We have been repeatedly told that 'there is no evidence' wearing face masks will protect us from infection. But is that true?
For several weeks, health professionals, political leaders and even the World Health Organization have told the public that people do not need to use protective face masks unless they are sick or caring for someone with Covid-19.
Experts agree that medical-grade protective gear, such as N95 respirators, should be reserved for health workers, but officials from the US Centers for Disease Control and Prevention said they were reviewing their recommendations after new data showed nearly a quarter of those infected did not show symptoms, meaning they were infectious perhaps without realizing it.
In the UK, authorities have repeatedly said that “there is no evidence” wearing face masks will protect the public from infection.
But data from countries which enforced mandatory mask-wearing suggests they have helped curb the spread of the virus and kept death rates low.
For instance, according to at least one report: Austria has apparently managed to reverse its crisis after making masks compulsory on April 6, following a spike in infections the previous month.
In the fortnight since the rule was introduced, the nation's daily rise in positive cases dropped from 90 per million people to less than 10.
This contradicted what the United Kingdom government told its citizens. They are denying that masks are effective if used by the general public.
Indeed, Public Health England (PHE) has said that wearing a mask could spread the virus: it causes people to touch their face and increases the chances of a person acquiring the virus.
PHE added: "People also wear them for much longer than they are designed, causing them to become moist, unsanitary and an ideal environment for bugs to breed in."
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This isn't the case in the Czech Republic and Slovakia. As two of the first countries to make masks compulsory in Europe, they now enjoy a low infection rate per capita.
Sixty three Czechs per 100,000 have been infected and fewer than two per 100,000 have died from the virus. It is even lower in Slovakia. Twenty one per 100,000 people have caught the virus and just 0.2 per 100,000 have died.
In contrast, 182 out of 100,000 Britons have been infected, while 25 per 100,000 have died of Covid-19.
According to George Gao, the director-general of the Chinese Center for Disease Control and Prevention: "The big mistake in the US and Europe, in my opinion, is that people aren't wearing masks."
Gao added: "This virus is transmitted by droplets and close contact. Droplets play a very important role -- you've got to wear a mask, because when you speak, there are always droplets coming out of your mouth."
Covid-19 spreads quickly because these droplets can stay in the air.
USA Today cited a study published in the Journal of the American Medical Association, which revealed that "liquid droplets from sneezes, coughs and just exhaling can travel more than 26 feet and linger in the air for minutes."
A face mask alone does not stop the spread of the disease. According to WHO: "surgical masks do not stop people from catching coronavirus."
According to Christine Francis, a consultant from WHO's Infection Prevention and Control: "You must combine with hand hygiene and other preventive measures."
WHO adds: "Masks are effective only when used in combination with frequent hand-cleaning with alcohol-based hand rub or soap and water."
Countries have seen varying degrees of success with face masks.
Forty days since the 100th case of Covid-19, US, Italy and Spain have over 100,000 Covid-19-positive cases.
It is possible that the number of cases didn't slow down or plateau because they didn't wear masks to slow down the spread.
Meanwhile, Asian countries that enforced wearing face masks reported fewer cases. Hong Kong and Singapore have fewer than 1,000, while Japan has almost 3,000. South Korea has almost 10,000 cases, but the spread plateaued from the 15th day to the 40th.
Although China ranked fourth place at almost 100,000, the country also plateaued on the 20th day because they wore face masks.