So, @WHO has published its new interim guidance on the use of #masks in fighting the #covid19 pandemic. No shockers here, it’s mostly what @WHO has said before, so I’ll be brief. Document is here: https://www.who.int/publications-detail/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in-healthcare-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak

First of all, document reiterates what @WHO has been saying about the spread of #Covid19. That most transmission comes from symptomatic patients via droplets though they acknowledge that there is some spread from patients before symptoms.

So how does WHO see evidence of masks in community setting? 3 points.
1. there is evidence that masks can prevent spread of droplets from infected person to another person and to the environment

2. there is limited evidence that mask can protect healthy person in same household as a sick patient or in a mass gathering
3. there is no evidence at the moment in community setting that mask, "including universal community masking", can prevent healthy person being infected.

So what advice is WHO offering politicians that are considering asking all people to wear a mask?
On the plus side, WHO says it may reduce risk of pre-symptomatic patients transmitting virus and may reduce the awkwardness/stigma of wearing mask for symptomatic people.

Downsides according to WHO:
- a false sense of security that could lead to more carelessness
- danger of mask shortage for health care workers
- less ressources for more important measures
- breathing difficulties
- self-contamination by touching and reusing contaminated mask

(Seems to me that most of those risks are manageable. I.e. clear communication to public that this may not do much, produce masks in community to avoid impacting HCW supply etc. Still not clear whether this will have any significant net benefit, but worth trying.)

"Whatever approach is taken, it is important to develop a strong communication strategy to explain to the population the circumstances, criteria, and reasons for decisions.” (I wish @WHO had included point from presser that if this is done, should be accompanied by research!)

Since this was about community masking, let me just reiterate WHO guidance on other settings:

Suspected #COVID19 patients or ones with mild symptoms should “wear a medical mask as much as possible; the mask should be changed at least once daily”. Their caregivers or household contacts should “wear a medical mask when in the same room as the affected person”.