In the UK, wearing a mask or other face covering will be compulsory in shops and supermarkets in addition to public transport. In the US and around the world, many private businesses have also enforced this rule. But what is the science behind wearing a mask, and does it limit the spread of coronavirus?
Masks aren't really there to protect yourself: rather, they're very effective at preventing the spread of coronavirus when being worn by an infected individual, which is why the infection rate drops so rapidly when everyone complies and masks up.
Coronavirus is spread through respiratory droplets, which are projected outwards through speaking, coughing or sneezing. An experiment from the New England Journal of Medicine sought to check how many droplets are actually spread via speech, both with and without a mask.
The researchers used laser-mapping technology to highlight the spread of droplets. In the video below, you see the bright green splatters of droplets spread during normal speaking, then you see the same phrase being spoken while a mask.
In this experiment, investigators used a laser in a darkened box to visualize approximately 300 droplets that were generated during speech. #COVID19 #SARSCoV2 pic.twitter.com/bLaX9ORDT9April 23, 2020
Note how fewer droplets there are when the mask is worn. When both participants in a conversation are wearing masks, the chance of infection is greatly reduced because droplets aren't spreading from either participant. Wouldn't you want anyone chatting to you to prevent potentially harmful droplets from landing on you?
One study published in PNAS: The Proceedings of the National Academy of Sciences of the USA showed mask-wearing alone significantly lowered the number of infections by over 78,000 in Italy. The evidence is clear: masks help reduce the rate of infection.
Until a coronavirus vaccine is readily available, it's time to mask up.
However, although masks are now compulsory wearing in shops and supermarkets in the UK, they're not mandatory in pubs and gyms, where the risk of infection is arguably greater. The science behind this is unclear.