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From page 148... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief Proceedings of a Workshop IN BRIEF October 2020 AIRBORNE TRANSMISSION OF SARS-CoV-2 Proceedings of a Workshop -- in Brief INTRODUCTION AND WORKSHOP OBJECTIVES With the rapidly evolving coronavirus disease 2019 (COVID-19) pandemic, researchers are racing to find answers to critical questions about the virus that causes the disease severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Read the entire page →
From page 149... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief BOX 1 Workshop Statement of Task The science around transmission of SARS-CoV-2, the virus that causes COVID-19, is complex and evolving quickly. For example, questions about how long infectious particles linger in the air and how far they travel have been the subject of debate because of the implications for interventions. Read the entire page →
From page 150... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief • Source control: Source control can greatly reduce, if not completely eliminate, the number of aerosols released into the air • Ventilation/filtration: With effective ventilation/filtration, the number of viral aerosols can be greatly reduced • Distance and personal protective equipment: These interventions can offer some protection by reducing a person's exposure • Hygiene: Research indicates that the highest viral loads or positive samples can be found on the floor. Cleaning the floor can reduce the possibility of resuspension FIGURE 2 Interventions to reduce the spread of SARS-CoV-2. Read the entire page →
From page 151... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief opening comments on the epidemiologic triangle (see Figure 3) , there are a number of environmental and other variables (continuous exposures during the infectious period, a lack of protective measures like face coverings, and air characteristics) Read the entire page →
From page 152... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief As Marr notes, there has been widespread conception that aerosols and droplets >5 µm settle within about 6 feet of the infected person generating them due to gravity. However, the use of 5 µm as a cutoff for these definitions is not supported by modern aerosol science, stated Marr, and has hampered the understanding of the transmission by creating a false dichotomy between what is considered a droplet and what is considered an aerosol. Read the entire page →
From page 153... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief FIGURE 4 Droplets versus aerosols during coughing and talking. Aerosols dominate as the distance from the source increases, for both coughing and talking related exposure. Read the entire page →
From page 154... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief Definitively proving the aerosol transmission pathway is challenging and will require more research, according to Milton and William Lindsley, National Institute for Occupational Safety and Health. In particular, Milton and Lindsley noted that methods that can sample different sizes and large volumes of air while not damaging the virus are needed. Read the entire page →
From page 155... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief During the discussion, panelists identified challenges in studying and understanding the dose required for infection, the topic of Critical Question 4 below. Milton noted that in experimental studies done in the 1960s on influenza, the infectious dose was far lower via aerosols than drops. Read the entire page →
From page 156... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief local turbulence, and posture (Liu et al. Read the entire page →
From page 157... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief Miller noted that research is needed to determine what ventilation rates are warranted for airborne infectious disease control. Another challenge will be to develop energy-efficient and cost-effective technologies and strategies that also provide high ventilation rates as current practices to minimize energy use are not conducive to high ventilation. Read the entire page →
From page 158... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief During the open discussion, the speakers and panelists commented on racial and socioeconomic disparities in COVID-19 infections, and how that might be connected to the built environment. Nazaroff noted that Hispanics in Alameda County, California, are getting sick with COVID-19 seven times more than non-Hispanic Whites in the same area. Read the entire page →
From page 159... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief proximity was a more efficient mode of transmission (Halfmann et al. 2020; Richard et al. Read the entire page →
From page 160... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief To more fully understand conditions that may increase the risk of transmission, Lakdawala said, more research is needed to define the human infectious dose range, differences in infectivity by aerosol particle size, and impact of external factors on disease severity. Yen emphasized the need to know how dose and route of inoculation impact onward transmission; to know the size distribution of virus-laden aerosols in exhaled breath; and to know the size range of aerosols that mediate transmission. Read the entire page →
From page 161... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief FIGURE 9 SEIR model with the workshop's critical questions. This diagram provides a broader framework for considering the course of the SARS-CoV-2 epidemic in the population. Read the entire page →
From page 162... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief Risk of exposure to COVID-19 in commercial flight situations was discussed by John "Jack" McCarthy, Environmental Health & Engineering, Inc., who consults for the health care and airline industries and a number of other organizations. He noted that while there are high ventilation rates in aircraft cabins, up to 30 air changes per hour, a key challenge is addressing travel-associated behaviors that may increase risk, such as crowding when exiting the plane. Read the entire page →
From page 163... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief Fisher, K.A., M.W. Tenforde, L.R. Read the entire page →
From page 164... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief Nicas, M., W.W. Nazaroff, and A Read the entire page →
From page 165... ... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief DISCLAIMER: This Proceedings of a Workshop -- in Brief was prepared by Marilee Shelton-Davenport, Julie Pavlin, Jennifer Saunders, and Amanda Staudt as a factual summary of what occurred at the workshop. The statements made are those of the rapporteurs or individual workshop participants and do not necessarily represent the views of all workshop participants; the planning committee; or the National Academies of Sciences, Engineering, and Medicine. Read the entire page →

From page 148...

... Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop -- in Brief Proceedings of a Workshop IN BRIEF October 2020 AIRBORNE TRANSMISSION OF SARS-CoV-2 Proceedings of a Workshop -- in Brief INTRODUCTION AND WORKSHOP OBJECTIVES With the rapidly evolving coronavirus disease 2019 (COVID-19) pandemic, researchers are racing to find answers to critical questions about the virus that causes the disease severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)