by Jesús Armando Haro Profesor investigador del Centro de Estudios en Salud y Sociedad, El Colegio de Sonora. Correo: firstname.lastname@example.org
The current debate on the use of face masks in the Covid-19 pandemic contains several edges, which denote that the issue, far from narrowing down to the biological and epidemiological aspects of prevention, affects economic, social, political and cultural spheres. The range of their prescription has ranged from mandatory use, implemented early by China, Korea, Japan, and other Asian countries, then later in other countries, regions, or cities; to emphatic discouragement, with variable recommendations to use them, from the type, if permanent or selective and how to care, reuse or not. They were handled in an ambiguous and changing way, as happened in the United States, as well as with the World Health Organization, which initially advised against, to end up recommending them. In Mexico, attempts have been made to politicize the matter, blaming the health authorities for not making them compulsory, while the Government of Mexico City, as well as other Mexican cities, and even states, such as Coahuila and Yucatan, have implemented its compulsive use in public roads, along with other measures aimed at preventing the transmission of the virus, such as restricting the movement of people, limiting occupants by vehicle, suspending non-essential productive activities and disseminating information on the advantages of staying home, washing hands frequently, keep a healthy distance, isolate yourself and give warning in case of symptoms.
Understanding what is debated in the case of face masks and respirators, leads us to notice two aspects that, although complementary, are still different: prevention thought in individual terms, me and my family; and, from public health, consider that what is relevant is not to abolish but to delay contagion, “flatten the curve so as not to overload the health services”. From clinical prevention, it is convenient to distinguish the conditions in which each domestic group is found to design routines according to their vulnerable members. The use of facial protectors should be guided by a logic that reasons their use to reduce the risk of contagion, without forgetting that it is only a complementary measure that does not absolutely prevent viral transmission.
Understanding it leads us to analyze the biology of SARS-2, the causative agent of Covid-19 and its reception by the human body. This type of betacoronavirus measures between .05 and 0.2 um (microns) in diameter. It is a “vital” form that can only be expressed if it infects living cells, where it reproduces. It is transmitted through droplets and micro-droplets that are respectively sprayed (particles larger than 10 um) and aerosolized (smaller than 10 um), with oral and respiratory secretions, when speaking, sneezing or coughing, with the average incubation period being 5.1 days, although the vast majority of cases are asymptomatic, without knowing the exact time it is transmitted (Meselson 2020). Viral particles can evaporate or fall to the ground within two meters, but also survive up to seven hours in closed environments, where they spread farther away, although their concentration decreases, as happens on plastic and metal surfaces, where it persists between 3 hours and 9 days if there are favorable environmental conditions, as it appears to be inactive relatively early in the sun, in airy conditions, although its viability has not been sufficiently verified. This is why face masks are not enough. It is also pointed out that there is the possibility of acquiring it through the conjunctivae, although it is much more feasible that the main route is the nasopharyngeal, where there are abundant ACE2 proteins to which the virus binds. Although we do not know key factors in its transmission and immune brand, indirect data about other coronaviruses (SARS) suggest that infection by SARS-CoV-2 generates immunity after recovery, given that it is an RNA virus and not DNA, like HIV. But, it can be lethal for those who need to be hospitalized, mostly elderly and chronically ill, although young people, more or less healthy adults, pregnant women and children.
Regarding facial masks and other protectors, the capacity of a mouthpiece is very different from that of an N95 “respirator”, capable of filtering, as its name suggests, up to 95% of airborne particles, thanks to a polypropylene nanofiber filter, guaranteed not to let micro-droplets pass, although it is not suitable for gases or vapors, despite the hermetically sealing mouth and nose, making it uncomfortable for prolonged use. Although they are more expensive, they are considered reusable. In contrast, surgical masks and other face masks only protect against visible droplets. They are effective at hampering large particles, which may contain viruses, bacteria, or other germs, but not aerosolized ones. And they are disposable. On the other hand, artisan masks, even when they are not very effective – they are made of different materials – constitute a particularly useful barrier for not transmitting to others, being mostly reusable after disinfection.
Since the “Spanish” influenza of 1918, facial protectors began to be used as a preventive measure, but it was not until 1972, when the 3M company developed the first respirator capable of filtering microparticles, with a technology developed to manufacture bras. Since before the 2009 pandemic of influenza A (H1N1), the preventive usefulness of both mouthguards and N95 respirators began to be debated, especially in health workers, being in 2013 when the National Institute for Occupational Safety and Health (NIOSH) of the United States, implemented its mandatory use in hospitals with risk of respiratory infections.
Since then, various studies have been carried out that show favorable findings to recommend the use of both in specific circumstances. As several researchers point out, in any case, it is always better to carry some barrier than not to bring one, if one considers not only the possibility of contagion, but also the intensity or viral load of the exposure (Milton et al 2013). Our immune system has a better chance of getting away with a minimal, even repeated, load than a massive virus invasion. Other works point out the negative effects of prolonged use of both, arguing that the breath moistens them and favors reservoirs for various microorganisms- It is recommended to use them for a limited time or change them, in addition to taking care of other measures, such as not touching it from the front when removing it, not use it as a chin strap and proceed to store and disinfect it, with various methods, depending on the type. Research has been published that highlights the cultural impacts of protectors, their increase according to the incidence of cases and how they affect physical distancing, highlighting that they were rarely used in a unique way, but in conjunction with other preventive measures, such as handwashing, the closure, control and sanitation of surfaces in public spaces and courtesy sneeze, among others. Some conclude that facial protectors are perhaps the most cost-effective preventive measure, estimating a reduction in infections of 10% in the general population and up to 50% in those who wore them (Mniszewski et al 2013).
During the current pandemic the use of face shields has become politicized, especially from speculation subsequent to its high demand, with global scarcity, which has increased, for example, the price of the N95 from 0.65 cents to almost three per unit, in addition to causing international acts similar to piracy. The shortage contrasts with the contamination registered in various beaches of the world with waste, as well as the just claims of health personnel at the national and international levels for the shortage. Also, with the creativity to design various types of protectors, including those with full 3D masks, handcrafted prints or embroidery, even palm; or airtight-seal respirators made from industrial towels, copper mesh, and other polymer “non-woven fabrics.” Several systematic reviews (Stern et al 2020, Xiao et al 2020) indicate that the studies are not conclusive, but, in their methodology, they exclude the majority of works carried out, because they do not meet certain stipulated criteria, such as selection of the samples, the absence of adequate tests and other control strategies, to conclude, paradoxically, that the information is not conclusive, as it is not consistent or comparable. Relevant findings, such as community experiments in Japanese schools, where mask covers proved to be as effective as vaccines (Uchida et al 2017), or controlled clinical trials in health services, which in other reviews demonstrate the effectiveness of face mask and respirators to prevent acute respiratory infections, are discarded. (Offedu et al 2017). Others highlight the synergy of measures (Pan et al 2020), when combined, for example, with handwashing (Smith 2015).
Nor do critics of public use mention why specialists who have years of research on the subject, such as Robert Hecht, Nancy Leung, Raina MacIntyre and Shan Soe-Lin, among others, recommend any type of facial protection in risky situations, such as measure of personal and also collective prevention, because, finally, it is a matter of reducing the rate of incidence and not of abolishing the contagion, for which it would perhaps be necessary to spread the use of N95 at the community level, as well as to apply other measures already proven, including in addition to those described, temperature monitoring, follow-up of cases and contacts, tests on suspects and sentinel sampling, which should be added to a strict household restriction. But it would not be desirable for group immunity, just as it is not desirable to prolong the quarantine too long, due to its economic and social impacts.
Although the climatic effects on the biology of the virus are still unknown, the effectiveness of other practices remains to be verified, such as ventilation of public spaces (Gao et al 2016), humidification of dry environments (Reiman et al 2018) and selective use of ultraviolet light to disinfect objects (McDevitt et al 2012). The reasoned use of protectors is justified both clinically in vulnerable cases and at the collective level, as there are recent works that suggest that almost 80% of infections occur through contact with people who are not diagnosed, as was demonstrated in China (Li et al 2020). Other works (Backer 2020) suggest the influence of sunlight on transmission and a better clinical course of Covid-19 in those infected, although the information on the climatic effects is not yet conclusive (O´Really, KM Auzenbergs, Y. Jafari et al. 2020). In any case, exercise, which combines air and sunlight, is one of the few proven strategies to increase immunity (Shephard, et al 1991).
Christos Lynteris recently wrote in The New York Times, “Understanding epidemics not only as biological events, but also as social processes is key to successful containment. Members of a community wear masks not only to protect themselves from disease. They also use them to demonstrate that they want to be, and bear, together the scourge of contagion”. This signals one of the cultural changes of the present pandemic, where it is ceasing to be a cause of stigmatization to become a courtesy mark. Although it is alluded that wearing a mask can lead to avoiding the rest of the measures, such as disinfecting the items that are brought home or taking off shoes, in practice one observes that wearing it makes it easier to maintain attention on these and other preventive measures, acting as a reminder. However, its reasoned use depends on the person and the context. If a vulnerable person is cared for at a domestic level, the surgical mask or face mask is recommended only in the near moments. It is about going out, wearing it only in places where physical distance is not guaranteed or are closed, without natural ventilation, for which it is best to get a handmade mask, preferably made with synthetic nanofibers. If you have symptoms, do not go out except to go to the doctor, in which case, it is very important to carry protection all the time. Its use in people who are not under house restriction, such as merchants and other workers, should be guided by crowded circumstances, such as public transport. The N95 must be left for health personnel, since they are scarce and there are already more than 140 deaths attributable to the lack of personal protective equipment, among more than 13 thousand deaths recorded in the first week of June in Mexico. If we already have one, remember that it is not recommended to use more than 5 times, although with the relative and complementary principle that is recommended, its use can be extended by drying it in the sun. Currently, the evidence of the important role that asymptomatic carriers of the virus have in the transmission of the disease tends to consolidate, so the protector is emerging as a sensible measure to be incorporated collectively, which requires designing models and modes of use according to the that each situation deserves in particular, with bioecological, socioeconomic and cultural criteria. The issue denotes that common sense needs science, but that it must also benefit from good sense, referring to achieving more with few resources.
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