The Infectious Nature of Patient-Generated SARS-CoV-2 Aerosol

Santarpia, Joshua L.; Herrera, Vicki L.; Rivera, Danielle; Ratnesar-Shumate, Shanna; Reid, St Patrick; Denton, Paul W.; Martens, Jacob W S; Fang, Ying; Conoan, Nicholas H.; Callahan, Michael V.; Lawler, James V.; Brett-Major, David M.; Lowe, John

doi:10.1101/2020.07.13.20041632

Cited by 75 publications

(115 citation statements)

References 24 publications

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“…Different droplet sizes may emerge from, and penetrate into, different regions of the respiratory tract, and so have different c i (r); moreover, virions on relatively small droplets may diffuse to surfaces more rapidly and so exchange with bodily fluids more effectively. Such a size dependence in infectivity, c i (r), is also consistent with the recent experiments of Santarpia et al3 , who reported that replication of SARS-CoV-2 is more apparent9 -v-p) singing softly (aah-w-p) speaking (c-v-p) whispering (c-w-p)mouth breathing (b-nm) nose breathing (b-nn) Model predictions for the steady-state, droplet-radius-resolved aerosol volume fraction, s (r), produced by a single infectious person in a well-mixed room. The model accounts for the effects of ventilation, pathogen deactivation and droplet settling for several different types of respiration in the absence of facemasks (p m = 1).…”

supporting

confidence: 91%

“…pathogen responsible for COVID-19, severe-acute-respiratory-syndrome coronavirus 2 (SARS-CoV-2), is known to be transported by respiratory droplets exhaled by an infected person [3][4][5][6][7] .…”

mentioning

confidence: 99%

“…We proceed by deducing the associated infection rate from a single infected individual to a susceptible person. We illustrate how the model's epidemiological parameter, a measure of the infectiousness of COVID-19, may be estimated from available epidemiological data, including transmission rates in a number of spreading events, expiratory drop size distributions 9 and the infectivity of such droplets bearing SARS-CoV-2 3 . Our estimates for this parameter are shown to align with those recently reported 18 , but call for refinement through consideration of more such field data.…”

mentioning

confidence: 99%

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Beyond Six Feet: A Guideline to Limit Indoor Airborne Transmission of COVID-19

Bazant

Bush

2020

Preprint

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The revival of the global economy is being predicated on the Six-Foot Rule, a guideline that offers little protection from pathogen-bearing droplets sufficiently small to be continuously mixed through an indoor space. The importance of indoor, airborne transmission of COVID-19 is now widely recognized; nevertheless, no quantitative measures have been proposed to protect against it. In this article, we build upon models of airborne disease transmission in order to derive a safety guideline that would impose a precise upper bound on the cumulative exposure time, the product of the number of occupants and their time in an enclosed space. We demonstrate the manner in which this bound depends on the ventilation rate and dimensions of the room; the breathing rate, respiratory activity and face-mask use of its occupants; and the infectiousness of the respiratory aerosols, a disease-specific parameter that we estimate from available data. Case studies are presented, implications for contact tracing considered, and appropriate caveats enumerated.

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supporting

confidence: 91%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Beyond Six Feet: A Guideline to Limit Indoor Airborne Transmission of COVID-19

Bazant

Bush

2020

Preprint

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“…For primary schools we considered only the RA allocation. SARS-CoV-2 could be transmitted in households, classrooms or in common areas of the school, all of which were treated as homogeneously mixing on account of evidence for aerosolized routes of transmission 18 . Individuals were also subject to a constant background risk of infection from other sources, such as shopping centers.…”

Section: Model Overviewmentioning

confidence: 99%

Model-based projections for COVID-19 outbreak size and student-days lost to closure in Ontario childcare centers and primary schools

Phillips

Browne

Anand

et al. 2020

Preprint

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The disruption of professional childcare has emerged as a substantial collateral consequence of the public health precautions related to COVID-19. Increasingly, it is becoming clear that childcare centers must be (at least partially) operational in order to further mitigate the socially debilitating challenges related to pandemic induced closures. However, proposals to safely reopen childcare while limiting COVID-19 outbreaks remain understudied, and there is a pressing need for evidence-based scrutiny of the plans that are being proposed. Thus, in order to support safe childcare reopening procedures, the present study employed an agent-based modeling approach to generate predictions surrounding risk of COVID-19 infection and student-days lost within a hypothetical childcare center hosting 50 children and educators. Based on existing proposals for childcare and school reopening in Ontario, Canada, six distinct room configurations were evaluated that varied in terms of child-to-educator ratio (15:2, 8:2, 7:3), and family clustering (siblings together vs. random assignment). The results for the 15:2 random assignment configuration are relevant to early childhood education in Ontario primary schools, which require two educators per classroom. High versus low transmission rates were also contrasted, keeping with the putative benefit of infection control measures within centers, yielding a total of 12 distinct scenarios. Simulations revealed that the 7:3 siblings together configuration demonstrated the lowest risk, whereas centres hosting classrooms with more children (15:2) experienced 3 to 5 times as many COVID-19 cases. Across scenarios, having less students per class and grouping siblings together almost always results in significantly lower peaks for number of active infected and infectious cases in the institution. Importantly, the total student-days lost to classroom closure were between 5 and 8 times higher in the 15:2 ratios than for 8:2 or 7:3. These results suggest that current proposals for childcare reopening could be enhanced for safety by considering lower ratios and sibling groupings.

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“…Convincing policy makers of the risk from short-range aerosol is reliant upon super spreading events and in vitro work with surrogates. Yet history tells us that virus-laden particles in the air spread infection and confirming this is probably only a matter of time [14,15,17]. There are good reasons why we should wear masks in contained indoor venues and wear them correctly.…”

mentioning

confidence: 99%