Top scientists question the mandatory mask outdoors and with distance

En español

• Top-level scientists question obligatory use of face masks in open air and with social distancing

Wearing the mask outdoors and putting it in your pocket when entering a bar is like wearing a helmet when walking and taking it off when riding a motorcycle. However, this paradox is common in countries like Spain, with regulations that impose the mask outdoors, but make exceptions in the interiors of restaurants and offices. More and more front-line experts are questioning these contradictory measures, such as epidemiologist Marc Lipsitch, director of the Center for Dynamics of Infectious Diseases at Harvard University (USA). "Generally I am very radical in defending the rules with a clear benefit, but wearing the mask outdoors has significant costs and there is really no evidence of its benefits," Lipsitch warned Monday.

The data has been conclusive for a year now. A study of 318 outbreaks of covid in China at the beginning of the pandemic showed that 317 occurred indoors, compared to a single case outdoors: that of a 27-year-old man who, allegedly, was infected in a town speaking outdoors with a newcomer from Wuhan. The European agency dedicated to the control of infectious diseases, the ECDC, only recommends using a mask inside public places and suggests that “it can be considered for use in open-air environments with many people”. However, in Spain it is mandatory even for a person walking alone in a park. The Madrid Public Health Association requested on April 6 the cancellation of this "absurd" obligation of outdoor masks.

The coronavirus is transmitted predominantly through the air, through aerosols that accumulate like invisible smoke when talking or coughing, according to a scientific team a week ago in the medical journal

The Lancet

.

The authors - led by the doctor Trish Greenhalgh, of the University of Oxford (United Kingdom) - emphasized the solutions: avoid the interiors shared with people who do not live together, increase ventilation, use well-fitting masks inside the premises and reduce the capacity .

The Madrid Public Health Association has requested the annulment of the "absurd" obligation

Greenhalgh is blunt: "Outdoors it is only necessary to put on the mask when we do strenuous exercise, for example when running, if we pass very close to other people, for example on a sidewalk." The researcher suggests keeping a respectful distance. “For the rest, it is not necessary to wear a mask outdoors, because the virus in the air dissipates quickly. But if I inhale the air that you just exhaled, I am at risk ”, he emphasizes.

Chemical engineer Martin Bazant, author of an interactive tool to calculate the risk of infection, insists that airborne transmission of the virus indoors is the main culprit in the pandemic. Covid has a peculiar dynamic, in which some infected become super contagious, while others do not transmit the virus even to the people with whom they sleep in the same bed. Bazant recalls that all known mass infections have occurred indoors, such as the outbreak with 53 cases in a church choir in Mount Vernon (USA) or the 23 infected on a bus trip in Ningbo (China). In those closed and poorly ventilated environments the mask is essential.

Bazant, from the Massachusetts Institute of Technology, stresses that "outdoor infections have been extremely rare, even at the beginning of the pandemic, when no one was wearing masks." The engineer explains that, outdoors, the air exhaled through the mouth is usually warmer than that of the environment, so it tends to rise quickly and is carried away by currents. “Contagion could only be expected when people are close to each other, one meter or less, and talking face to face, as happened in China in the only recorded case of outdoor transmission. And even then the risk is much lower than indoors, ”Bazant emphasizes. In his opinion, "it is time to stop using outdoor masks."

The US health authorities do request the use of masks in the premises and public transport, but clarify that "they may not be necessary when being outdoors alone and away from other people, or with people who are living together."

The World Health Organization only recommends using masks outdoors if they cannot be stored at least one meter away.

"We need outdoor masks if we are in a crowd and very close to other people," says researcher Lidia Morawska

Over the last year, the researcher Lidia Morawska has led the scientific movement that has convinced the main health authorities of the importance of the airborne transmission of the coronavirus. Morawska, co-director of the Australia-China Air Quality Research Center, is also blunt: “I have always said that outdoors, when you are moving and can keep a reasonable distance, masks are not necessary. For example, when walking in a park, running or riding a bike. However, we need outdoor masks if we are in a crowd and very close to other people. "

An international team of scientists reviewed the role of masks in the fight against covid in January. The authors then suggested the "widespread use" of masks to reduce transmission of the virus. The first signer of that work, Jeremy Howard, a data scientist at the University of San Francisco, now emphasizes that "normally it is not necessary to wear a mask outdoors", as long as there is a breeze or the person is walking or running.

Physician Helene-Mari Van Der Westhuizen, a co-author of the January study, also thinks the mask is unnecessary on a walk without crowds, but adds to the complexity of the debate. "If I go to a crowded outdoor market, if I run past someone in a narrow alley, or if I take a walk with my grandmother without vaccinating, then yes, I would clearly wear a mask," says the researcher, from the Oxford University. Van Der Westhuizen invites the authorities to introduce these nuances in their recommendations: “Being outdoors is much safer than being indoors, but you have to keep wearing a mask if you cannot keep your distance or if you are going to be in contact with a person from a group at risk of severe covid ”.

More than a hundred Spanish experts wrote a public letter on March 25 urging the authorities to "rethink prevention recommendations", taking into account that "the probability of contagion outdoors is at least twenty times less than indoors" . One of the signatories of the letter, the chemist José Luis Jiménez, from the University of Colorado (USA), explains that they avoided mentioning that the mask is unnecessary outdoors and from a distance, because some public health experts were afraid that be interpreted that it is never necessary.

A spokeswoman for the Ministry of Health affirms that for the moment "we must continue to maintain all security measures."

A public health expert believes that it is better not to open the melon of the mask until you reach a higher level of vaccination.

This has been done by the Government of Israel, which this week has eliminated the obligation to wear a mask outdoors, but only after vaccinating more than half of the population.

In Spain, 21% of citizens have already received at least one dose, but only 7.6% are fully vaccinated against covid.

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