health network's medical director of IPAC, Dr. Dominik Mertz, describes how a single strain of COVID spread. You can watch how it sort of walked through our ward," Mertz says in the town hall, showing how infections popped up in Ward E3 seemingly at random.

This pattern suggests a vector" - staff, likely - was responsible for spreading the virus through the hospital in close contact with others, he says.

The pattern is not, he says, evidence these outbreaks were airborne. I know many people are, or were, very concerned about that." This means there's no evidence for the need for airborne PPE, so for N95 (masks)."

Fisman says he sees the opposite takeaway. The high number of simultaneous cases at the start of the Juravinski outbreak is evidence of an earlier upstream" event that infected several people all at once, he said. There had to have been missed infections before the first detected cases, he explained, otherwise there wasn't the time needed for the initial generation of patients to contract the virus, get sick and spread it to the next.

Basically, you've got a missed superspreader event here."

The key question, Fisman said, is to ask what's the most likely mechanism to explain that sudden explosion" of initial cases. If the Juravinski outbreak was spread by large droplets, that would require someone - likely staff - to have been walking throughout the hospital coughing and sneezing near several patients and colleagues in a short period of time, presumably while wearing PPE. The outbreak is much easier to explain if this initial wave of transmission happened without symptoms, he said.

A hypothetical example of a superspreader event could have happened in a staff common area, he said. Perhaps a nurse or doctor who didn't know they were infected spread the virus to colleagues who'd removed their masks to chat and eat. Those colleagues could then go to their wards and spread it to several patients in a single generation, he said.

Aerosol would do this quite easily," Fisman said. Otherwise you don't have these cases show up bang, bang, bang throughout the hospital." (Until this week, Fisman was a member of Ontario's science advisory table, from which he resigned.)

Mertz was not available this week to respond to the Star's follow-up questions. In a statement on his behalf, a hospital network spokesperson explained that appropriate infection control and prevention measures were implemented to manage the outbreaks at Juravinski, which had been caring for patients above its normal complement of funded beds, with multiple patients per rooms.

The spokesperson said that like all Ontario hospitals, Hamilton Health Sciences will continue to follow provincial direction as the pandemic evolves."

How can two sets of experts reach such different conclusions?

Many IPAC professionals say the critics are ignoring hospitals' on-the-ground experience managing, and defeating, COVID outbreaks.

In Toronto, Michael Garron Hospital's director of IPAC, Dr. Jeff Powis, explained that in his hospital's experience, the evidence is that outbreaks stop once patients are identified and treated using droplet and contact interventions. (This was also a key point in Mertz's presentation.)

Powis added that he has himself spent thousands of hours managing people with COVID over the last 18 months, so I also have spent that many hours wearing the personal protective equipment that I have other people wear, based on my role as medical director of IPAC, and I believed it was safe and would never have done anything I didn't think was safe (nor) ask anything of my staff that I wouldn't do myself."

For the critics, the debate is fierce in part because airborne" is a loaded word in our health systems. With measles, for example, the threat is so extreme that airborne spread can happen easily hours after an infected person has left a room - and hospitals understand and prepare for this risk.

Almost no one argues COVID's threat is quite that extreme, but the airborne" label is still weighed down by this comparison, said Marr, the American aerosol scientist. If a disease has the airborne label, hospitals know that an outbreak demands N95s for everyone and the widespread use of isolation rooms, and there simply are not nearly enough of those," she said.

But there are steps health officials can take to guard against the threat without needing to mandate the full airborne protocol - like Canada's TB guidance - which may be unworkable in a global pandemic, Marr said. One simple step is to act as if everyone coming into the hospital might be infected" and proactively have staff wear N95s in all interactions with people coming in, she said. Portable air filtration units can help lower the risk where dedicated isolation rooms aren't available, she added.

Of course, said Morawska, the risk for all transmission is higher the closer you are to an infected person - true for large droplets and airborne particles alike. If another patient or staff member is half a metre from an infected person and talking even for 10 or 15 seconds, you are inhaling this whole cloud," she said.

Asked whether she'd feel comfortable entering any hospital using droplet protocols without at least mandatory N95s, Morawska scoffed.

I would personally not enter any hospital without an N95."

IPAC professionals like Powis, Juravinski's Mertz and Sunnybrook's Leis are the point-people responsible for responding to and analyzing COVID outbreaks inside hospitals.

Through the Provincial Infectious Diseases Advisory Committee, IPAC experts are also the authors of detailed technical advice on how to respond to an outbreak. The latest version of these guidelines, updated in July, warns of the speed at which COVID can spread within health facilities and does acknowledge both large droplet and aerosol transmission, while generally emphasizing the rigorous use of contact and droplet precautions."

The guidelines note the province's rules for PPE, including N95 respirators, are the responsibility of the chief medical officer of health, as outlined in a separate document known as Directive 5."

This document, last updated at the height of Wave 3 in early April but relatively unchanged since October, was the focus of the nurses' court challenge. It requires health-care workers to wear N95s only during aerosol generating medical procedures," and although it gives workers a choice, it does not make them mandatory. (The document says nothing else on airborne risk.)

A key problem, says ONA president Vicki McKenna, is that Directive 5 makes nurses first perform a risk assessment before they can use an N95, a step that may itself be risky. Nurses and health-care workers should always be wearing an N95 if caring for presumed or COVID-positive patients, she said, adding that the nurses believe Directive 5 should have clearly stated that airborne transmission is a factor."

In court, Sunnybrook's Leis gave the key opinion opposing the nurses' argument, and in support of Directive 5. In his report, from April, he describes how Ontario hospitals have used droplet precautions for the care of confirmed COVID patients, mandating N95 masks only for some procedures, but giving individual health-care workers a choice.

Leis writes that available evidence and Ontario hospitals' experience treating several thousand COVID patients supports droplet and contact as primary modes of transmission."

He continues: While aerosols can play a role in transmission in some circumstances, our experience after 1-year of using the current Ontario PPE recommendations across health-care settings, is that they are appropriate and effective when used as part of the required hierarchy of controls."

I believe that the application of the precautionary principle to the risk of transmission of COVID-19 in health-care settings has been appropriately applied in Ontario based on the lessons learned from (the 2003 SARS outbreak)."

He notes specifically that Ontario COVID assessment centres did not see large numbers of infections among health workers, even though they exclusively used droplet protocols.

Asked by the Star to respond to critics' specific claims, Leis in an email pointed to several studies that support the conclusion that droplet and close contact precautions are sufficient: A paper from California that found no difference in positivity between health workers wearing typical protections and those wearing respirators; an Irish study that found most infections acquired in a hospital resulted from prolonged close contact; two case studies in which patients and health-care workers were present in situations that should have produced COVID-19 aerosols, but saw no follow-on infections; U.K. screening data that found similar infection rates among non-clinical and front-line staff; and Alberta data finding most health worker infections were from the community, not caught at work.

In a follow-up, he explained his opinion that mandating N95s for all health workers would be difficult to comply with across the board, compared to the current recommendations which regard droplet and contact precautions as a minimum and make N95 respirators accessible to any regulated health professional at any time based on their risk assessment."

Leis's opinion was endorsed in court by 29 other IPAC professionals representing 24 Ontario hospital networks, all of whom signed in agreement that COVID-19 is primarily transmitted via droplet and contact route in health-care settings, rather than through airborne transmission," and that Directive 5 follows the precautionary principle.

Powis, who endorsed Leis's report in April, told the Star it was a a very balanced view of the existing literature" at the time.

The nurses' court challenge was dismissed in May.

Outside Canada, one of the most compelling new studies favouring airborne spread in hospitals comes from the U.K., where Cambridge University Hospitals tested upgrading the surgical masks worn by staff in COVID wards to FFP3 respirators - equivalent to an N99 rating.

The results, yet to be peer-reviewed, were staggering: staff saw a drop in infection of up to 100 per cent.

It's certainly consistent with aerosol spread," said Dr. Mark Ferris, an occupational physician at the university's Occupational Health Service and an author of the study.

He said his team decided to apply the precautionary principle and publicize the results before peer review. However, in July, Public Health Ontario published a five-page critical analysis highlighting issues with the study, noting that because it had not been peer-reviewed the findings should be interpreted with caution."

Earlier this month, a study in the journal Clinical Infectious Diseases found the most direct evidence yet of COVID's airborne potential. Researchers at the National University of Singapore found that fine aerosols generated by infected COVID patients talking and singing contained more of the virus than larger coarse" particles.

Our study demonstrates that SARS-CoV-2 can be aerosolized in the absence of coughing, sneezing, and aerosol-generating medical procedures," they wrote. Thus, exposure to fine aerosols should be mitigated," especially indoors.

Most recently, on Thursday, the journal Science published a significant new review of the current research on how COVID-19 spreads.

In it, the researchers cite published evidence showing a strong effect of ventilation on transmission; a clear difference between indoor and outdoor risk; documented cases of long-range transmission; observed infections despite the use of masks and eye protection; examples of superspreader events; and evidence from animal experiments and airflow simulations that each provide strong and unequivocal evidence for airborne transmission."

Weighing this research, and a lack of similar evidence demonstrating that larger droplets or contaminated surfaces can spread COVID-19, the authors conclude: we must acknowledge that airborne transmission is much more prevalent than previously recognized."

They add: Given all that we have learned about SARS-CoV-2 infection, the aerosol transmission pathway needs to be reevaluated for all respiratory infectious diseases. Additional precautionary measures must be implemented for mitigating aerosol transmission at both short and long ranges, with particular attention to ventilation, airflows, air filtration, UV disinfection, and mask fit. These interventions are critical tools for ending the current pandemic and preventing future outbreaks."

To many IPAC experts in Ontario and elsewhere, the case for airborne COVID has been unconvincing. Dr. Susy Hota, University Health Network's medical director of IPAC, also emphasized that it's been incredibly difficult to have respectful, open discourse" about the question.

Hota, who also endorsed Leis's opinion in the nurses' court challenge, on Thursday added in an email to the Star that the issue can't be resolved in black and white terms of droplets vs. aerosols, or surgical masks vs. N95 respirators.

She wrote: I recognize that the debate around transmission modes of SARS-CoV-2 is causing confusion, fear and frustration amongst the public. I wish I could make it all go away! I do believe that everyone is advocating in good faith for what they think is the right approach, but the entirety of science, real-life experience, feasibility and unanticipated consequences is not always being considered. It is far from straightforward and anyone who suggests otherwise may be missing important aspects."

It's been nearly two years since the pandemic broke out in China, and 18 months since the WHO first said COVID is NOT airborne." In the time since, scientists have uncovered evidence on both sides; the WHO has significantly walked back that initial position; new, more transmissible variants have emerged; and Ontario hospitals have fought off second and third waves bringing hundreds of new outbreaks and hundreds of deaths.

And they're preparing to do it again this fall.

Ed Tubb is an assignment editor and a contributor focused on crime and justice for the Star. He is based in Toronto. Follow him on Twitter: @edtubb

Kenyon Wallace is a Toronto-based investigative reporter for the Star. Follow him on Twitter: @KenyonWallace or reach him via email: kwallace@thestar.ca