Dr. David Nabarro:

To be straight and totally candid, that particular guidance is not as clear as I would ideally wish. The reason is that this is an area where there is a massive degree of disagreement. From reading the news, there is even disagreement in Ireland about this matter. One group of people says the science is not very strong and that if people are wearing masks widely it will lead to a false sense, a sense of complacency that makes them make the wrong choices. There is also some anxiety that people will get fed up of wearing masks and do it improperly, as I described earlier. On the other side there are people, and I belong to this camp, who feel that this is a proper part of an overall strategy and that it is the right thing to do, especially when people have to be closed up such as on a commuter train or a factory floor. People will become responsible about mask wearing and will do it in a way that is good, though it may take them a bit of time. I feel that way because I was working in south-east Asia in 2003 and 2004 after the SARS outbreak and I saw the role face protection had there. I have now slightly put myself on one side of this even-handed guidance from the WHO.