Airborne Transmission of SARS-CoV-2 Proceedings of a Workshop—in Brief (2020) / Chapter Skim
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Airborne Transmission of SARS-CoV-2: Proceedings of a Workshopin Brief
Airborne Transmission of SARS-CoV-2: Proceedings of a Workshopin Brief
Pages 1-18
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around these four critical questions: 1. What size aerosol particles and droplets are generated by people and how do they spread in air?
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IMPORTANCE OF UNDERSTANDING AIRBORNE TRANSMISSION: LESSONS FROM THE FIELD Anthony Fauci, National Institute of Allergy and Infectious Diseases; Jay Butler, Centers for Disease Control and Prevention (CDC) ; Jonathan Samet, Colorado School of Public Health; and Linsey Marr, Virginia Tech, provided an overview of why it is important to understand airborne transmission for SARS-CoV-2, including what is known based on epidemiologic and outbreak data.
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agile in our views as additional data become available because airborne spread of SARS-CoV-2 is also plausible, and our approaches need to be data based and not dogma based." Epidemiologic Studies of Transmission of SARS-CoV-2 Epidemiologic patterns inform experts' understanding of SARS-CoV-2 transmission. Butler provided an overview of current epidemiologic research, which has indicated that outbreaks of COVID-19 resulting from a point source (one infected person transmitting to others)
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The agent, or microbe, situation and enable communication among experts with different technical causes disease; the host, or organism, backgrounds. Transmission of respiratory viruses can occur through direct harbors disease; and the environment, or person-to-person contact, indirect contact, large droplet spray, aerosols, or external factors, causes or allows disease transmission.
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Importantly, despite its lack of grounding in science, this dichotomy has guided decision-making about controlling transmission, for example, underpinning guidance around infectious disease control in hospitals. The exposure path of the virus is critical to understanding transmission, stated Marr.
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Resuspension of virus-containing dust or aerosol particles that have settled on the floor, clothing, or other surfaces, as well as aerosolization of fomites, could be another transmission pathway, said Ristenpart, noting up to half of the aerosols in a room may be attributed to resuspension by walking on floors. Rubbing a contaminated tissue has been shown to create thousands of aerosol particles, and guinea pigs have been shown to transmit viruses via their fur (Asadi et al.
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CRITICAL QUESTION 2: WHICH SIZE DROPLETS AND AEROSOL PARTICLES ARE INFECTIOUS AND FOR HOW LONG? This session addressed factors that influence the infectivity and transport of SARS-CoV-2, including which size droplets and aerosol particles may be infectious, and for how long.
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CRITICAL QUESTION 3: WHAT BEHAVIORAL AND ENVIRONMENTAL FACTORS DETERMINE PERSONAL EXPOSURE TO AIRBORNE SARS-COV-2? This session addressed a range of factors that affect how much individuals are exposed to SARS-CoV-2.
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and 6.7 L/s per person for school classrooms. A study of college dormitories found that ventilation rates of <5 L/s per person may be impacting acute respiratory infections (Zhu et al.
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Air Change Rate is a measure of the outside air volume added to a space divided by the volume of that space. High Efficiency Particulate Air filters are a type of mechanical air filter that can theoretically remove at leasta 99.97% of dust, pollen, mold, bacteria, and aerosol particles.
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. Factors that impact the infectious dose are important, and Lakdawala discussed the difference between droplets and aerosols, where with influenza, it was found that small micron-sized aerosol particles required a far lower dose to cause infection than did large droplets (Alford et al.
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In her synthesis, Lakdawala noted the importance of aerosols in SARS-CoV-2 transmission, which is bolstered by animal models, with severity of disease linked to the infectious dose and influenced by genetic factors including sex, age, and underlying health status. These issues are supported by the following evidence: • Animals infected with SARS-CoV-2 can release virus-laden aerosols that can infect susceptible recipients.
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Menachery called for the development of an infection approach that resembles naturally occurring infections. For disease severity, more studies are needed on combinations of underlying health issues, age, sex, and other genetic factors.
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IMPLICATIONS FOR DISEASE CONTROL Patrick Breysse, CDC, moderated a panel focused on the implications of workshop discussions on the airborne transmission of SARS-CoV-2 in guiding public health efforts to reduce the spread of the virus. Panelists with a range of practical expertise, including a state public health official, a public health association leader, an environmental consultant, and a chief of infectious disease at a hospital, discussed their perspectives on these issues.
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CONCLUDING THOUGHTS Throughout the 2-day workshop, participants discussed critical questions around the airborne transmission of SARS-CoV-2. In his closing remarks, Samet concluded that numerous speakers and panelists discussed evidence indicating people are a source of infectious materials emitted into the air.
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Emerging Infectious Diseases 26:2276–2278. Memoli, M.J., P.A.
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2020. Air, surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
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Other National Academies entities that contributed to this workshop include the Health and Medicine Division's Board on Global Health, Forum on Microbial Threats, Board on Health Sciences Policy, Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats, and Board on Population Health and Public Health Practice; the Division on Earth and Life Studies' Board on Atmospheric Sciences and Climate, Board on Life Sciences, and Board on Environmental Studies and Toxicology; the Division on Engineering and Physical Sciences' Board on Infrastructure and the Constructed Environment; and the National Academy of Engineering's program office. Workshop planning committee members are Jonathan M
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