Initial Answers to the “Trillion-Dollar Question”: The Role of Aerosols in COVID-19 Transmission and Implications for Safely Reopening Shared Spaces
In an April 14 New York Times article titled “Stay 6 Feet Apart, We’re Told. But How Far Can Air Carry the Coronavirus,” Dr. Michael Osterholm, Director of the Center for Infectious Disease Research and Policy at the University of Minnesota, posed a question with enormous implications for global health and safety as we return to shared spaces in the absence of a vaccine and reliable rapid testing:
“The question is what does it take for you to get infected? And that I think is the trillion-dollar question we have…maybe all it takes is an aerosol. You don’t need any droplets at all.”
Dr. Osterholm highlights one of the critical “known unknowns” of COVID-19 – the transmission role of aerosols, or particles under five microns in diameter that are emitted while talking and breathing, that can stay suspended in air for hours, and that can travel over 20 feet.
Currently, guidance from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) of six feet separation in public assumes that large droplets from coughing and sneezing are the principal means of COVID-19 transmission and that most large droplets fall to the ground within six feet.
However, a chorus of prominent experts have emphasized the role of aerosols and airflow as another potentially important transmission vehicle for COVID-19, with emerging scientific research lending credence to their argument:
- “COVID-19 Outbreak Associated with Air Conditioning in Restaurant, Guangzhou, China, 2020”: Emerging Infectious Disease article stating that virus transmission “cannot be explained by droplet transmission alone,” suggesting the potential role of aerosol transmission.
- “Aerodynamic Analysis of SARS-CoV-2 in Two Wuhan Hospitals”: Nature article concluding that the virus “may have the potential to be transmitted via aerosols,” with “room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of COVID-19 in aerosols.”
- “The Airborne Lifetime of Small Speech Droplets and Their Potential Importance in SARS-CoV-2 Transmission”: Presentation to the National Academy of Sciences finding that “speech droplets generated by asymptomatic carriers by the virus are increasingly considered to be a likely mode of disease transmission.”
What does the airborne transmission of COVID-19 via aerosols mean for the air that we breathe in shared spaces that many people will return to?
On this matter, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), a leading professional association whose guidance is widely referred to by facility managers, published a position document on infectious aerosols in April stating:
“Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled. Changes in building operations, including the operation of heating, ventilating, and air-conditioning systems, can reduce airborne exposures.”
Given the complexity, urgency, and our evolving understanding of the risk presented by COVID-19 aerosols, practical application of ASHRAE’s guidance is easier said than done. In our experience, the airborne transmission risk is not always well-understood by facility managers and therefore insufficiently accounted for in reopening plans. Moreover, there is a notable gap in diagnostic tools available for safely assessing the risk of airborne transmission of COVID-19 indoors.
Based on groundbreaking technology developed with the support of the National Institutes of Health (NIH), our veriDART solution for verifying safe indoor airflows fills this gap. veriDART leverages proprietary airborne tracers that safely mimic the mobility of airborne pathogens like COVID-19 in order to identify high-risk transmission vectors, assess the efficacy of filtration and ventilation, and instill public trust and confidence in buildings for safe occupancy.
As we get closer to answering the “trillion-dollar question,” the potential risk of aerosols is a key health and safety planning consideration. Joseph Allen, Director of the Healthy Buildings program at Harvard T.H. Chan School of Public Health said, “The evidence suggests that mitigating airborne transmission should be at the front of our disease-control strategies for COVID-19.” veriDART is a powerful tool for facility managers as they gradually reopen buildings while preparing for a potential second wave of viral outbreak this fall.
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Erik has been a leader at the intersection of agriculture and technology in senior roles at Farmers Business Network, Cargill, and the White House. He is a co-founder of CrossBoundary, a leading frontier market investment advisor, and is a combat veteran and graduate of U.S. Army Ranger and Airborne Schools. He received his undergraduate degree from the University of Pennsylvania and a joint M.B.A. – M.P.P. from Harvard Business and Kennedy Schools.