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“Exercise with facemask; Are we handling a devil’s sword?” – A physiological hypothesis – NCBI

Straying away from a sedentary lifestyle is essential, especially in these troubled times of a global pandemic to reverse the ill effects associated with the health risks as mentioned earlier. In the view of anticipated effects on immune system and prevention against influenza and Covid-19, globally moderate to vigorous exercises are advocated wearing protective equipment such as facemasks. Though WHO supports facemasks only for Covid-19 patients, healthy “social exercisers” too exercise strenuously with customized facemasks or N95 which hypothesized to pose more significant health risks and tax various physiological systems especially pulmonary, circulatory and immune systems. Exercising with facemasks may reduce available Oxygen and increase air trapping preventing substantial carbon dioxide exchange. The hypercapnic hypoxia may potentially increase acidic environment, cardiac overload, anaerobic metabolism and renal overload, which may substantially aggravate the underlying pathology of established chronic diseases. Further contrary to the earlier thought, no evidence exists to claim the facemasks during exercise offer additional protection from the droplet transfer of the virus. Hence, we recommend social distancing is better than facemasks during exercise and optimal utilization rather than exploitation of facemasks during exercise.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7306735/

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Estimated Inactivation of Coronaviruses by Solar Radiation With Special Reference to COVID-19 – The National Center for Biotechnology Information

“90 percent or more of SARS-CoV-2 virus will be inactivated after being exposed [to summer sun] for 11 to 34 minutes.”

Using a model developed for estimating solar inactivation of viruses of biodefense concerns, we calculated the expected inactivation of SARS-CoV-2 virus, cause of COVID-19 pandemic, by artificial UVC and by solar ultraviolet radiation in several cities of the world during different times of the year. The UV sensitivity estimated here for SARS-CoV-2 is compared with those reported for other ssRNA viruses, including influenza A virus. The results indicate that SARS-CoV-2 aerosolized from infected patients and deposited on surfaces could remain infectious outdoors for considerable time during the winter in many temperate-zone cities, with continued risk for re-aerosolization and human infection. Conversely, the presented data indicate that SARS-CoV-2 should be inactivated relatively fast (faster than influenza A) during summer in many populous cities of the world, indicating that sunlight should have a role in the occurrence, spread rate, and duration of coronavirus pandemics.

https://pubmed.ncbi.nlm.nih.gov/32502327/

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Increased Risk of Noninfluenza Respiratory Virus Infections Associated With Receipt of Inactivated Influenza Vaccine – NCBI

We randomized 115 children to trivalent inactivated influenza vaccine (TIV) or placebo. Over the following 9 months, TIV recipients had an increased risk of virologically-confirmed non-influenza infections (relative risk: 4.40; 95% confidence interval: 1.31-14.8). Being protected against influenza, TIV recipients may lack temporary non-specific immunity that protected against other respiratory viruses.

In the prepandemic period of our study, we did not observe a statistically significant reduction in confirmed seasonal influenza virus infections in the TIV recipients (Table 3), although serological evidence (Supplementary Appendix) and point estimates of vaccine efficacy based on confirmed infections were consistent with protection of TIV recipients against the seasonal influenza viruses that circulated from January through March 2009 [16]. We identified a statistically significant increased risk of noninfluenza respiratory virus infection among TIV recipients (Table 3), including significant increases in the risk of rhinovirus and coxsackie/echovirus infection, which were most frequently detected in March 2009, immediately after the peak in seasonal influenza activity in February 2009 (Figure 1).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404712/

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Face Mask Use and Control of Respiratory Virus Transmission in Households – NCBI (2009)

The key findings are that <50% of participants were adherent with mask use and that the intention-to-treat analysis showed no difference between arms. Although our study suggests that community use of face masks is unlikely to be an effective control policy for seasonal respiratory diseases, adherent mask users had a significant reduction in the risk for clinical infection. Another recent study that examined the use of surgical masks and handwashing for the prevention of influenza transmission also found no significant difference between the intervention arms.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2662657/

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Complexity of the Basic Reproduction Number (R0) – NCBI (2019)

Although R0 might appear to be a simple measure that can be used to determine infectious disease transmission dynamics and the threats that new outbreaks pose to the public health, the definition, calculation, and interpretation of R0 are anything but simple. R0 remains a valuable epidemiologic concept, but the expanded use of R0 in both the scientific literature and the popular press appears to have enabled some misunderstandings to propagate. R0 is an estimate of contagiousness that is a function of human behavior and biological characteristics of pathogens. R0 is not a measure of the severity of an infectious disease or the rapidity of a pathogen’s spread through a population. R0 values are nearly always estimated from mathematical models, and the estimated values are dependent on numerous decisions made in the modeling process. The contagiousness of different historic, emerging, and reemerging infectious agents cannot be fairly compared without recalculating R0 with the same modeling assumptions. Some of the R0 values commonly reported in the literature for past epidemics might not be valid for outbreaks of the same infectious disease today.

R0 can be misrepresented, misinterpreted, and misapplied in a variety of ways that distort the metric’s true meaning and value. Because of these various sources of confusion, R0 must be applied and discussed with caution in research and practice. This epidemiologic construct will only remain valuable and relevant when used and interpreted correctly.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6302597/

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Understanding the factors involved in determining the bioburdens of surgical masks – NCBI (2019)

Background

Surgical site infection (SSI) continues to be one of the most common postoperative complications. In our previous study, surgical mask (SM) bioburden was identified to be a potential source of SSI. In the present study, we investigated the factors involved in SM bioburden.

Methods

Bioburdens of the disposable SM (A: medical mask; B: medical surgical mask) and newly laundered cloth SM (C) were tested by immediately making an impression of the external surface of the mask on sterile culture media. SM microstructure was observed using a scanning electron microscope (SEM). Filtering efficiency and airflow resistance were evaluated with TSI Automated Filter Tester 8130 (TSI Incorporated) according to GB/19083-2010. Whether speaking during operation and washing the face pre-operatively affect SM bioburdens was also evaluated. Surgical procedures were performed in a dynamic operation room. Fifty cases of mask use were enrolled in this study.

Results

The bioburden of mask A was the highest. The bioburden of mask B was the lowest. Mask C possessed the lowest filtering efficiency and the highest airflow resistance. SM bioburden was higher in the speaking group. SM bioburden showed no significant difference after washing the face, despite the finding that washing could significantly reduce facial bioburden.

Conclusions

Multiple factors influence SM bioburdens. Mask B showed the lowest bioburden and best protection effects. Mask C is not recommended to be used, especially considering that surgeons do not wash the cloth masks daily. Unnecessary talking during operation is not recommended, and washing the face before surgery is not strictly necessary.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6989980/

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Surgical masks as source of bacterial contamination during operative procedures – NCBI (2018)

Background
Surgical masks (SMs) are used to reduce bacterial shedding from the mouth, nose and face. This study aimed to investigate whether SMs may be a potential source of bacterial shedding leading to an increased risk of surgical site infection.

Methods
Bacterial contamination of the SMs was tested by making an impression of the external surface of the mask on sterile culture media immediately. We investigated the difference in bacterial counts between the SMs worn by surgeons and those placed unused in the operating room (OR), and the bacterial count variation with indicated wearing time. Moreover, the difference in bacterial counts on the external surface between the first and second layers of double-layered SMs was also assessed.

Results
The bacterial count on the surface of SMs increased with extended operating times; significant difference was found between the 4- to 6-hour and 0-hour groups (p < 0.05). When we analysed the bacterial counts from the same surgeon, a significant increase was noted in the 2-hours group. Moreover, the bacterial counts were significantly higher among the surgeons than the OR. Additionally, the bacterial count of the external surface of the second mask was significantly higher than that of the first one.

Conclusions
The source of bacterial contamination in SMs was the body surface of the surgeons rather than the OR environment. Moreover, we recommend that surgeons should change the mask after each operation, especially those beyond 2 hours. Double-layered SMs or those with excellent filtration function may also be a better alternative. The translational potential of this article This study provides strong evidence for the identification that SMs as source of bacterial contamination during operative procedures, which should be a cause for alarm and attention in the prevention of surgical site infection in clinical practice.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6037910/

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Amending Koch’s postulates for viral disease: When “growth in pure culture” leads to a loss of virulence – NCBI (2016)

It is a common laboratory practice to propagate viruses in cell culture. While convenient, these methodologies often result in unintentional genetic alterations, which have led to adaptation and even attenuation in animal models of disease. An example is the attenuation of hantaviruses (family: Bunyaviridae, genus: Hantavirus) when cultured in vitro. In this case, viruses propagated in the natural reservoir species cause disease in nonhuman primates that closely mimics the human disease, but passaging in cell culture attenuates these viruses to the extent that do not cause any measurable disease in nonhuman primates. As efforts to develop animal models progress, it will be important to take into account the influences that culture in vitro may have on the virulence of viruses. In this review we discuss this phenomenon in the context of past and recent examples in the published literature.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5182102/