The Operating Theatre Journal November 2020

Covid-19 What have we learned about the virus, so far?
Author: Adrian Gee-Turner
Summary
As the pandemic progressed,
our understanding of the virus
that causes Covid-19 grew, and
this has influenced the guidance
on transmission prevention
measures such as face masks,
social distancing, hand washing
and disinfection. Whilst a few
grey areas persist, such as the
degree of challenge presented
by aerosolised virus, a number
of conclusions are emerging. For
example:
• 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 (<5 μm)
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 9 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
9 days; it also mentioned that
temperatures of 30 DegC 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 DegC, 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 titer (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.
Airborne transmission
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
(<5 μm) 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
DegC, 30 DegC and 40 DegC 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 DegC from the
surfaces. Conversely, infectious
virus survived less than 24 hours
at 40 DegC 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.
References:
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.
For further information, contact:
Sterling Presentation
Health Limited
Royal Bank Chambers
Melrose
TD6 0PN
Email: info@nemesis-eH2O.com
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