[russellw]

I've been reading an in-depth study from Korea about the use of masks in public transport environments and their effectiveness.

South Korea, or more specifically Seoul, has one of the highest public transportation use rates in the world (65% of all movements) and thus makes a good case study. They also have a smart card system for users that shows time/location of embarkation, carriage travelled in (on trains) and time/location of disembarkation which allowed accurate modelling of an individuals repeated mobility pattern of regularity and therefore reproducible patterns. Thus, the 'familiar stranger group', which a specific public transportation user frequently encounters was analysed and it was possible to simulate the spreading process of the COVID-19 virus in public transportation networks over a period of time.

Existing studies proved that wearing N95 masks can block almost all mock viruses and widespread use of the mask can effectively suppress aerosol propagation. KF94 and KF80 masks exhibit 98.7% and 87.6% anti-inhalation effects while the efficacy of an unauthenticated mask worn by an untrained individual is in the range of 58 to 85%.

The executive summary is thus:

1. When social distancing is implemented without mandatory mask-wearing the effect of reducing congestion can be reflected which results in a 39.8% reduction in cases.

2. When only wearing a mask is mandatory without social distancing, a 95.8% reduction is observed because of the mask-wearing, even if congestion occurs.

3. When both social distancing and mandatory mask-wearing are implemented the compounded benefits of distancing and mask-wearing result in a 96.6% reduction.