I think he is slightly over egging the pudding. My calculation suggest on the simple inverse cube that doubling the distance makes at least an 8 fold reduction...and I gave you all the benefit of my calculations. If the spray is gravity driven,then it becomes even more distance friendly..and multiply by.An inverse exponential reduction .. exp(-x/z).. with Z the horizontal distance a spray travels from nose to ground, X the distance apart.Masks, again...
Vallance said evidence in favour of masks protecting public 'marginal but positive'
Back in the health committee Vallance is now talking about masks.
He says the evidence suggests that, in terms of preventing wearers from spreading coronavirus to others, the evidence in favour of masks or face coverings is “marginal but positive”.
In healthcare settings there is a strong case for masks, he says.
He says when people are outdoors, the risk is generally low.
But he says there are circumstances in which masks can be useful. He says the risk of infection at one metre away from an infected source is 10 to 30 times higher than at two metres.
Surely the really obvious thing to do is mandate them for people who come into contact with lots of people, and advise them for most of the rest of us?
For example, the meeter/greeter/security people in supermarkets - ducking and diving round all the incoming and outgoing customers. Indeed, in general, staff have interactions with many people even at two metres.
A single hairdresser might manage, what, six people in a day? A till operator might manage that every five minutes. If the person is extremely infectious, and we know of historical super-spreaders of various diseases, the effect of a mask on the propagation by one checkout person could be huge.
The predictor of infection is the intensity of virus flux times the duration of contact,so your hairdresser being around a person for 20 minutes and separated by 20 cm is more dangerous than a meet and greeter with 1000 people at 10 seconds at 2 metres , and maybe 100 infected.
For my part, should I need to spend time indoors in confined spaces with strangers or on public transport, I will want a mask.