WHO Changes Guidance On Possibility Of Airborne Transmission Of COVID-19

COVID-19 & Toronto Real Estate, Real Estate

Welcome to my blog on housing, culture, and design in Toronto, where I share my insights, ideas and point of view on the many facets of the Toronto Real Estate Market!

At the time of this writing, we’re four months into our new way of living and working, as the world strives to survive and prevent the spread of COVID-19. At this point, what we understand about the pathogen is just in its infancy, as is our capacity to mentally, emotionally, and spiritually process the potential magnitude of what living through a global pandemic looks like. Most of us understand that until there are accurate reliable tests aplenty which quickly confirm we have – or have had – the virus, governments develop real-time tracking data to reduce or limit the risk of those infected from exposing others to the virus, and humanity’s expert scientists develop a COVID-19 vaccine which is trial-tested, approved, licensed, and manufactured at a global scale…. we’re going to have to be hyper-vigilant in taking precautions with a commitment to self-isolating and social-distancing. Personally, I suspect we may witness concentrated outbreaks popping up in places randomly for the foreseeable future leaving us anxious and stressed as we collectively navigate our health and wellness in a world where Mother Earth reminds humanity that our culture of consumption is wreaking havoc on nature’s life balance.

One thing that we have learned about COVID-19 over the last several months is that it is always a rapidly evolving situation, as more cases emerge and the research and medical communities work diligently to learn more about how to treat and prevent this virus.

Just recently, I wrote about HVAC systems and how they could potentially play a role in the transmission of COVID-19 in Dear Urbaneer: Can I Be Exposed To COVID-19 From HVAC Systems?. While there has yet to be conclusive evidence that COVID-19 is airborne, the debate is gathering steam and credible theories are suggesting that airborne transmission could play a role in spreading the disease.



In the days immediately following the publishing of my post, there was breaking news that a group of 239 well-respected professionals (including doctors, scientists, and engineers) had written an open letter entitled ‘It Is Time to Address Airborne Transmission of COVID-19′. This group felt that the probability of the role of aerosols in COVID-19 transmission was too great to ignore and that bodies of influence (like the WHO) should be issuing guidance around this method of transmission in much the same way that they have advised on hand-washing, physical distancing, and mask-wearing as effective ways to prevent the spread of the virus.

In Ontario, this is particularly timely as we move into Stage 3 re-opening, where more people will be returning to workplaces and many of our indoor activities. In the open letter, the group acknowledged the efficacy of handwashing and social distancing as a means of prevention of the spread of COVID-19. However, they suggest by completely discounting the possibility that microdroplets produced by infected people have the ability to linger in the air for some time after they are produced creates a new set of risks.

Larger droplets fall to the ground, but droplets less than 5 micrometres in diameter become aerosols and have the ability to travel distances and remain in the air. The danger of spread increases if the aerosols are pushed along by a mechanical system (i.e. an HVAC), or through a person talking, shouting or singing.



This excerpt was taken from that open letter: “Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are released during exhalation, talking, and coughing in microdroplets small enough to remain aloft in the air and pose a risk of exposure at distances beyond 1 to 2 meters (yards) from an infected individual. For example, at typical indoor air velocities, a 5 nanometre droplet will travel tens of meters, much greater than the scale of a typical room, while settling from a height of 1.5 metres (about five feet) to the floor.”

The group that wrote the letter recommended that public places (like offices, retirement/long term care homes, schools, hospitals, etc.) need to have an appropriate amount of ventilation, with an emphasis on clean air supply and minimizing the recirculation of air.  Additionally, they suggest local exhaust, high-efficiency air filtration, and germicidal ultraviolet lights are in place to aid in protecting against the spread of the virus. They also recommend that indoor spaces not be too crowded, which is consistent with physical distancing. Front line workers should wear N95 masks to protect against aerosol particles.

Here’s a summary of the most important points, courtesy of CNN: “Coronavirus Can Float In Air And WHO And CDC Should Tell People That, Experts Say.”




WHO Responds to Open Letter

In response to the open letter, the WHO acknowledged that there are still a number of unanswered questions around how COVID-19 spreads and said that more research needs to be done to fully understand how it works and how to best prevent it. However, they agreed that there is enough evidence to consider airborne transmission sufficiently probably that they would advise on how to prevent spread through this method.

The WHO authored their own response to the open letter called, “Transmission Of SARS-CoV-2: Implications For Infection Prevention Precautions.”

In this press release and executive summary of the report, the WHO says:

“Indoor crowded spaces have suggested the possibility of aerosol transmission, combined with droplet transmission, for example, during choir practice in restaurants or in fitness classes. In these events, short-range aerosol transmission, particularly in specific indoor locations, such as crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out.”

As a result, the WHO has released new guidance around aerosol transmission. It doesn’t change a whole lot in terms of prevention. You should still wash your hands, avoid crowded places, physically distance and stay home if you are sick. This new guidance though does add an extra layer of credibility behind the efficacy of masks, especially in crowded, poorly ventilated places. It’s also important for health care workers to wear N95 masks and perform acts like intubation, where they are at high risk of encountering infected droplets and/or aerosols, in well-ventilated areas.

This underscores how nimble this virus is, and how we as a society need to consider all possibilities as we learn to live with it for the foreseeable future.




Media Response

After the open letter and the WHO change to guidance, there were a lot of pundits and experts weighing in about this shift in focus.

The consensus seems to be that, while airborne transmission isn’t the dominant method of spread like it is for other highly contagious diseases like measles, chickenpox and tuberculosis, it does play a role. This is particularly true when in combination with the other documented methods of transmission, like droplets expelled by an infected person.

In this NBC News article, What Is airborne Transmission? WHO Adds Guidance On ‘Aerosols’ In Coronavirus Spread the point was made that, although airborne transmission is very much possible, it’s likely not significant. If it was, many, many more health care workers would have fallen ill after working with infected patients, as they focused very specifically on protecting themselves against droplet transmission and not as much against aerosol transmission.

Nature.com released this article entitled, Mounting Evidence Suggests Coronavirus Is Airborne — But Health Advice Has Not Caught Up; it dives a little more deeply into the theory around airborne transmission and that this current stance goes against what medical professionals and engineers have thought since as far back as the 1930s around respiratory influenza diseases, which are believed to be transmitted through bigger droplets.

The evidence here comes from a case in Seattle in early March. At choir practice choir members washed their hands and didn’t physically contact each other (handshakes/hugs), yet 33 choir members contracted COVID-19 and two died. Some scientists believe that this points to a super-spreader event, as singing would create aerosols, and the length of the choir practice and poor ventilation could account for the large number of people falling ill.



In this CBC article, “Controversy Over Airborne Transmission Of COVID-19 ‘A Tempest In A Teapot,’“, B.C.’s Dr. Bonnie Henry feels that some of the controversy surrounding airborne transmission is a bit “overblown”. But she does comment on how she hopes that this will compel people to wear masks as well as drive design innovation to create more effective masks that are easier to wear, particularly for health care workers.


Here are some other interesting reads about the new position on airborne transmission:

“COVID-19: Top Science Stories Of The Week – From Airborne Transmission To Why We Should All Wear Masks” by WeForum.

“WHO Now Says Airborne Transmission Of COVID-19 May Be Possible In Some Settings. A Toronto Infectious Diseases Expert Explains And Offers Advice” by The Toronto Star

“New WHO Report Says Airborne Coronavirus Transmission ‘Cannot Be Ruled Out’ In Outbreaks In Some Indoor Settings” by CNN.

“Scientists Studying COVID-19 Raise Concerns Over Airborne Transmission” by The Globe & Mail.


This new position from the WHO really echoes what I talked about in my original post: while we can’t conclusively say yet that airborne transmission is a critical factor in the spread of COVID-19, the probabilities are strong enough that you should take extra precautions in how you live, work and operate indoors.

I’ve written about how COVID-19 will likely change our built environments in How COVID-19 Will Likely Change How We Design Our Homes that looks at how our home and office designs may be forever altered post-pandemic to improve on health, safety and comfort. By the same token, we may want to consider taking extra measures at home and work in order to protect ourselves, as I outlined in Dear Urbaneer: Can I Catch COVID-19 From HVAC Systems?– in this case against the possibility of airborne transmission, including having high-quality filters on your HVAC system, using portable air filters, installing UV lights and making sure that your home or office is properly ventilated. Ideally, having access to fresh air is preferable.

For proper protection, you combine these methods with handwashing, physical distancing and mask-wearing.


***ADDENDUM September 21, 2020 ***

Here’s a news article from the Ottawa Citizen about new U.S. data that confirms the concerns of the scientific body regarding airborne transmission of COVID-19, and affirms the recommendations of the WHO: “Virus Spreads Mainly Through Air, Says New Report From U.S. Agency


***ADDENDUM November 2, 2020 ***

We knew it!! COVID-19 brings ‘connection between the built environment and health’ back into focus, says the CBC:  “How the pandemic has put building design and ventilation back into the public health conversation.



Here are my most recent COVID-19 related blogs:

Dear Urbaneer: Can I Be Exposed To COVID-19 From HVAC Systems?

Demand For ‘Forever Homes’ In Toronto’s Downtown Family Neighbourhoods Persists Despite COVID-19

How COVID-19 Will Likely Change How We Design Our Homes

With COVID-19 Outbreaks In Long-Term Care Facilities, Is Multi-Generational Housing Better?

Assess Your Risk: Buying & Selling Toronto Real Estate During The COVID-19 Pandemic



My approach to real estate is comprehensive; it’s focused on research and keeping informed about all kinds of influences on our homes. Considering the possibility that airborne transmission and our HVAC systems, I did research to provide my readers with the most up-to-date information. That this question was thrust into the spotlight and the conclusions re-confirmed shortly thereafter only shows how important it is that we think about how and where we work and live in a new context. We’re here to help!



May my team and I be your realtors of choice?

With decades of experience navigating the ever-changing Toronto real estate market, a commitment to promote the sale of properties like yours with interesting and relevant information, and the ability to guide Buyers with credible insights and well-informed guidance, we are here to help without pressure or hassle.

Please consider our services!


Thanks for reading!


-The Urbaneer Team

Steven Fudge, Sales Representative
& The Innovative Urbaneer Team
Bosley Real Estate Ltd., Brokerage – (416) 322-8000

– we’re here to earn your trust, then your business –


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