Necessary or not? The debate on the compulsory nature of outdoor chin straps is growing

MADRID.- Wear the chin strap outside and put it in your pocket when you enter a restaurant to eat it’s like wearing a helmet for walking and taking it off while riding a motorbike. However, this paradox is common in countries like Spain, with regulations that impose the chinstrap on the outside, but they make exceptions in the interiors of restaurants and offices.

More and more frontline experts are questioning these contradictory measures, such as epidemiologist Marc Lipsitch, director of the Center for Dynamics of Infectious Diseases at Harvard University (USA). “In general, I’m very radical in defending the rules with a clear advantage, but Putting the chinstrap on the outside has significant costs and there is really no evidence of its benefitsLipsitch warns.

The data has been conclusive for a year now. A study of 318 outbreaks of Covid in China at the start of the pandemic showed that 317 occurred indoors, compared to a single case outside: that of a 27-year-old man who was reportedly infected. in a village talking outdoors with a newcomer from Wuhan. The European agency dedicated to the fight against infectious diseases, ECDC, recommends only wearing the chin strap indoors in public places and suggests that “it may be considered for use in crowded outdoor environments”. However, in Spain, it is compulsory even for a person who walks alone in a park. The public health association of Madrid demanded on April 6 the cancellation of this “absurd” obligation of chinstrap outside.

The coronavirus is mainly airborne, thanks to 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 Dr Trish Greenhalgh, University of Oxford (UK) – insisted on solutions: avoid interiors shared with people who do not live together, increase ventilation, use tight fitting chin straps inside rooms and reduce capacity.

The Madrid Public Health Association has called for the “absurd” obligation to be removed.

Greenhalgh is frank: “Outside, it is enough wearing the mask during intense 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 outside, because the virus in the air dissipates quickly. But If I breathe in the air you just breathed out, I’m in danger», He emphasizes.

Chemical engineer Martin Bazant, author of an interactive tool for calculating the risk of infection, insists that The transmission of the virus by air indoors is the main culprit of the pandemic. Covid has a particular dynamic, in which some infected become super contagious, while others do not transmit the virus even to people they sleep with in the same bed. Bazant recalls that all known massive infections have occurred indoors, such as the outbreak with 53 cases in a church choir in Mount Vernon (United States) or the 23 infected during a bus trip to Ningbo (China). In these closed and poorly ventilated environments, the chin strap is essential.

Bazant, of the Massachusetts Institute of Technology (MIT), points out that “external infections were extremely rare, even at the start of the pandemic, when no one was wearing a mask.” The engineer explains that, on the outside, the air exhaled through the mouth is generally warmer than that of the surroundings, so it tends to rise quickly and is carried away by the currents.

“You can only expect contagion when people are close to each other, one meter or less, and talk face to face, as happened in China in the only recorded case of outdoor transmission. And even in this case, the risk is much lower than indoors, ”underlines Bazant. In his opinion, “It’s time to stop wearing chin straps outside.”

US health officials call for the use of masks on premises and on public transportation, but clarify that “they may not be needed when alone outside and away from others. people, or with people living together ”. The World Health Organization (WHO) He only recommends wearing chin straps outside if they cannot be stored at least three feet away.

“We need outdoor masks if we are in a crowd and very close to others”, says researcher Lidia Morawska.

Over the past year, the researcher has led the scientific movement that has convinced leading health authorities of the importance of airborne transmission of the coronavirus. Morawska, Co-Director of the Air Quality Research Center of Australia-China, is also energetic: “I have always said that outdoors, when you move around and can maintain a reasonable distance, chin straps are not necessary. For example, when you walk in a park, run or cycle. However, we do need outdoor masks if we are in a crowd and very close to others. “

An international team of scientists examined the role of chinstrap in the fight against Covid in January. The authors then suggested its “widespread use” to reduce transmission of the virus. The first author of this article, Jeremy Howard, a data scientist at the University of San Francisco, now points out that “Normally it is not necessary to wear a mask outside”, as long as there is a breeze or the person is walking or running.

Doctor Helene-Mari Van Der Westhuizen, co-author of the January study, also believes that the chin strap is not necessary on a walk without crowds, but points out the complexity of the debate. “If I go to a crowded outdoor market, if I pass someone in a narrow alley or if I am walking with my grandmother without getting the vaccine, then yes, I would clearly be wearing a mask.” said the researcher, from the University of Oxford. Van Der Westhuizen urges the authorities to include these nuances in their recommendations: “Being outside is much safer than being inside, but you should continue to wear a mask if you cannot keep your distance or if you are going to be in contact with a person from a group at serious Covid risk ”.

More than a hundred Spanish experts wrote a public letter on March 25 in which they urged the authorities to “Rethinking prevention recommendations”, taking into account that “the probability of contagion outside is at least twenty times less than inside“. One of the signatories of the letter, chemist José Luis Jiménez, of the University of Colorado, USA, explains that they avoided mentioning that the chinstrap is not needed outdoors and at a distance , because some public health experts feared it was. interpreted that it is never necessary.

A spokesperson for the Ministry of Health said that for the moment “we must continue to maintain all security measures”. A public health expert believes that it is best not to lift the jugular requirement until a higher level of vaccination is achieved. This was done by the Israeli government, which this week eliminated the requirement to wear a mask outside, but only after immunizing 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.

El País, SL

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