Currently, humanity is waiting to see the outcome of the current round of vaccines, as well as more effective treatments, capable of offering maximum control against SARS-CoV-2, whose protein capacity causes clinical manifestations that range from the total absence of symptoms even pneumonia, acute respiratory distress, and death. In this long wait, the scientific community continues to analyze all the factors that can, at least, minimize the devastating effects that the new virus has caused in a high percentage of the world’s population.
Mask Can Reduce the Severity of Infections
Along these lines, appears the comment published in The New England Journal of Medicine by immunologists Monica Gandhi and George W. Rutherford, from the University of California, San Francisco (United States), which although it is a hypothesis, offers very interesting virological, epidemiological and ecological data: universal facial masking can reduce the severity of infection in affected people and increase, on the other hand, the chances that new cases will be asymptomatic.
Universal use of the Mask
Does the universal use of the mask thus become a unique and current way to achieve a certain immunization while waiting for a vaccine? From the outset, a mild or asymptomatic disease could be considered a triumph in a pandemic context in terms of prevention and, if confirmed, one of the few pillars of control of the pandemic, which continues to spread worldwide. If this hypothesis is confirmed, the universal use of the mask could become a form of “variolation” that would generate immunity and, therefore, “slow down the spread of the virus while we wait for a vaccine”, the authors point out. Variolation or variolization is a prophylaxis procedure that began to be practiced, even in ancient civilizations, to generate an immune response in pathologies such as smallpox, inoculating the virus, and that was applied before the development of a vaccine by the British Edward Jenner. The technique consisted of making an incision in the individual’s skin and putting the powder from the smallpox scabs. Afterwards, the incision was closed and the inoculated was isolated until the disease attacked him in a mild way, until he recovered.
SARS-CoV-2 Viral Shedding from the nose and mouth
In March, the potential role of facial masking began to become apparent throughout the population when reports began circulating describing the high rates of SARS-CoV-2 viral shedding from the nose and mouth of patients who were pre-symptomatic or asymptomatic. : dissemination rates were equivalent to those of symptomatic. Thus, a month later, the United States Centers for Disease Control and Prevention (CDC) recommended that the population wear cloth face coverings in areas with high rates of community transmission, a recommendation that has been unevenly followed in the United States, according to the authors of the article.
Boston University Study Insight
When this evidence is related to other respiratory viruses, it is also suggested that facial masking can protect the user from infection, by blocking the entry of viral particles into the nose and mouth, a phenomenon that was evidenced during the SARS pandemic of 2003 and that contributed to its control. More recent data from Boston University shows that SARS-CoV-2 infections decreased among healthcare workers after universal masking was implemented in municipal hospitals at the end of last March.Other data report that in an outbreak on a closed Argentine cruise ship, for example, where passengers received surgical masks and staff received N95 masks, the asymptomatic infection rate was 81% (compared to 20% in previous outbreaks of cruise ships without universal masking).
Reducing the Viral Load is KEY
The possibility of an “immunity” through the universal use of a mask is related to a theory of viral pathogenesis, which maintains that the severity of the disease is proportional to the viral inoculum received. “This form of variolization is a way to decrease the infective inoculum. Until a vaccine is available, it is important to reduce exposure time; in this case, with the use of a universal mask that is presented in this article as a strategy to reduce the severity of the infection in those affected and, in addition, to favor asymptomatic infections, ”says Silvia Sánchez Ramón, head of the Hospital’s Immunology Service Madrid clinic, who finds this tactic very suitable for the general population and of special importance for healthcare personnel, especially in exposure situations.
For the immunologist, the key is, therefore, to reduce the infective inoculum, since “its initial load plays a preponderant role in the severity of the infection. Therefore, the key to wearing a mask is to reduce the infective inoculum ”. Since 1938, science has explored, mainly in animal models, the concept of the lethal dose of a virus, or the dose at which 50% of exposed hosts die (LD50). In viral infections in which host immune responses play a predominant role in viral pathogenesis, such as SARS-CoV-2, high doses of viral inoculum can deregulate innate immune defenses, increasing the severity of the disease. In fact, down regulated immunopathology is one mechanism by which dexamethasone improves outcomes in severe Covid-19 infection.
Determining the Severity of SARS-CoV-2
If viral inoculum is important in determining the severity of SARS-CoV-2 infection, an additional hypothetical reason for the use of face masks would be to reduce the viral inoculum to which the user is exposed and the subsequent clinical impact of the disease. “Since masks can filter some droplets that contain viruses (with the filtering capacity determined by the type of mask), the mask could reduce the inoculum that an exposed person inhales. If this theory is confirmed, masking the entire population, with any type of mask that increases acceptability and adherence, could contribute to increasing the proportion of SARS-CoV-2 infections that are asymptomatic ”, the authors point out.
The US CDC estimated that the typical rate of asymptomatic infection with SARS-CoV-2 was 40% in mid-July, although in settings with universal facial masking they were above 80%, providing observational evidence for this hypothesis. But, at this point, wouldn’t an increase in the number of asymptomatic cases be an added risk for community transmission by not detecting infections? Sánchez Ramón considers that the NEJM hypothesis is proposed as a strategy to reduce the severity and achieve asymptomatic infection. And in this last point, as long as a mask is worn indoors and in the event of exposure, it is a possible way to immunize the population through the mask; hence the concept of variolization, without losing sight of the fact that both people with mild symptoms and asymptomatic ones generate immunity ”.
Countries that have adapted entire population masking have fared better, according to the work, in terms of rates of serious Covid-related illness and death, which, in settings with limited evidence, suggests a shift from symptomatic infections to asymptomatic. “The most obvious way to prevent society from suffering the devastating effects of Covid-19 is to promote measures to reduce both the transmission and the severity of the disease. While we await the results of vaccine trials, any Public Health measure that can increase the proportion of asymptomatic SARS-CoV-2 infections can make the infection less deadly and increase the immunity of the entire population without serious illness or death. “Indicate the American immunologists.