Thread by @KKCheng4

Issues on masks that the WHO should clarify.There's evidence on benefits for both source control (reducing droplet spread) and self protection. As surgical masks must be reserved for HCWs, #clothmasks could be the answer.
#COVID19 @news_ub @unibirmingham
go.shr.lc/38M5GVz

Cloth masks are inferior to surgical masks but might reduce the R0 enough to ease the epidemic IF everyone wears one in crowded places (eg crowded trains). It could reduce transmissions by asymptomatic shedders in the community. A non immune form of "herd protection" (@gauden)

There's laboratory evidence on cloth masks but no community trials. However, this is much cheaper and more sustainable than major social distancing (also untested). DIY may do but the global garment industry could probably make 100m+ a day soon if asked. Washable and reusable.

People who panic buy masks seem also to be after hand gel etc. So mask wearing may not clash with hand hygiene. Benefits for each individual are probably small but population impact may be meaningful (like wearing seat belts) - prevention paradox.

Please remember: 1. Surgical masks must be reserved for HCWs; 2. Cloth masks do not replace hand hygiene and sensible social distancing; 3.Wash hands before putting on and taking off a mask. Avoid touching the front of the mask.

@WHO @DrTedros , health ministers: If cloth masks are available, does the balance of evidence suggest that there's a reasonable chance that mass masking could bring overall benefit and would be a useful additional intervention? Cheaper and more sustainable than other measures.

Critics say that wearing mask could give false sense of security. There's no good empirical evidence of that. One could also hypothesise that wearing a mask would↑overall awareness for prevention. Find me someone panic buying masks who doesn't go for hand gel as well.@alanmcn1

As asymptomatic “virus shedders” may be fuelling community transmissions, widespread wearing of cloth masks could be an effective method of source control. A moderate↓of R0 could save the day for our besieged hospitals. @ICS_updates @NHSuk

Imagine this: A and B each takes a cloth mask & face each other 0.5m apart. Before putting it on, A coughs directly towards B. Then A puts on the mask & coughs. Then both put on the mask & cough. Tell me if there are likely to be differences.

If this happens in a crowded train.