In addition to the physical barrier effect, the aids ensure the maintenance of a high temperature in the nasal cavities which favors the secretion of specific defense antibodies (SIgA)
Masks s, masks no. Indoors or even outdoors. The debate on physical protections against the advance of Sar-Cov-2 in the umpteenth variant, the Omicron, has returned to occupy the political arena and also the public one of social networks. Three days ago, the Minister of Health, Roberto Speranza, stated that masks are still a fundamental tool in the strategy to combat Covid and we must keep our guard up in the fight against the virus. Faced with the new infectious peaks, the government is considering making them mandatory again
even outdoors. The same Franco Locatelli, president of the Higher Health Council and coordinator of the Scientific Technical Committee, told Sky TG24 that the hypothesis of an outdoor mask obligation for all of Italy, at least during holidays, may be a possibly considerable measure, if there were any conditions that worsen further.
Defense actions
But what are they the defense actions taken once the mask is worn (and not just any one) and what are the physiological mechanisms that are triggered? In addition to filtering, the most effective defensive weapon ensured by the masks maintaining a high temperature in the nasal passages which represent the first line attacked by coronaviruses. He confirms it a revision studies on the subject (here you find the study
) conducted by ten universities and research centers (eight Italians, one Iranian and one Swiss), published in theInternational Journal of Environmental Research and Public Health.
The use of the mask outdoors has a dual function: of bidirectional physical barrier against droplets of saliva containing virions, for the wearer and those in the immediate vicinity; and of maintain the physiological temperature and humidity inside the airways, supporting the innate immune system, which in the initial stage of a viral infection it can inhibit or disable every first settlement of pathogens within the nasal cavity, he explains Luciano Bubbico, otolaryngologist of the Neurosensory Disabilities Research Unit of INAP (National Institute for Public Policy Analysis) and co-author of the study together with another Italian, Luca Cegolon, of the University of Trieste.
Colonized airways
As with other respiratory viruses, the epidemic waves caused by Sars-Cov-2 erupt during the winter months (December-February). According to what has been studied so far, Sars-Cov-2 has a tendency to colonize the upper airways, particularly the nasal cavity, where the temperature is lower than inside the human body. In the presence of a harsh climate the human body to maintain a physiological temperature reduces blood flow to the extremities diverting it to vital organs. The nasal cavity which is highly vascularized is one of the first areas to cool down.
After prolonged exposure to the cold we have all experienced the sensation of an icy and dry nose precisely because the blood is recalled to the internal organs so as not to go into hypothermia. In this situation the activity of the nasal immune system of mucociliary defense, the body’s first line of defense, is drastically reduced favoring the penetration of the virus, which at low temperatures is able to bind more firmly to the host’s receptors through the spike glycoprotein, adds Bubbico.
Secretory immunoglobulins come into action
Airway mucus is the first barrier double layer (gel and periciliary / sol) that the pathogens encounter and composed mainly of water (95%) and various other molecules produced by goblet cells and submucosal nasal glands. With approximately 200-300 cilia in each single respiratory epithelial cell, the process of constant elimination based on microtubules another fundamental defense first line against microbes. But then immunoglobulins enter the scene, the molecules involved in the human body’s immune response against the enemies that attack it. widely accepted that Secretory immunoglobulin (SIgA) represents the “first line of defense” against various pathogens due to its ability to directly inhibit the proliferation of pathogens in the mucosa. According to the literature, reduced levels of SIgA of the mucosa of the airways lead to an increased risk of developing upper respiratory tract infections, Bubbico says.
And here we come to the point. Cold exposure inhibits IgA secretion in the upper respiratory epithelium, which explains the increased frequency of respiratory infections in the cold season. it was also reported that the vasoconstrictor response reflected in the epithelium of the nasal cavity and upper respiratory tract, triggered by surface cooling, leads to a decreased blood flow and white blood cell supply by reducing IgA secretion and allowing the virus to replicate more effectively at low temperatures. Secretory IgA (sIgA) is currently recognized as one of the main effectors of mucosal immunity, he points out.
Much more than a simple scarf effect
In short, common experience: in the cold, even the simple use of the scarf allows the rapid heating and humidification of the nose. Not to mention the sense of internal well-being due to the marked reduction in heat loss. Wearing the mask outside during the winter therefore allows the upper airways to warm up, generating an unfavorable microclimate for the establishment and spread of Sars-Cov-2, representing an additional defensive barrier.
December 17, 2021 (change December 18, 2021 | 09:29)
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