We now find ourselves months into the COVID-19 pandemic since it was first declared on March 11th, 2020. As time moves forward, the global research community continues to devote effort and resources towards better understanding this disease. One important focus is to better understand the risk of transmission of the SARS-CoV-2 virus from infected to uninfected individuals.
How does COVID-19 spread?
The SARS-CoV-2 virus that causes COVID-19 can indeed be spread by droplets or aerosol particles in the air. But is our understanding of how the virus transmission correct?
Human history is full of examples where our initial understanding of infectious disease transmission was incorrect. For example, malaria is an infectious disease largely transmitted by mosquitoes. People wrongfully identified the poor and smelly air around stagnant water, marshes, and swamps as the cause of malaria – instead of the actual mosquitos that dwell and thrive in these settings. The word Malaria actually comes from the medieval Italian words “Mala” and “aria” and means “Bad air”…1 and the misnomer lives on!
Unlike malaria, the SARS-CoV-2 virus that causes COVID-19 can indeed be spread by droplets or aerosol particles in the air.
What is the difference between aerosols and droplets?
When someone coughs, speaks or breathes, they can send a spray of mucus and saliva droplets flying from their mouths. Droplets can measure a variety of sizes. Those that happen to be ≤10 micrometers in diameter are termed “respirable particles” and are capable of traveling beyond the upper airways towards the lower airways.2
Heavier droplet particles (especially those >20 micrometers in size) will be fare more likely to fall by mere gravity (landing on surfaces around the person). In contrast, aerosols are even smaller than droplets and can be suspended in the air for longer time. Think about indoor air fresheners and scented candles.3 Aerosols can also travel longer distances and can go even deeper into the lungs.
What we learned about the use of nebulizers during the SARS outbreak
Back in 2003, Toronto, Canada was the main North American site affected by the SARS outbreak. SARS was caused by a cousin virus of the one causing the current COVID-19 pandemic.
In the process of contact tracing at that time, it had become clear that providing the ‘rescue’ medication salbutamol to one of the earliest SARS cases in a Toronto emergency department by way of nebulization led to the transmission of SARS to other patients in nearby beds (approximately 1.5m-5m away).4 Nebulizers can create a large number of tiny aerosol particles (1-5 micrometers in size). These particles can carry viruses deep into the lungs and infect people nearby that breathe them in.5 Nebulization is an aerosolizing procedure. From the crucial contact tracing process of SARS in 2003 we have learned the important lesson of enforcing strict infection control precautions while treating patients with contagious viral illnesses.
How to properly use metered-dose inhalers
Nowadays, in the midst of the present-day COVID-19 pandemic, and with the benefit of hindsight, the Canadian Thoracic Society (CTS) has developed guidelines6 to inform both patients with asthma and COPD and healthcare workers alike on the best way to be using inhaled medicines without risking the spread of infection.
Specifically, it is recommended that salbutamol not be delivered by nebulizer, particularly in healthcare settings and particularly in those suspected or confirmed to have COVID-19. The use of metered-dose inhalers (MDI) is strongly encouraged, and in fact has become the standard ‘go-to’ method of delivering salbutamol in some Canadian provinces.5
Using a spacer device with the MDI is the best way to make sure that the medicine gets delivered into the lungs where it is most effective.
These CTS guidelines come at a very important time point in the pandemic. A very practical plan is laid out to face and potentially minimize the possibility of ‘rescue’ medication shortages.
After reading these guidelines it becomes clear that each of us has an important role to play in minimizing both infectious disease transmission and drug shortages. We are all in this together!
About the author
Bryan completed his medical school and Internal Medicine residency at the University of Toronto, and his Respirology fellowship at the University of Alberta. Prior to this he completed his undergraduate degree at Queen’s University and his master’s degree in Physiology at McGill University. He has had a longstanding clinical and research interest in respiratory and cardiac physiology and applied exercise science, in pulmonary rehabilitation, and in the management of chronic respiratory disease. He is currently completing an additional fellowship at the Montreal Chest Institute (McGill University Health Centre) in pulmonary rehabilitation and chronic disease management.