I received this circular to all staff from Great Ormond St hospital today. 73 out of 181 staff have tested positive and 318 staff members off sick. (THREAD 1)

An informant tells me "social distancing in the hospital is a fiction. Whatever the inadequacies of PPE for patient contact my concern is about the use of masks in non-clinical hospital areas. Many team members do handovers in a small office space without the use of masks.” (2)

" I appreciate the ‘science’ isn’t clear but Korean virologist Professor Kim (leader of S Korea test programme) is incredulous that we’re not using masks. Also by seeing our consultant respiratory paediatrician walking down the street wearing a mask!" (3)

"Nurses, doctors, admin, cleaners are expressly discouraged from wearing masks around the hospital. Is our cultural reluctance to wear masks an error? Staff will be happy to bring their own masks from the chemist if given permission.” (4)

So what is the evidence? The Oxford review group suggest that standard masks are probably as effective as respirator masks. Six trials in China for other respiratory viruses showed no significant difference between the two. (5)

What about masks v non masks for people not attending patients directly? The US/Europe view is summarised as:
1. No scientific evidence masks reduce the risk of transmission
2. Might result in those wearing masks to relax other distancing efforts with a sense of protection (6)

3. Must preserve masks for at-risk healthcare workers. http://www.cidrap.umn.edu/news-perspective/2020/04/commentary-masks-all-covid-19-not-based-sound-data (7)

BUT An excellent review article says the evidence on masks may change as more and more people are infected, eg in hospitals. Early in the infection people are shedding the virus without symptoms. (8)
https://www.forbes.com/sites/tarahaelle/2020/04/01/should-everyone-wear-a-mask-in-public-maybe-but-its-complicated/#5d658c25a02f

China and Korean colleagues say everyone should wear a mask in hospitals and cannot understand our policies. I hear that WHO might be updating their policy soon as the epidemic intensifies and risks change. (9)