(We should understand the relatively small amount of protection a mask provides.)

Do face masks work against the coronavirus and should you wear one?

As cases of covid-19 continue to rise, many people are choosing to wear a face mask when out in public – but do they work?

Guidance on face masks varies wildly among international health bodies and governments. The World Health Organization (WHO) currently only recommends face masks for people who are coughing or sneezing, or for those who are caring for people who are suspected to have covid-19.

https://www.newscientist.com/article/2240288-do-face-masks-work-against-the-coronavirus-and-should-you-wear-one/

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Facemasks and similar barriers to prevent respiratory illness such as COVID-19: A rapid systematic review

The evidence is not sufficiently strong to support widespread use of facemasks as a protective measure against COVID-19. However, there is enough evidence to support the use of facemasks for short periods of time by particularly vulnerable individuals when in transient higher risk situations. Further high quality trials are needed to assess when wearing a facemask in the community is most likely to be protective.

https://www.medrxiv.org/content/10.1101/2020.04.01.20049528v1