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Letters Transmission of SARS-CoV-2

Quantifying transmission risk of SARS-CoV-2 in different situations

BMJ 2022; 376 doi: (Published 20 January 2022) Cite this as: BMJ 2022;376:o106
  1. T Greenhalgh, professor of primary care health sciences1,
  2. Zhe Peng, research scientist2,
  3. Jose L Jimenez, distinguished professor2,
  4. W Bahnfleth, professor of architectural engineering3,
  5. S J Dancer, consultant microbiologist45,
  6. L Bourouiba, professor of civil and environmental engineering6
  7. On behalf of the 22 authors of the technical paper in Environmental Science and Technology
  1. 1Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford OX2 6GG, UK
  2. 2Department of Chemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
  3. 3Department of Architectural Engineering, Pennsylvania State University, University Park, PA 16802, USA
  4. 4Department of Microbiology, NHS Lanarkshire, Glasgow, UK
  5. 5School of Applied Sciences, Edinburgh Napier University, Edinburgh, UK
  6. 6Fluid Dynamics of Disease Transmission Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
  1. trish.greenhalgh{at}

SARS-CoV-2 is transmitted mainly through short and long range airborne transmission.12 The omicron variant shows faster transmission and greater vaccine escape than previous variants.3 Further measures are needed to contain transmission.

In 2020 we argued in The BMJ that “rigid safe distancing rules are an oversimplification based on outdated science.”4 We produced risk charts for SARS-CoV-2 transmission incorporating multiple variables: indoors versus outdoors (and level of ventilation if indoors), room occupancy (low or high), time spent together (short or long), vocalisation …

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