Dr Julian Tang, a Consultant Virologist at Leicester Royal Infirmary, has worked for many years on the transmission of corona viruses (including Influenza, Mers, Sars and Covid-19). He points out that the main route of transmission of such viruses is via tiny droplets that infected people breathe out or expel whilst talking or singing (https://www.thesun.co.uk/news/11708729/video-shows-spread-coronavirus-droplets-infected-tube/). The viruses, in such droplets, remain viable for several hours and can be directly inhaled by people nearby. The droplets may even be spread more widely by air-conditioning systems in, for example, planes and offices. This mode of infection, seems to Dr Tang, much more important than the coughing of larger droplets. These can land on surfaces, where they can be later picked up on people's hands (before being rubbed on the face where they infect). He consequently feels that hand washing (whilst useful), gives less protection against infection than avoiding (or at least limiting exposure to) the droplet 'clouds' generated by infected people. If what he says is correct (and I find it convincing), we might well see a serious resurgence of Covid-19 infections as pubs open (and people chat at tables), workers return to shared spaces and travel on planes, the tube and trains increases. Dr Tang seems to think that the relatively lukewarm advocating of face masks by the World Health Organisation more reflects a worry about getting such equipment to people in less developed parts of the world rather than concerns about the efficacy of these devices. I think I will give the pub crawl a miss for now and continue to wear a mask when near to people.
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