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Viewpoint
June 1, 2020

Airborne Spread of SARS-CoV-2 and a Potential Role for Air Disinfection

Author Affiliations
  • 1Brigham and Women’s Hospital, Division of Global Health Equity, Harvard Medical School, Boston, Massachusetts
  • 2Beth Israel Deaconess Medical Center, Division of Infectious Diseases, Harvard Medical School, Boston, Massachusetts
JAMA. 2020;324(2):141-142. doi:10.1001/jama.2020.7603

An April 2, 2020, expert consultation from the National Academies of Sciences, Engineering, and Medicine to the White House Office of Science and Technology Policy concluded that available studies are consistent with the potential aerosol spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), not only through coughing and sneezing, but by normal breathing.1 This response to a White House request for a rapid review of the literature likely contributed to the recommendation from the US Centers for Disease Control and Prevention (CDC) that healthy persons wear nonmedical face coverings, when in public, to reduce virus spread from undiagnosed infectious cases.

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    6 Comments for this article
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    Application of Upper Room GUV in Large Quarantine Centres During COVID-19 pandemic
    Rahul Narang, MBBS, MD, PhD | Professor Microbiology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, District Wardha, Maharashtra, India
    I read the article by Nardell and Nathavitharana with interest. The authors have suggested use of upper room GUV in selected public settings for prevention of airborne infection especially from asymptomatic COVID-19 subjects. The pandemic is fast evolving in India and other resource-limited countries where use of upper room GUV can be more pertinent. These countries are also facing limited availability of PPE including the extended use of N95 respirators after decontamination. Such measures may lead to lower efficacy of PPE and can be tacked by installing upper room GUV that will not only reduce the SARS-CoV-2 but also Mycobacterium tuberculosis, as many patients may be co-infected with both the agents. This will also have role to play in large quarantine centres. In India, as the number of COVID-19 cases is increasing rapidly due to movement of migrant workers, more facilities with large occupancy will be required to quarantine such cases. The situation may worsen after monsoon season sets in. Cities like Mumbai are converting large covered spaces into quarantine areas. In such spaces also the viral load can be reduced by using exhaust fans and upper room GUV while the circulation of air will be maintained by ceiling fans commonly used in India.
    CONFLICT OF INTEREST: None Reported
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    A Simple Custom Could Prevent Spread of SARS-CoV-2
    Koichi Tsunoda, MD, PhD. | National Hospital Organization Tokyo Medical Center
    There are many transmission mechanisms to spread SARS-CoV-2 that should be taken into account. While air sampling for SARS-CoV-2, in a clinical setting, has demonstrated detectable viral RNA, the extent of transmission resulting from airborne particles relative to large respiratory droplets, directly and on surfaces, is not yet known. These authors have concluded that management of the current crisis and preparation for future respiratory viral pathogens should include consideration of the use of upper-room GUV to help mitigate airborne transmission (1). We want to recommend additional measures.

    When people cough and sneeze, they can propel aerosol particles over a
    distance of 8 meters (2), spray tiny drops of infected saliva fall to the ground and floor within seconds. Viral shedding in stool could be a potential route of transmission (3). We walk on the ground and step on the floor in toilet stalls with shoes and the virus can be spread via the tiny droplets that can infect you. Medical staff wear shoe covers for preventing spread of the virus onto the soles of their shoes all over the floor. The greatest threat really lies on the ground and floors.

    Most secondary infections occurred in the household has reported (4). We are concerned about infections acquired at home. In Japan, there is a simple custom of removing shoes at the entryway of a house or apartment before walking indoors to prevent floor moisture due to the hot and humid climate, a practice which greatly reduces the risk of bringing in virus attached to the soles of the shoes and spread of COVID-19 at home. Virus on the floor can become re-aerosolized and enter the air we breathe, which might increase infection risk. Also, wearing outdoor shoes increases risk to children crawling around on the floor at home. That virus can remain on synthetic materials used in shoes for as long as five days has been mentioned (5).

    To reduce the infection of COVID-19, first wipe the dirt off shoes on the doormat and then dip the shoes into tray or box containing 0.5% sodium hypochlorite and water or bleach to sterilize them at the entryway (6). Then take off or wipe the shoes and enter the house (7). It is an easy solution; removing and/or disinfecting the shoes is a very simple custom during a pandemic that could be one of the precautions to save yourself and your family.

    Koichi Tsunoda MD, PhD. & Mihiro Takazawa
    National Hospital Organization Tokyo Medical Center

    References

    1. Nardell EA, Nathavitharana RR. Airborne Spread of SARS-CoV-2 and a Potential Role for Air Disinfection. JAMA. Published online June 01, 2020.

    2. Bourouiba L. IMAGES IN CLINICAL MEDICINE. A Sneeze. N Engl J Med. 2016 Aug 25;375(8):e15.

    3. S. W. X. Ong, et. al. Air, Surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from a symptomatic patient. JAMA, March 4, 2020

    4. Sun K, Viboud C. Impact of contact tracing on SARS-CoV-2 transmission. Lancet
    Infect Dis. 2020 Apr 27.

    5.van Doremalen N, Bushmaker T, Morris DH, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. N Engl J Med. 2020 Apr 16;382(16):1564-1567.

    6. https://www.cdc.gov/vhf/ebola/pdf/cleaning-handwashing-5percent-liquid-bleach.pdf

    7. https://www.cdc.gov/vhf/ebola/hcp/ppetraining/n95respirator_gown/doffing_19.html
    CONFLICT OF INTEREST: None Reported
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    Bipolar Air Ionization Another Potentially Viable Option
    Kent Moore, MD, DDS | Charlotte Oral Surgery
    The authors may not be aware that bipolar plasma ionization may offer another excellent and practical option for management of ambient environmental air. These units have been installed in large medical centers around the world including (but not limited to) Cleveland Clinic, John's Hopkins, Boston Children's, and Atrium (1,2).

    References

    1. https://www.businessinsider.com/bipolar-ionization-could-be-a-secret-weapon-against-covid-19-2020-4

    2. https://globalplasmasolutions-my.sharepoint.com/:p:/p/chris_mauro/EUQ9KTbzkYBDmKQpcoydXwkBz-SMOU8h6N9Y4QmMAqRHLg?e=7faTrw
    CONFLICT OF INTEREST: None Reported
    Airborne vs Surface Contact Spread
    Andrea Vila, MD, Infectious diseases | Hospital Italiano de Mendoza
    I read the article by Nardell and Nathavitharana with interest. Studies that attribute transmission of SARS-coV-2 to air conditioning have not evaluated highly relevant situations such as the use of public toilets. Such a situation could explain some cases in the setting of restaurants and other common places. It seems reasonable to keep focusing on measures of surface hygiene and social distance, before recommending expensive and unproven methods that have been designed to kill airborne pathogens.
    CONFLICT OF INTEREST: None Reported
    Ozone (O3) and a Potential Role for Air Disinfection in Airborne Spread of SARS-CoV-2.
    John Semple, MD, MSc, FRCSC, FACS | University of Toronto
    In the recent “Viewpoint” Nardell and Nathavitharana describe the growing concern regarding the potential for person-to-person airborne transmission of SARS-CoV-2 (1). Although there is no published evidence of documented airborne transmission they present a credible list of examples where sources of transmission in public settings are consistent with the potential for aerosol spread of severe acute respiratory syndrome coronavirus (2). Depending on the pathogen’s route, transmission of viral diseases in indoor settings can potentially be controlled through various procedures including the use of personal protective equipment (1).
    Logically, they argue that if airborne transmission is a real concern and “fitted
    N95 respirators are justified as a prudent precaution against airborne infection for health care workers with exposure to patients with novel coronavirus 2019 (COVID-19) and nonmedical face coverings are justified to be worn in public to reduce aerosol spread, should not air disinfection be deployed in intensive care units, emergency departments, waiting rooms, and ambulatory clinics?” (1). 

    Their subsequent description of notable air disinfectants, however, focuses on UV fixtures (specifically upper-room germicidal UV (GUV)) and the mechanics of effective in-door ventilation but somehow omits the significant role ozone (O3) has in this area. Ozone is a known natural disinfecting agent for which there is a considerable body of research that specifically highlights ozone efficacy in the control of airborne and surface viruses (2, 3). The reactivity of O3 is through oxidation or peroxidation and generation of free radicals, giving rise to a cascade of reactions like peroxidation of lipids leading to changes in membrane permeability. In viruses, the O3 damages the viral capsid and upsets the reproductive cycle by disrupting the virus-to-cell contact with peroxidation (4,5).

    Currently there are no air treatment strategies available for inactivating airborne COVID-19 due to the lack of approved protocols. Both UV light, ozone and disinfecting agents have been tested for other types of airborne phage and virus inactivation (4,5) but none have led to the establishment of standardized air treatment protocols (3).

    We agree with the authors that there needs to be a focus and recommendations from the World Health Organization and the CDC for transmission prevention guidelines in relation to air borne infections for air disinfection in priority areas in health care where aerosol is generated. Management of the current crisis should include a strategy for the use of all disinfecting agents including both O3 and UV in evidence-based guidelines for airborne transmission treatment going forward.

    References:

    1. Nardell EA, Nathavitharana RR. Airborne Spread of SARS-CoV-2 and a Potential Role for Air Disinfection. JAMA. 2020;324(2):141–142. doi:10.1001/jama.2020.7603
    2. Tseng C, Li C. Inactivation of surface viruses by gaseous ozone. J Environ Health. 2008;70(10):56-62.
    3. Dubuis ME, Dumont-Leblond N, Laliberté C, et al. Ozone efficacy for the control of airborne viruses: Bacteriophage and norovirus models. PLoS One. 2020;15(4):e0231164. Published 2020 Apr 10. doi:10.1371/journal.pone.0231164
    4. Weber TP, Stilianakis NI. Inactivation of influenza A viruses in the environment and modes of transmission: a critical review. J Infect. 2008;57(5):361-373. doi:10.1016/j.jinf.2008.08.013
    5. Semple JL, Moore GWK. High Levels of Ambient Ozone (O3) May Impact COVID-19 in High Altitude Mountain Environments [published online ahead of print, 2020 Jun 30]. R
    CONFLICT OF INTEREST: None Reported
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    Citation
    Brett Snodgrass, M.D. | Private Practice
    The authors provide presumably useful information, but no direct citation to the critical work of Wells and Riley: 

    “As defined by Wells and Riley in 1937, true airborne transmission is by infectious droplet nuclei, that is, the 1 to 5 μm dried residua of larger respiratory droplets that stop settling, buoyed by ordinary room air currents, and able to spread far beyond the trajectory of larger respiratory droplets that tend to settle within a meter or so of the infectious source.”

    The JAMA Editor-in-Chief and other interviewers have referenced the distinction between droplet and airborne transmission in multiple
    podcasts and interviews and made some suggestion that the distinction is not dichotomous but occurs along a spectrum.

    If this work by Wells and Riley creates the definitional standard of “airborne transmission” by small drops of fluid in the air, then citation to their work could be useful for readers and appears useful in educating physicians about the distinction between large drop and small airborne drop transmission. Can the authors or editors please provide the citation?
    CONFLICT OF INTEREST: None Reported
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