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Are Canadian hospitals doing enough to prevent airborne spread of SARS-CoV-2?

Policy-makers recommendations for infection prevention and control measures mostly remain the same despite a recognition of the airborne transmission of SARS-CoV-2.

While federal, provincial and international public health agencies have all stated that SARS-CoV-2 can spread through airborne transmission, changes in policy to protect healthcare workers have been slow, some physician experts say.

Across Canada, most hospitals’ infection prevention and control (IPAC) policies recommend healthcare workers wear medical/surgical/procedure masks, with N95 respirators and their equivalents reserved for aerosol-generating medical procedures.

Even the term aerosol-generating medical procedures is being questioned. As the Canadian Association of Emergency Physicians (CAEP) point out in a December press release, dispersal of the virus is now better understood as a continuum rather than an aerosol versus droplet dichotomy. As such, a wide number of procedures may generate smaller SARS-CoV-2-laden aerosols that are airborne, so a better term is high-risk procedures, CAEP said.

CAEP changed their recommendations for PPE, saying N95 respirators (and equivalents) should be worn “in any clinical situation in which the patient presents as a high risk for COVID-19 transmission based on the clinical presentation, epidemiologic and environmental factors, and the treatments and procedures needed.” If enough N95 respirators are available, healthcare workers can choose to wear an N95 respirator at any time.

However, CAEP did not endorse mandatory N95 use for all patient encounters, stating that there was no evidence to support such a recommendation.

“I really think that if you’re working in a hospital, particularly in the emergency department where you’re at risk of exposure to COVID patients, that I think there really should be a transition to N95,” said Dr. Anna Banerji, a pediatric infection disease specialist and professor at the Temerty faculty of medicine at the University of Toronto. She has been working with COVID-19 patients since the pandemic began.

Read: Health experts urge more preventive action to curb aerosol spread of COVID-19

Since February, healthcare workers in areas where there is a person with COVID-19 or is suspected of having COVID-19 are required to wear N95 respirators, regardless if there is an aerosolizing procedure or not. The requirement came from Quebec’s workplace safety board (CNESST) after a legal challenge by Quebec’s nurses.

"I really think that if you’re working in a hospital, particularly in the emergency department where you’re at risk of exposure to COVID patients, that I think there really should be a transition to N95.”
Dr. Anna Banerji

As recently as Dec. 15, Public Health Ontario updated their recommendations on PPE use for healthcare workers caring for people with COVID-19 or suspected to have COVID-19. When providing direct care to these patients, healthcare workers are now advised to wear a fit-tested, seal-checked N95 (or equivalent) respirator. A well-fitted medical mask or non-fit tested respirator, is also appropriate, the statement reads.

Alberta Health Services continues to uphold IPAC recommendation that healthcare professionals should wear a medical mask in most settings, and reach for an N95 respirator only in cases of aerosol-generating medical procedures. An agreement with a number of healthcare professional unions in February 2021 means that all healthcare workers can use a fit-tested N95 (or equivalent) respirator in any setting or situation if they decide it is necessary based on a point of care risk assessment.

“I know there is a lot of controversy over N95s versus regular medical masks but our observation in the hospitals is that regular medical masks are working quite well as long as everyone is in a mask that has to be,” said Dr. Daniel Gregson, an infectious disease expert and associate professor at the Cumming School of Medicine in Calgary.

“The protocols that we have currently for people who are admitted, with droplet precautions, which we generally use in our COVID wards, appears to be working quite well,” he said. “The caveat to that is, when people show up without masks on, things can go south fairly quickly.” Dr. Gregson was asked to comment by The Medical Post.

Are the medical masks working to prevent airborne transmission?

Public Health Ontario notes in its Dec. 15 statement that there is not strong evidence supporting a significantly greater protective effect of N95 respiratory use over medical masks. Another way to measure this is to look at the number of COVID-19 cases in hospitals. A Public Health Agency of Canada report showed that 20% of Canada’s COVID-19 cases up until September 2020 were in people working in healthcare settings. However, that number decreased in the first half of 2021, when COVID-19 vaccination was ramping up.

A CIHI analysis of COVID-19 cases in healthcare workers from January 2021 to June 2021 shows that 6.8% of Canada’s COVID-19 cases were in healthcare workers. While lower than in 2020, this percentage is higher than the share of COVID-19 cases in healthcare workers out of total cases in France, Germany and the U.S., all as of June 2021.

A barrier to recommending N95 respirators is comfort. “Some people are calling for N95 masking all the time, and my observation is that, it may be easy for you to do, but hard for most people to mask with an N95 mask all the time,” Dr. Gregson said.

Dr. Banerji agreed discomfort was a deterrent. “It is trying to find the balance between something that can potentially kill someone and being practical if it is very uncomfortable to wear."

Read: Modifications to surgical masks improve filtering efficiency: study

While many centres and health authorities continue to advise healthcare professionals use medical masks for non-aerosol-generating medical procedures, the recommendations could always change.

“We review on a continual basis,” said Tammy Martins, executive director of quality and safety for the Saskatchewan Health Authority. “We actually have dedicated meetings twice a week to review recent evidence, research and learnings from other jurisdictions.”


Public Health Ontario acknowledges that PPE is the most visible of all the prevention and control measures, but is the last tier in a hierarchy of importance of measures. Ventilation comes before that. Improving ventilation to reduce airborne transmission of SARS-CoV-2 could include optimizing fresh air changes in the heating ventilation and air conditioning (HVAC) systems. The Canadian Standards Association has specific air change rate requirements for healthcare settings. Carbon dioxide monitoring by HVAC professionals can identify areas with poor ventilation, although high carbon dioxide readings does not indicate transmission risk, according to a May 2021 report on HVAC systems from Public Health Ontario.

Other indoor settings, such as schools, follow recommendations from the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE).

In April 2021, the federal government announced $120 million for better ventilation in public buildings, including healthcare settings. At Alberta Health Services facilities, ventilation is being continually assessed and improved, a spokesperson said.

One of the best ways to improve ventilation is open windows, if possible or appropriate. With the Canadian winter, it is not always feasible. “In South-East Asia I can open the windows, with screens, but I can’t do that in Alberta in the long term,” Dr. Gregson said.

Read: We studied how to reduce airborne COVID spread in hospitals. Here’s what we learnt

Another way to reduce airborne transmission is to use air cleaners for air filtration. A study published in Infection Control and Hospital Epidemiology suggests air filtration may reduce airborne transmission. In December 2020, Public Health Ontario said that portable air filtration “cleaners” should be able to remove SARS-CoV-2 particles from the air, reducing the risk of transmission. Portable air cleaners may be considered “in areas where sufficient ventilation is difficult to achieve.”

A study from the U.K. confirmed that portable air filters remove SARS-CoV-2 from the air. The study was conducted in a hospital with a high number of COVID-19 cases, and was published as a pre-print.

“This study suggests that HEPA air cleaners, which remain little-used in Canadian hospitals, are a cheap and easy way to reduce risk from airborne pathogens,” Dr. Davis Fisman told Nature in an October 8 article about the research. He was not involved in the research.


Infection Control and Prevention starts with elimination. If the public understands the airborne transmission of SARS-CoV-2, then people may be more likely to act appropriately to take action to decrease spread. It’s one thing to make a statement about airborne transmission, and another to actively promote the information to the public. For example, the U.K. mounted a campaign in November to “Stop COVID-19 hanging around.

With the rise of the omicron variant of SARS-CoV-2, policy-makers may soon implement the changes that many physicians have been calling for to reduce the spread of the virus. Public Health Ontario's December 15 recommendation to use N95 respirators may be the first of many changes before the two-year anniversary of the pandemic.

Read: Public needs info on how ventilation can prevent spread of COVID-19 says physician, engineer group

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