In relation to SARS-CoVid-2 a theoretical gold standard of face mask use is discussed and a similar principle for lockdown. The use of face masks in the general population is debated in relation to the UK public health advice that face masks are not needed in the general population. There is substantial evidence of ability of SARS-CoVid-2 to spread by aerosol which makes the UK Government's public health advice and indeed that of the WHO, that social distancing and hand hygiene alone are

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... d in the general population questionable. The question is not should the general public have mask protection but what degree of mask protection is needed? There is a shortage of suitable masks for health care workers in the UK but the need for this demand is driven by the large numbers of infected people in the community. Once the public health advice is adjusted polititians can start to try and solve the enormous logistical problem of protecting the public.