Professor Philip Nolan:

Yes. I wish to make a point relating to the discussion about face masks, distance and surfaces. All of that work is based on understanding how droplets transmit. We know that the virus lives here for a while and can be transmitted over a certain distance. What we do not know is how likely that is then to lead to infection. Simply because the virus is there does not mean it is going to infect a person. Part of the reason for the uncertainty around 1 m versus 2 m, or face masks versus no face masks, is that even though we have evidence about what they do to droplets, we have very limited evidence about what they do to a person's actual chances of catching the virus. That is why there is a constant erring on the side of caution; it is not necessarily erring but if one is going to make a mistake, one needs to make it on the side of caution and not on the side of liberty.