That position was adopted by countries such as the United States, Britain, much of Europe, Australia, New Zealand, India, South Africa and Singapore
Having told their populations that wearing masks was all but useless against the coronavirus, several Western countries have performed dramatic U-turns in the last few days.
The rapid rethink as the number of deaths has rocketed has stirred anger and confusion, with some accusing their leaders of lying to them.
The most spectacular about-turn has been in the United States where President Donald Trump on Friday urged all Americans to wear a mask when they leave home.
While mask wearing has been widespread in Asia since the beginning of the epidemic, the World Health Organization (WHO) and numerous governments have insisted that they should only be worn by carers.
That position was adopted by countries such as the United States, Britain, much of Europe, Australia, New Zealand, India, South Africa and Singapore.
“There is no specific evidence to suggest that the wearing of masks by the mass population has any potential benefit,” said Dr Mike Ryan, executive director of WHO’s health emergencies program, last week.
All that changed this week. The WHO made a U-turn itself, with Ryan saying: “We can certainly see circumstances on which the use of masks, both home-made and cloth masks, at the community level may help with an overall comprehensive response to this disease.”
Prompting the change was growing evidence that some people infected with the coronavirus do not show symptoms and are able to make others sick.
Seen from Asia, where wearing masks during the flu season is normal, Western reluctance seemed utterly baffling.
Singapore, which had been steadfast in telling its citizens not to wear masks if they were not unwell, changed its stance as its confirmed cases crossed the 1,000 mark, with six deaths by Saturday morning, and will start distributing reusable masks to all households from Sunday.
There is a "definite shift in the position of the US" towards wearing masks, Professor KK Cheng, a public health specialist at Birmingham University in Britain, told AFP.
The expert, a strong advocate of their use, said the WHO was reviewing its guidance.
"The big mistake in the US and Europe is that people aren't wearing masks," George Gao, the head of the China Centre for Disease Control, told the journal Science.
Experts agree that surgical masks are not a foolproof way to prevent coronavirus infection.
But people infected with the virus are advised to wear them to stop the spread to others, with evidence that transmission can happen before a person knows they are sick.
Another argument in their favour is the theory -- not yet scientifically proven -- that the virus can be transmitted through the air.
'Spread through speaking'
Dr Anthony Fauci, who is leading the US government's response, has backed research that found it can be suspended in ultrafine mist formed when people exhale.
Research indicates "the virus can actually be spread even when people just speak as opposed to coughing and sneezing," Fauci told Fox News.
If that is confirmed, it would explain why the virus so contagious.
Even before the White House recommended masks, Bill de Blasio, the mayor of New York, which has been badly hit by the epidemic, said residents should cover their faces when they got out.
"That could be a scarf or something you make yourself, a bandana," he said.
Germany's disease control agency, the Robert Koch Institute, also urged Germans to wear homemade masks as many people across Europe and North America turned to online DIY tutorials posted by medical experts.
Koch Institute head Lothar Wieler said masks "could help to protect others, but they don't help protect the wearer themselves.
"That is very important to understand," he added, a message repeated by Professor Cheng.
"You wear a mask to reduce droplets from one's own respiratory tract. It only works if everyone wears them, and if everyone does, you only need a very basic mask.
"A piece of tissue can block it. It's not perfect, but it's much better than nothing," he told AFP.