A simple model to show the relative risk of viral aerosol infection and the benefit of wearing masks in different settings with implications for Covid-19 .

Barr, G. D.

Background . Widespread use of masks in the general population is being used in many countries for Covid-19 . There has been reluctance on the part of the WHO and some governments to recommend this . Methodology . A basic model has been constructed to show the relative risk of aerosol from normal breathing in various situations together with the benefit from use of masks which is multiplicative . Results . Social distancing at 2 metres is validated but in confined areas is time limited and the use of masks in the absence of extremely good ventilation is important. Where social distancing is not possible at all times or an infectious person is in a confined area for a prolonged period there is a higher risk of infection requiring protection . Conclusions . The use of masks should be factored into models and used at an early stage as widespread use of more efficient masks could have a large impact on control and spread of infection . Public health planning requires stockpiling masks and encouraging everyone to have suitable masks in their household when supplies are normalised . The use of a cloth mask will be better than no protection at all .