Consideration of the Aerosol Transmission for COVID-19 and Public Health
Elizabeth L. Anderson,1,∗ Paul Turnham,1 John R. Griffin,1 and Chester C. Clarke2
ABSTRACT: This article analyzes the available evidence to address airborne, aerosol transmission of the SARS-CoV-2. We review and present three lines of evidence: case reports oftransmission for asymptomatic individuals in association with studies that show that normal breathing and talking produce predominantly small droplets of the size that are subject to aerosol transport; limited empirical data that have recorded aerosolized SARS-CoV-2 particles that remain suspended in the air for hours and are subject to transport over distances including outside of rooms and intrabuilding, and the broader literature that further supports the importance of aerosol transmission of infectious diseases. The weight of the available evidence warrants immediate attention to address the significance of aerosols and implications for public health protection.
CONCLUSION
Our current state of knowledge about the role of aerosols in the transmission of SARS CoV-2 warrants urgent attention.
Three lines of reasoning provide a weight of evidence that aerosol transmission is an important pathway of disease communication and may be significant
for the transmission and control of SARS-CoV-2:
1. Case reports of asymptomatic individuals passing on SAR-CoV-2 to infect others in association with studies that show that normal breathing, talking, etc. produce small droplets in the size range of predominantly <1 µm that are subject to aerosol transport.
2. Limited empirical data that have recorded aerosolized SARS-CoV-2 and SARS-CoV-1 particles that remain suspended in the air for hours and as such are subject to transport over long distances including outside of rooms and intra-building.
3. Support from the broader literature that reports the importance of aerosol transmission of infectious diseases and explores survival time and distances, concentrations of infectious agent the effects of temperature and humidity, and implications of dose delivery of various particle sizes to the respiratory tract.
To date, guidance and public health information has not focused specifically on aerosols as a potentially significant transmission pathway. The absence of the prevalent symptom of coughing and sneezing in asymptomatic individuals turns attention to aerosol transmission, predominately associated with breathing and talking, where the role of small aerosol transport may bemostprevalent.
In the interest of curbing the spread of COVID-19, the currently available evidence strongly suggests the immediate need to address the significance of SARS-CoV-2 aerosol transmission. The weight of
evidence suggests that sufficient inhalation protection could be important to curb COVID-19 and to refine guidance.
RECOMMENDATIONS
1. Collect data to explore the concentration, duration of survival, and transport distances for SARS-CoV-2 in aerosol form under differingconditions of temperature and humidity.
2. This work should be low cost and results available in a relatively short time.
3. If aerosols are confirmed as an important transmission pathway for SARS-CoV-2, further explore airborne concentrations and the role of dose to various parts of the respiratory trace in the progression and severity of the disease.
4. This information may inform public policy and earlier treatment decisions.
5. Investigate the potential for aerosol contamination of buildings, rooms, and surfaces to provide a basis for decontamination and related public health protective decisions and guidance.
6. Explore and record data to determine the role human activities play in potentially generating aerosols capable of transmitting SARS CoV-2 in both enclosed and open spaces. The evidence that supports the hypothesis that aerosol transmission may be occurring in encloses spaces does not preclude the phenomenon from occurring in larger enclosed spaces (arenas, churches) or even open spaces. The above referenced choir’s incidence rates may have been affected by higher exposures, and possibly high exposure deep into the lungs due to higher inhalation rates, despite lower concentrations in aerosols that might be postulated for asymptomatic individuals. The same might be said for persons exercising. Higher air flows in open or larger spaces would have a diluting effectdepending on important factors including wind speed, humidity, and temperature.
7. In light of the current weight of evidence that aerosols can transport SARS-CoV-2, and as new evidence emerges, further explore appropriate measures to curb inhalation exposure to small aerosols, including 5 µm or less, within buildings, rooms, and surfaces where these aerosols might travel and settle.
As more detailed information becomes available, longer-term protective strategies for curbing the transmission of SARS-CoV-2 and incidence of COVD-19 can be developed. The weight of the currently available evidence warrants immediate
attention to address the significance of aerosols with important implications for public health protection.
Elizabeth L. Anderson,1,∗ Paul Turnham,1 John R. Griffin,1 and Chester C. Clarke2
ABSTRACT: This article analyzes the available evidence to address airborne, aerosol transmission of the SARS-CoV-2. We review and present three lines of evidence: case reports oftransmission for asymptomatic individuals in association with studies that show that normal breathing and talking produce predominantly small droplets of the size that are subject to aerosol transport; limited empirical data that have recorded aerosolized SARS-CoV-2 particles that remain suspended in the air for hours and are subject to transport over distances including outside of rooms and intrabuilding, and the broader literature that further supports the importance of aerosol transmission of infectious diseases. The weight of the available evidence warrants immediate attention to address the significance of aerosols and implications for public health protection.
CONCLUSION
Our current state of knowledge about the role of aerosols in the transmission of SARS CoV-2 warrants urgent attention.
Three lines of reasoning provide a weight of evidence that aerosol transmission is an important pathway of disease communication and may be significant
for the transmission and control of SARS-CoV-2:
1. Case reports of asymptomatic individuals passing on SAR-CoV-2 to infect others in association with studies that show that normal breathing, talking, etc. produce small droplets in the size range of predominantly <1 µm that are subject to aerosol transport.
2. Limited empirical data that have recorded aerosolized SARS-CoV-2 and SARS-CoV-1 particles that remain suspended in the air for hours and as such are subject to transport over long distances including outside of rooms and intra-building.
3. Support from the broader literature that reports the importance of aerosol transmission of infectious diseases and explores survival time and distances, concentrations of infectious agent the effects of temperature and humidity, and implications of dose delivery of various particle sizes to the respiratory tract.
To date, guidance and public health information has not focused specifically on aerosols as a potentially significant transmission pathway. The absence of the prevalent symptom of coughing and sneezing in asymptomatic individuals turns attention to aerosol transmission, predominately associated with breathing and talking, where the role of small aerosol transport may bemostprevalent.
In the interest of curbing the spread of COVID-19, the currently available evidence strongly suggests the immediate need to address the significance of SARS-CoV-2 aerosol transmission. The weight of
evidence suggests that sufficient inhalation protection could be important to curb COVID-19 and to refine guidance.
RECOMMENDATIONS
1. Collect data to explore the concentration, duration of survival, and transport distances for SARS-CoV-2 in aerosol form under differingconditions of temperature and humidity.
2. This work should be low cost and results available in a relatively short time.
3. If aerosols are confirmed as an important transmission pathway for SARS-CoV-2, further explore airborne concentrations and the role of dose to various parts of the respiratory trace in the progression and severity of the disease.
4. This information may inform public policy and earlier treatment decisions.
5. Investigate the potential for aerosol contamination of buildings, rooms, and surfaces to provide a basis for decontamination and related public health protective decisions and guidance.
6. Explore and record data to determine the role human activities play in potentially generating aerosols capable of transmitting SARS CoV-2 in both enclosed and open spaces. The evidence that supports the hypothesis that aerosol transmission may be occurring in encloses spaces does not preclude the phenomenon from occurring in larger enclosed spaces (arenas, churches) or even open spaces. The above referenced choir’s incidence rates may have been affected by higher exposures, and possibly high exposure deep into the lungs due to higher inhalation rates, despite lower concentrations in aerosols that might be postulated for asymptomatic individuals. The same might be said for persons exercising. Higher air flows in open or larger spaces would have a diluting effectdepending on important factors including wind speed, humidity, and temperature.
7. In light of the current weight of evidence that aerosols can transport SARS-CoV-2, and as new evidence emerges, further explore appropriate measures to curb inhalation exposure to small aerosols, including 5 µm or less, within buildings, rooms, and surfaces where these aerosols might travel and settle.
As more detailed information becomes available, longer-term protective strategies for curbing the transmission of SARS-CoV-2 and incidence of COVD-19 can be developed. The weight of the currently available evidence warrants immediate
attention to address the significance of aerosols with important implications for public health protection.
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