Scientific evidence for mask wearing
May 22, 2020
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Dr John Campbell Episodes Around May 22, 2020
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22:04Now PlayingScientific evidence for mask wearing
YouTube Description
as posted by the channelMasks and hamsters
Hong Kong
Rate transmission through respiratory droplets or airborne particles dropped up to 75% using masks.
Public mask wearing effectiveness, huge,” (Dr. Yuen Kwok-yung)
Transmission can be reduced by 50 percent, especially when masks are worn by infected people
Universal masking = 80% will significantly flatten the curve
Linda Bourouiba JAMA
Sneeze (10-30 m/s), 7 – 8 m or 23-26 feet
Cough 5 - 6 metres or 19 feet,
Breath 2 metres or 7 feet
Masks, droplets come out of the side, reduces range
Background
Dichotomous classification between large vs small droplets, or droplets vs aerosol
Arbitrary droplet diameter cutoffs, from 5 to 10 μm
Host-to-host transmission as droplets or aerosol routes
Rapid international spread of COVID-19, using arbitrary droplet size cutoffs may not be accurate
Possibly contributing to the ineffectiveness of some procedures used to limit the spread of respiratory disease.
Recent work
Exhalations, sneezes, and coughs, mucosalivary droplets
Multiphase turbulent gas cloud
Continuum of droplet sizes
Droplets can survive for minutes in clouds
Payload of pathogen-bearing droplets
A hot and moist gas cloud
Ambient environment (temperature, humidity, and airflow)
Residues or droplet nuclei that may stay suspended in the air for hours
Ambient environment (temperature, humidity, and airflow).
China (2020), COVID-19 found in ventilation systems in hospital rooms of infected patients
Implications
World Health Organization recommendations 3-foot (1-m)
Centers for Disease Control, 6-foot (2-m) separation.
May underestimate the distance
Mask efficacy as source control depends on the ability of the mask to trap or alter the high-momentum gas cloud emission with its pathogenic payload.
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