PerspectiveViewpoint: COVID-19

Reducing transmission of SARS-CoV-2

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Science  26 Jun 2020:
Vol. 368, Issue 6498, pp. 1422-1424
DOI: 10.1126/science.abc6197

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  • RE: Dr. D.V. Gokhale

    This is very interesting and realistic perspective on reducing the transmission of SARS-CoV-2 infection suggesting emphatically the use mask to combat the asymptomatic spread via aerosoles and droplets that are less than 1micron. The authors pointed out the limitations of social distancing of 6 feet recommended by CDC. These recommendations were based on studies on the infected droplets of 100 microns thrown out by coughs and sneezes of the infected individual. These droplets being heavy, settle down due to gravitation force. Probably, nobody thought of droplets or particles of less than 1 micron size produced in sneezes and coughs which remain in air for hours together and carried away to longer distances because winds and breezes. These droplets may be more responsible for spreading of COVID-19 disease. However, not much information is available on the role of airborne infectious droplets in causing COVID-19 and hence the conclusions of this perspective seems to be illogical. It is necessary to undertake such studies to authenticate the airborne transmission of SARS-CoV-2 virus which will help CDC to take decisions and and issue recommendations to reduce the speard of COVID-19 disease.

    Competing Interests: None declared.
  • RE: Wearing a mask in the era of COVID-19 makes all the difference
    • Shibo Jiang, Professor, School of Basic Medical Sciences, Fudan University, Shanghai, China
    • Other Contributors:
      • Chungen Pan, Senior Investigator, Haid Research Institute, Guangdong Haid Group Co., Ltd., Guangzhou, China

    Prather, K. A. et al. have raised a good point - places that have been most effective in reducing the spread of COVID-19 have implemented universal masking (1). While most countries of Eastern Asia have been successful in controlling the COVID-19 pandemic, many European/American countries continue to suffer from rapid spread of the virus. Virus transmission in three East Asian countries, including Japan, South Korea, and China, seem to be under control, as their total infection curves have been almost horizontal from February 20 to May 15, 2020, whereas the curves of many European/American countries have risen very fast, especially that of the USA, which is almost vertical. What accounts for this difference?

    Close interactions among people in large clusters, such as workplaces, may contribute to the number of infections. It follows that countries with greater populations would spread the coronavirus faster. Yet, compared with one country (USA) from North America and five countries from Europe, the three East Asian countries have higher population density. This seems to indicate that high population density did not accelerate virus transmission in these countries. Establishment of travel restrictions worked successfully in controlling the pandemic early in the year in China, but it was not helpful in the Western countries, possibly because it is too late to take these measures. Iinterestingly, no strict travel restrictions have been implemented in Japan and South Kor...

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    Competing Interests: None declared.
  • Reducing transmission of SARS-CoV-2 - the clinical relevance and practical application of scientific research studies during a global Pandemic
    • Dr Dianne Sika-Paotonu CQS MRSNZ, Associate Dean (Pacific)/Senior Lecturer Pathology & Molecular Medicine, Wellington School of Medicine & Health Sciences, University of Otago, New Zealand

    To the Editor,

    I read with keen interest the perspective piece by Prather, K. A. et al. (1) and titled “Reducing transmission of SARS-CoV-2”.

    This perspective piece provides a brief and helpful summary of some of the studies related to airborne transmission of respiratory disease, in the context of the current Pandemic crisis and the issue of asymptomatic transmission.

    Masks and widespread testing are integral to combating asymptomatic spread in aerosols and droplets, and in particular the identification and isolation of symptomatic and any asymptomatic individuals as rapidly as possible, is also essential.

    The role of rapid and effective contact tracing processes, lockdown and quarantine measures coupled with the appropriate border controls are also absolutely critical in managing this current global crisis.

    It is also a necessity to ensure availability and communication of the scientific studies underpinning the public health and physical distancing recommendations being put forward during the current COVID-19 pandemic.

    This helps provide assurance that a sound evidence base underlies the decisions and recommendations being made.

    This also provides a valuable opportunity for children and young people – the next generation of scientists, to see the immediate clinical relevance and the important practical application of scientific research studies during a global Pandemic.

    Overall this brief review provides a he...

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    Competing Interests: None declared.
  • RE: Nebulizer therapy with isotonic saline to decrease aerosol transmission of SARS-CoV-2

    The ongoing response to COVID-19 pandemic remains focused on social distancing measures to slow the spread of SARS-CoV-2. Airborne transmission of virus-containing aerosols produced by asymptomatic individuals appears to be the main mechanism responsible for the spread of COVID-19. In their Perspective article ‘Reducing transmission of SARS-CoV-2’ (27 May 2020: eabc6197), K. A. Prather et al. discuss the need for control measures that will reduce aerosol transmission of SARS-CoV-2, specifically, universal masking and widespread testing to identify and isolate infected asymptomatic individuals (1).
    In this context, it is somewhat surprising that the study by Edwards et al. (2004) has not received much attention. Edwards et al. found that superemitters (human subjects that expire excessive bioaerosol particles during quiet breathing) could potentially play the role of superspreaders for respiratory pathogens. More importantly, they have shown that the administration of nebulized isotonic saline in such individuals significantly diminished the number of exhaled bioaerosol particles for up to 6 hours (2).
    Nebulization therapy in general has a good safety profile, is suitable for most patients (including children, elderly, patients on mechanical ventilation), and is widely used in many respiratory diseases (3). The effectivity of such an intervention in the context of SARS-CoV-2 transmission can be rapidly determined in the current outbreak scenario. Once assessed,...

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    Competing Interests: None declared.
  • RE: An idea

    What if you get a covid positive person to wear a mask in a sterile space the has vertical petri dishes set up at various distances. Have the person cough. Next room/space, same, but no cough. Next room/space, different type of mask, etc.

    Competing Interests: None declared.
  • RE: Confusion over social distancing rules
    • Shashank S. Tiwari, Research Fellow, Canadian Institute for Genomics and Society, Toronto, ON, Canada

    Though the perspective has highlighted the importance of social distancing, it has a factual error.  Prather et al wrote that "the World Health Organization (WHO) recommendations for social distancing of 6 ft and hand washing to reduce the spread of SARS-CoV-2 are based on studies of respiratory droplets carried out in the 1930s".  However, the WHO recommends just 3 ft of social distancing.   I think, the reason for the confusion is the US CDC, which recommends 6 ft of social distancing. The Covid-19 became a classic case of extreme scientific confusion especially in terms of social distancing.  There is a discrepancy in social distancing rules across different countries. Some countries follow the WHO recommendations, other countries follow the US CDC , and a few others opted for the average of the two recommendations. For instance, India recommends 1 meter (3ft) . In contrast, Australia suggests keeping 1.5 meters away from others wherever possible.  Japan adopted 1.8 (6ft) meters rule.  These variations create confusion among people in a given globalized world and raise a legitimate question on 'discrepancies in expert advice' for the same science. 

    Competing Interests: None declared.
  • Illogical conclusion

    The authors suggest that COVID-19 aerosol spread approximates the diffusion of cigarette smoke, and that such aerosols produced by asymptomatic infected individuals can efficiently infect others. If so, then it does not follow logically that cloth masks, even with social distancing, could possibly support safe return to crowded urban social life. The authors should rethink their premise, as they show no evidence of scientific tentativeness and zeal to falsify their hypothesis that are the hallmarks of evidence-based medicine and public health. It is tempting to abandon high standards of evidence during a pandemic. However, a well designed, safety monitored, adaptive randomized controlled trial is necessary and ethical to test the unproven hypothesis that mandatory masking is effective and safe (as worn by the general public, properly or not). Masks may potentially be contaminated, concentrating virus on the face. Are they assumed to be absolutely safe?

    Competing Interests: None declared.
  • RE: Can we reduce transmission of SARS-CoV-2 by Nasal Wash?

    Perspective by Prather et al brought the aerosol transmission of COVID-19 by the asymptomatic individuals in the frontline and posed further challenge. Particles of aerosol can be scattered over a wider area and can cause more severe diseases as they might evade the ‘natural ambush’ of long slender respiratory tract to instantly reach the lung alveoli.
    Mask, distancing and hand wash might not be able to control the aerosol adequately. Virucidal effect of drugs might not be effective due to their higher load at symptomatic stage [Ref 6] unlike SARS and MERS. Vaccine is not expected to be the magic bullet. So what can be done in this pandemonium?
    If we ponder from a different point of view, we might get a solution.
    At the outset, COVID-19 virions replicate in nasal epithelial cells with hurdles as the nasal mucus gel is the barrier and keeps the virions away from nasal epithelial cells. Nevertheless, eventually, they increase the virion load which is the factor for transmissibility, pathogenicity, fatality [1] and drug resistance [Ref. 6]. So, we have to reduce the virion load.
    We, pediatric surgeons, do prophylactic bowel wash with saline water to clear the load of microorganisms from gut, prior to some surgeries to protect small infants from wound infection, sepsis, septic shock or death.
    COVID-19 virions are ‘surface virions’ as they replicate and shed on nasopharyngeal epithelial surface and they ar...

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    Competing Interests: None declared.
  • RE: Ignore masks when we exit from lockdown reopen is illogical

    Most people practise the trio of social distancing, hand washing and cough etiquette religiously but many still do not believe that wearing mask is helpful. Comparing these interventions,

    ● All aim at preventing infections arising from droplets.
    ● Mask is a form of source control. Social distancing and hand washing are mitigative. In public health, source control takes precedence.
    ● Though clinical trial evidence on all of them is either poor or non-existent, all four are based on sound scientific and mechanistic principles
    ● Masks act on a continuous basis. No one can wash their hands every 10 minutes. And to reopen social distancing has to relax.

    National authorities in 90 countries and august bodies such as the Royal Society in the UK have recommended mass masking in the community when we exit from lockdown. Sceptics on masks think that they are all wrong. It is possible - there are many examples in the history of science and public health where experts and authorities made erroneous judgements. If they are indeed wrong on masks, we would have wasted our time wearing them but there are little serious harms. However, if they are correct and we ignore the advice, the consequences are far more serious. Asymptomatic transmissions is an important driving force behind this pandemic. Also, <10% of cases may be responsible for 80% of secondary cases. Masking is an important tool that would help to limit the number of cases arising from these...

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    Competing Interests: None declared.

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