Countries are strengthening their rules for wearing face masks. Soon you may also have to use them outdoors

This is how the coronavirus masks protect us 3:43

London (CNN) - Coronavirus cases are advancing in parts of Europe, the process of lifting confinement orders is halting in the UK, and in America they are still struggling to contain large covid-19 outbreaks.

But as the tremors of a possible second wave of infections begin to be felt, some governments are looking for a new tool that many public health experts have been promoting for months: tighter mask mandates.

In recent days, masks have become mandatory in all public spaces, indoors or outdoors, in Madrid, Greece, the Madeira Islands of Portugal and Hong Kong.

These measures apparently contradict the long-standing understanding that covid-19 is more dangerous indoors. The British government, among others, used its first steps after confinement to encourage people to gather outdoors; Parks, beaches and natural sites around the world have been flooded by visitors during the pandemic.

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But the reasoning behind the decisions is simpler than that: After months of mixed messages from health authorities about facial covers, governments are choosing general rules to help make wearing masks a cultural norm.

"There has been a lot of confusion about where people should wear masks, and where there is confusion, people just go offline and don't wear them," Melinda Mills, director of the Leverhulme Center for Demographic Sciences at the University of Oxford, told CNN. "That is why (some countries) are moving towards a broad and general policy.

"I lean towards clarity in public messages, and in many countries, I think it has been a disaster," he added.

What we know now about the masks

The science behind airborne transmission of covid-19 is growing, but experts still agree that the risk is often higher indoors.

Earlier this month, a group of 239 scientists wrote an open letter to the World Health Organization, asking for better recognition of the potential for airborne coronavirus transmission. "A lot of people crowded together in closed places where there is little ventilation, that's what drives the pandemic," a co-organizer of the letter and professor of environmental health told CNN at the time. But the outdoors is not free from covid, and universal mandates on masking are likely to reduce spread in many types of environments.

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Researchers reported Monday that communities that ordered the use of face masks in public saw a continuous decrease in the spread of the coronavirus, but it takes some time.

Once the mandates were in place for approximately three weeks, the daily growth rate slowed by approximately 2% on average, researchers reported in the journal Health Affairs.

Their estimates suggest that these percentage declines could add up. They estimate that between 230,000 and 450,000 cases of covid-19 could have been prevented by May 22 through mandated masks.

Other scientists agree that there may be a significant risk of transmission outdoors.

"There is open air, so the risk is generally slightly less, but it is also spreading outdoors," said Abrar Chughtai, an epidemiologist at the University of New South Wales. "Whenever you can't maintain social distance, you should wear a mask."

"It is very low risk in an environment like a park or a large open space where there are not many people," added Richard Stutt of the University of Cambridge in England, who modeled the impact of wearing masks to curb the transmission of covid. -19.

“But if you walk down a busy street, there is great potential for spread there, and defining exactly what constitutes a high-risk outdoor space versus a low-risk outdoor space would be very difficult to do.

"Also, there is the complication that if people constantly take the mask off and put it back on, they risk contaminating their hands and passing it on to others," said Stutt.

That scientific knowledge is a stricter factor in mask mandates, which are also beginning to appear in countries like the United Kingdom.

But there is also a sociological element at stake, and it is simple: the mask rules are working and governments go beyond what they expected.

"There were some countries that resisted, thinking that the public would rebel (against orders to wear masks), but the public just doesn't want to be quarantined anymore," Mills said. "Governments will be emboldened a little by expanding their policies if they think this is effective."

Many researchers are surprised at how effective orders to wear masks have been. In April, an alarmingly low proportion of Britons wore masks, just 19%, according to a Kings College study published Thursday. But 70% of Britons now say they have used one in the past few weeks, according to the same study.

"People have quickly convinced themselves that they do help," Bobby Duffy, director of the King's Policy Institute and leader of the study, told CNN. "There is a very, very high level of belief in its effectiveness, which in itself is quite remarkable given how quickly the advice has changed."

That change is particularly noticeable in a country where government attempts to ease restrictions have been criticized as vague and confusing. A study by University College London last week found that only 45% of Britons feel they understand current government rules.

The same has been true in other parts of Europe; In heavily affected places like Italy and Spain, the use of masks became a cultural norm almost immediately, and studies indicate that even in the United States, where a culture war has erupted over the use of facial coatings, adherence is generally very high.

"You can bring these rules and people will follow them," said Duffy. “It is incredible how quickly people get used to things. You can also see that in the blocking measures; There was incredible support for getting into the block, even when a couple of weeks (before) that would have seemed unthinkable. ”

Are the lessons finally being learned?

The benefits of expanded mandates are innumerable, but most significantly, it allows governments to reaffirm their messages by establishing a strict but simple rule: if you are in public, you must wear a mask.

"A general rule is much easier to adhere to and apply," said Stutt.

But many experts are upset that it has taken so long to arrive, and are imploring other countries to follow suit and make their mask laws black and white.

Mills said she was "really shocked and shocked" by the conflicting guidance from the World Health Organization and many governments, which said at the beginning of the pandemic that the use of masks was not necessary to slow the spread.

WHO Director-General Tedros Adhanom Ghebreyesus said last month that the organization shifted gears and encouraged the use of masks after several weeks because the evidence had evolved. "Our updated guide contains new information on the composition of cloth masks, based on academic research requested by the WHO," Tedros said last month.

"It was really very frustrating as a scientist, (because) there have been many material studies showing that these good, high-quality masks can really stop the leak," said Mills.

In contrast, several Asian countries, many of which experienced the worst SARS epidemic, quickly encouraged citizens to wear masks.

"Think of Japan: They were really effective and clear, they had the Three Cs," Mills said, referring to a government slogan that ordered masks in confined spaces, crowded places, and close contact environments.

"They just keep repeating it and repeating it, and have had around 1,000 deaths in a population of 126 million," he added, noting that Japan's relative success depended on several other factors.

"It is not as simple as this, but those places that wore masks from the beginning had much lower death rates," Stutt added.

The faltering adoption in much of the West was in sharp contrast to Asian countries. But now that governments feel secure enough to set stricter rules, experts can expect mask use to soon return to normal in all public places.

"A strong message from governments and organizations like the WHO has a significant effect on people and makes it much more socially acceptable to wear a mask and increase adoption rates," said Stutt.

"That mandatory use of masks is not going to result in a major rebellion by the majority of the population," added Duffy, citing his research that showed rapid acceptance in the UK.

"There will be fractions that are strongly opposed, that will become a little bigger and more vociferous, and our attention will be directed to those people," he said. "But the reality will be that the majority of the population will adapt and accept it."

- CNN Health's Naomi Thomas contributed to this report.

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