Thread by @DearPandemic

1/ Q: Will the 6 feet/2 meter rule keep me safe indoors?

A: Not by itself.
Important additional considerations include:
⭐️ Ventilation
⭐️ Number of people in the room
⭐️ Duration of contact
⭐️ Type of activity (silent, speaking, shouting/singing)
⭐️ Use of masks

2/ Why are these additional precautions needed? Don’t airborne droplets fall to the ground within this distance?
The history of the 6ft/2m distancing rule began over 100 years ago with the study of how droplets were emitted during speech, coughing, and sneezing.

3/ In early studies most (but not all) large droplets were found to fall within 1-2 meters, gradually entrenching the idea of the 2m rule.

More recent evidence has shown projection of large respiratory droplets from coughs and sneezes well beyond 2 meters.

4/ While large droplets typically drop within 1-2 meters (3-6 ft), smaller droplets or “aerosols” are light & thus can travel greater distances and accumulate in poorly ventilated rooms.

5/ Importantly for SARS-CoV-2, asymptomatic & pre-symptomatic spread is common, implying a more important role for smaller particles exhaled during talking & breathing rather than coughing or sneezing.

6/ Forced exhalation such as singing can generate higher momentum clouds of exhaled air, which can stay more concentrated & travel up to 7-8 meters (23-26 ft).

7/ These risks can compound in crowded, noisy indoor environments (with loud talking/shouting) such as meatpacking plants & bars & restaurants.
Respiratory droplets & aerosols are much more quickly diluted outdoors, the basis of encouraging outdoor activities wherever possible.

8/ The attached chart provides a framework for assessing the interaction of these risk factors. Note this is a “qualitative” figure in that it is not based on a model with specific numbers & probabilities of risk, but is meant to provide a general guide to decision making.

9/ BOTTOM LINE: Risks are complex & interacting.

In the highest risk situations (indoors w/poor ventilation, high numbers of people, prolonged duration of contact), it’s important to physical distance beyond 2m/6 ft, minimizing the time of exposure, and use face masks.

Link to full BMJ article for figure authored by @trishgreenhalgh @DrZeshanQureshi @drnrjones

bmj.com/content/370/bm…

& excellent coverage of current knowledge about aerosol transmission from @jljcolorado
time.com/5883081/covid-…
& quites from @linseymarr & @j_g_allen
undark.org/2020/08/26/cov…

Finally Practical info about ventilation from @ShellyMBoulder: bit.ly/34TIdDZ

Y una traducción en español también!