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What have we learned about the virus, so far?
by Adrian Gee-Turner, Sterling Presentation Health
“As the pandemic has progressed, our understanding of the virus that causes Covid-19 has grown, and this has influenced the guidance on transmission-prevention measures such as face masks, social distancing, hand washing and disinfection.
"While a few grey areas persist, such as the degree of challenge presented by aerosolised virus, a number of conclusions are emerging.
* Fomite transmission (from objects and surfaces) is highly likely, given the extended periods (days) that SARS-CoV-2 is able to remain viable on a variety of surfaces, including glass and plastic. This is important because people generally touch mobile phones and keyboards many times per day, so as well as hand washing, 'touch points' will need frequent disinfection with an antiviral disinfectant (caution: some 'antibacs' are not antiviral).
* It appears that the viability of SARS-CoV-2 is significantly reduced by sunlight or high temperatures. This conclusion would appear to be borne out by the outbreaks that have occurred in chilled food packing facilities.
* SARS-CoV-2 can remain infectious as an aerosol for at least several hours. This is important because pathogens predominate in small particles of less than 5-microns which do not settle in the way that larger particles do.
Virus survival on surfaces:
The emergence of a novel human coronavirus, SARS-CoV-2, prompted a review of the available data on the persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. Published in January 2020 in the Journal of Hospital Infection, the review examined 22 studies that evaluated the persistence of human coronaviruses such as Severe Acute Respiratory Syndrome (SARS or SARS-CoV-1) coronavirus and Middle East Respiratory Syndrome (MERS) coronavirus.
The assessment detailed the persistence of coronaviruses on inanimate surfaces such as metal, glass and plastic for up to nine days, but found that they can be efficiently inactivated by surface disinfection procedures. It proposed, therefore, that such procedures should be adopted to curtail the further spread of SARS-CoV-2. Interestingly, whilst the Paper concluded that human coronaviruses can remain infectious on inanimate surfaces at room temperature for up to nine days; it also mentioned that temperatures of 30 degrees C or higher reduce the duration of persistence.
Is SARS-CoV-2 different?
In general, the health effects of infection by SARS-CoV-1 are more serious than by SARS-CoV-2, but as a contagion, SARS-CoV-2 is more important because it appears to transmit more easily than its predecessor. This is likely to be because the viral load is highest in the nose and throat of people with Covid-19 shortly after symptoms develop, whereas with SARS, viral loads peak much later in the illness. Consequently, people with Covid-19 may be transmitting the virus even before their symptoms develop. According to the Centers for Disease Control and Prevention (CDC), some research suggests that Covid-19 can be spread by people with no symptoms.
In March 2020, at about the same time that the UK lockdown was first announced, van Doremalen and others published a Paper in the New England Journal of Medicine, which compared the aerosol and surface stability of SARS-CoV-2 in comparison with SARS-CoV-1. The work assessed the viability of the viruses in five conditions: in aerosols, and on plastic, stainless steel, copper, and cardboard. All of the trials were conducted at 40% relative humidity and 21 - 23 degrees C, and found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested.
The research showed that SARS-CoV-2 was more stable on plastic and stainless steel than on copper and cardboard, and viable virus was detected up to 72 hours after application to these surfaces, although the virus titre (viral load) was greatly reduced. The results indicated that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to several days.
Clearly, more work is necessary to better understand the airborne behaviour of the virus. However, a study of the particle sizes of infectious aerosols (July, 2020) published in the Lancet, found that humans produce infectious aerosols in a wide range of particle sizes, but pathogens predominate in small particles (less than 5-microns) that are immediately respirable by exposed individuals. Also, evidence is accumulating that SARS-CoV-2 is transmitted by both small and large particle aerosols. It would appear therefore that masks should be capable of intercepting even ultrafine particles and given the persistence of viable virus in aerosols, facemasks represent an important means with which to limit transmission of the virus.
The effects of temperature and light:
In October 2020, the Virology Journal published work by Riddell and others in Australia, in which the effect of temperature on the persistence of SARS-CoV-2 was evaluated on surfaces including glass, stainless steel and both paper and polymer banknotes. These surfaces were chosen because they represent most of the major 'touch points' such as mobile phones, money, bank ATMs, supermarket self-serve checkouts etc.
All experiments were conducted in the dark, to negate any effects from UV light; SARS-CoV-2 has been shown to be inactivated by simulated sunlight (Ratnesar-Shumate S, et al. (2020), and Schuit M, et al. (2020)). Inoculated surfaces were incubated at 20 degrees C, 30 degrees C and 40 degrees C and sampled at various time points.
The initial viral loads were approximately equivalent to the highest titres excreted by infectious patients, and viable virus was isolated for up to 28 days at 20 degrees C from the surfaces. Conversely, infectious virus survived less than 24 hours at 40 degrees C on some surfaces. Nevertheless, this work indicates that SARS-CoV-2 survival rates are considerably longer than previously believed, so disinfection strategies should be adjusted accordingly.
As the manufacturer of Nemesis eH2O, we have witnessed an enormous increase in demand for both sprayable and foggable product. This is because, whilst hand washing can help protect individuals, effective spraying of touch points is also essential, coupled with the fogging of large spaces to decontaminate surfaces and viral aerosols.”
Sterling Presentation Health was founded in 2015 with a focus on the importance of infection prevention. Working with groundbreaking scientists, the founders developed Nemesis eH2O; a natural antiseptic, anti-bacterial, antiviral and antifungal disinfectant.
Nemesis eH2O technology mimics the human immune system; utilising hypochlorous acid (HOCl) to combat viruses, bacteria and other pathogenic microorganisms.
The process by which Nemesis eH2O is manufactured requires just salt, water and electrolysis. Developed over 12 years, the process delivers a stable form of hypochlorous acid (pH neutral/very weak acid) with a 12-month shelf-life.
Nemesis eH2O is certified as one of the most powerful disinfectants on the market, but remarkably it is environmentally benign; it has no harmful chemicals, no waste product, no preservatives, no colour, no alcohol and no allergic reaction. As a result, Nemesis eH2O can be used as a sanitiser on any surface including sensitive human skin.
Tested and certified as a biocide for the world's most dangerous pathogens, Nemesis eH2O kills 99.9999% of harmful bacteria on contact and is is highly effective against a broad spectrum of pathogens including for example Coronaviruses, Influenza, E. coli, S. aureus, Norovirus, MRSA and C. difficile.
Kampf, G. et al. (January, 2020) Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. Journal of Hospital Infection.
van Doremalen N, et al. (March, 2020) Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. New England Journal of Medicine.
Ratnesar-Shumate S, et al. (July, 2020). Simulated sunlight rapidly inactivates SARS-CoV-2 on surfaces. The Journal of Infectious Diseases.
Fennelly K P. (July, 2020) Particle sizes of infectious aerosols: implications for infection control. The Lancet Respiratory Medicine.
Schuit M, et al. (August, 2020). Airborne SARS-CoV-2 is rapidly inactivated by simulated sunlight. The Journal of Infectious Diseases.
Riddell et al. (October, 2020) The effect of temperature on persistence of SARS-CoV-2 on common surfaces. Virology Journal.
22nd October 2020