Scientific evidence for mask wearing

Masks and hamsters
https://www.foxnews.com/health/wearing-face-mask-reduce-coronavirus-transmission-75-percent-study-shows

https://fightcovid19.hku.hk/hku-hamster-research-shows-masks-effective-in-preventing-covid-19-transmission/

https://jamanetwork.com/journals/jama/fullarticle/2763852
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
https://www.who.int/news-room/q-a-detail/q-a-coronaviruses
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.

Видео Scientific evidence for mask wearing канала Dr. John Campbell