The novel coronavirus disease (COVID-19), caused by SARS-CoV2 in 2021, is a tsunami like coronavirus outbreak relative to the previous outbreaks involving older coronavirus or Swine flu (h1n1) or Spanish flu. With the number of COVID-19 cases now exploding worldwide, it is certain that transmission of SARS-CoV-2 is very high possibly airborne (aerosol droplet) and there are diverse spectrum of disease severity. The biological issues like a genetic susceptibility and variability in the response to the virus are still being elucidated. Controlling current rates of infection and combating future waves require a better understanding of the routes of exposure to SARS-CoV-2 and the underlying genomic susceptibility to this disease. How individuals respond to SARS-CoV-2 exposure is becoming better understood in a global sense, but differences in the vulnerability of individuals to infection and in the spectrum of COVID-19 symptoms remain to be understood. It is known that advanced age and pre-existing conditions (e.g. metabolic, cardiovascular, pulmonary, and renal diseases) render a person

1. Journal of The Association of Physicians of India ■ Vol. 69 ■ May 2021 11
and natural infection immunity. Various
factors driving SARS-CoV-2 variant
evolution, include specific mutations,
examine the risk of further mutations,
and consider the experimental studies
needed to understand the threat these
variants pose. Plante et al. examine
SARS-CoV-2 variants including B.1.1.7
(UK), B.1.351 (RSA), P.1 (Brazil), and
B.1.429 (California).3
Some mutations
can enhance virulence to make it more
invasive as well as severity. Most have
till date not been documented linked
to severity but possible links with
transmissibility can’t be ruled out.
Vaccine is the fourth pillar after
the covid appropriate behaviour of
mask, distancing and sanitizing. The
vaccine primary goal is to protect the
most vulnerable from death and severe
diseases. These are all early generation
rapidly developed vaccines which are
all in Emergency use authorisation
(EUA) mode. India is part of the
global alliance for vaccine and has
risen above vaccine nationalism by
exporting vaccine fulfilling its global
obligations. We need to vaccinate
all our vulnerable groups which can
succumb to c o v i d 19 independent
of the age but must follow vaccine
discipline. Even after vaccination with
full doses we need to mask, avoid
crowds or poorly ventilated spaces,
distance and sanitize. Post vaccine
covid 19 needs investigation to study
the phenomenon of immune escape or
efficacy. Also the severity of the disease
and phenotype of post vaccine COVID
19 needs to be studied. We should never
unmask while speaking, when eating
try to avoid public spaces in crowds
but eat in safe zone and ensure that we
don’t unmask as much as possible. We
need to use safer masking strategies
like doubling up, using mask braces,
ensure its tight and well covered. There
COVID 19 in India: Waves, Variants of Concern, Airborne
Transmission
Shashank R Joshi
Member, Maharashtra Covid-19Task Force, Consultant
Endocrinologist,LilavatiHospital,Mumbai,Maharashtra
e d i t o r i a l
The novel coronavirus disease
(COVID-19), caused by SARS-CoV-
2 in 2021, is a tsunami like coronavirus
outbreak relative to the previous
outbreaks involving older coronavirus
or Swine flu (h1n1) or Spanish flu.
With the number of COVID-19 cases
now exploding worldwide, it is certain
that transmission of SARS-CoV-2 is
very high possibly airborne (aerosol
droplet) and there are diverse spectrum
of disease severity. The biological
issues like a genetic susceptibility
and variability in the response to
the virus are still being elucidated.
Controlling current rates of infection
and combating future waves require
a better understanding of the routes
of exposure to SARS-CoV-2 and the
underlying genomic susceptibility
to this disease. How individuals
respond to SARS-CoV-2 exposure
is becoming better understood in
a global sense, but differences in
the vulnerability of individuals to
infection and in the spectrum of
COVID-19 symptoms remain to be
understood. It is known that advanced
age and pre-existing conditions (e.g.
metabolic, cardiovascular, pulmonary,
and renal diseases) render a person
more vulnerable to severe COVID-19.1
However, a surprising observation
emanating from the current pandemic
is the rate of hospitalization of younger,
ostensibly healthy individual especially
in the newer waves in 2021. Is there a
vulnerability index of COVID 19 for
India? What makes some people more
vulnerable than others to SARS-CoV-
2? What role do gene networks play in
determining or influencing efficiency
of infection, the immune response to
infection, or the severity of COVID-19
symptoms? Our understanding of
genetic susceptibility to SARS-CoV-2
infection and the severity of COVID-19
is still in its infancy.1
In addition to the
genomics research, attention needs to
be paid to the spread of the virus and
how it can be prevented in India by
breaking the chain of transmission.
What makes some SARS-CoV-2
infected individuals extremely sensitive
to the development of acute respiratory
distress syndrome (ARDS) while
others are asymptomatic.1
The impact
of ACE2 gene and its protein on viral
entry with TMPRSS as well as furin is
well known. Genetic polymorphisms
of either ACE2 or TMPRSS or furin
can have impact on cellular invasion
to facilitate rapid entry. Could it lead
the virus bypass nose or throat and
enter the lung or could it be more
virulent are unanswered questions
which are now being investigated.
Variations in COVID-19 severity might
be classified as (a) asymptomatic, (b)
symptomatic but no hospitalization
required, and (c) severely symptomatic
with hospitalization urgently indicated.
Elucidation of alleles of relevant genes
associated with these three levels of
severity to viral response might aid
clinicians in dealing with possible
future waves of this pandemic.1
The second surge in India started
very quietly from less exposed
population clusters in some districts
from where it’s rapidly spread to rest
of India. Clearly in the second wave we
are seeing a faster transmissible strain,
but of unknown virulence.2
Currently
the Indian variants of concern are being
investigated by genome and public
health experts to delineate if it’s an
imported strain like UK, South African
or Brazilian one or is a home grown
mutant. The initial data suggested by
Indian research agencies have identified
a double mutant of E484Q and L454R
strains. The public health strategy will
still be the same. Worldwide more than
a million sequences have been done and
some have been designated as “Variants
of concern”. CDC classifies them as
B.1.1.7(British), P.1(Brazil), B.351(South
African) American (California, New
York), and Indian (B.1.617). SARS-CoV-
2 variants bring concerns for increased
spread and escape from both vaccine

2. Journal of The Association of Physicians of India ■ Vol. 69 ■ May 2021
12
has to be zero tolerance for violators
of c o v i d norms, behaviour and
protocols and we need to have a single-
minded determination to conquer and
decontaminate this nasty virus. We
need to be proactive to clear the virus
from our environment using mind and
body strategies and build a strong
covid free India.2
The contribution of aerosol exposure
to the transmission of SARS-CoV-
2 has been under scrutiny. Many
global scientists have emphasized
that infected individuals represent
emission sources of aerosol generated
by routine behaviours—such as
breathing, speaking, singing, coughing,
sneezing, and resuspension activity—
all of which might be capable of
transmitting disease.1
SARS Cov2 is a
typical respiratory RNA virus which
spreads via aerosol generation. As
with any infectious respiratory disease,
an infected individual can release
aerosols and droplets containing SARS-
CoV-2 by coughing or sneezing. The
transmission efficiency of SARS-CoV-2
has proved to be high, with reported
reproductive numbers greater than
that of the 2009 H1N1 influenza virus.4
SARS-CoV-2 have virus-containing
aerosols and droplets can lead to short-
range airborne transmission (~ 6 ft).
Such aerosols (< 10-μm diameter )
and droplets (> 10-μm diameter) can
promote infection through (i) deposition
on surfaces and subsequent hand-
to-mouth/nose/eye transfer and (ii)
inhalation. While suspended airborne
droplets can persist in the air for several
minutes, the smaller aerosols do not
rapidly settle and can persist for longer
durations (~ minutes to hours). Once
airborne, the characteristics of aerosols
generated by cough or sneeze are
dynamic, notably decreasing in size due
to evaporative loss of water depending
on ambient humidity and temperature
levels. As the size of aerosols decrease,
their ability to disperse in the air is
enhanced. Therefore, inhalation of
aerosol-borne SARS-CoV-2 is likely to
be a relevant mode of viral infection,
with the range of aerosol transmission
extending beyond 6 ft of an infected
individual. Beyond coughing and
sneezing, normal speech and breathing
can also generate aerosol. The size of
aerosol generated by speaking and
breathing is similar, ranging from
0.75 to 1.1 μm, but is notably smaller
than those generated by coughing or
sneezing, i.e. ~ 5 μm. The concentration
of aerosol released by the combination
of speaking and breathing for more
than 4 min is equivalent to the amount
of aerosol emitted for 30 s of singing
or coughing.5
The volume of speech
can further influence aerosol release,
leading to variations in emission rates
between individuals that may impact
their capacity for viral transmission;
this is relevant, in particular, for
infected individuals that are pre-
symptomatic or have asymptomatic
illness.1
The detection of SARS CoV2 in air
both in indoor and outdoor spaces
is now better understood and linked
to virus viability in air; factoring
both temperature and humidity. The
northern hemispheric, temperate
reginal waves in winters and the
tropical Indian wave in hotter, humid
environments merits scientific scrutiny.
The high transmissivity of the virus
suggests that a low dose might be
sufficient to infect an individual;
however, such studies have yet to
evaluate the infectious dose of SARS-
CoV-2.1
Until scientific evidence
emerges, it is useful for individuals
to follow approaches that minimize
their risk of infection by reducing
their exposure level and duration of
exposure. The combined use of masks
and physical distancing can be effective
approaches for decreasing exposure
to airborne forms of SARS-CoV-2.
Avoiding or minimizing the time in
contact with these potential aerosol
exposures would also be a critical
parameter in lowering risk. Common
approaches for mitigating airborne
exposures include (i) identification
of emission sources, (ii) prevention
of viral shedding and inhalation
exposure, and (iii) environmental
controls. The key area of environmental
controls leverages evidence of reduced
exposures by improving ventilation,
utilization of portable filtration
devices, or other aerosol inactivation
technologies, and cleaning practices to
reduce exposure from resuspension.
This topic of environmental controls
is broad and complex and guidance
prepared by the American Society
of Heating, Refrigerating and Air-
Conditioning Engineers (ASRHAE)
and other recent papers focused on
indoor ventilation and environmental
controls.5,6
Masking is the primary face covering
which offer protection from virus
laden aerosol or droplets with the gold
standard n95 mask capable of filtering
more than 99% of airborne aerosols
compared to filtration efficiencies
of surgical masks (~ 75%) and cloth
coverings (~ 67%) that afford inward
protection against for aerosols sized
between 0.02 and 1 μm.8
A range of face
coverings is available—including N95
respirator masks, surgical masks, and
cloth coverings, each offering different
efficiencies for inward protection
(i.e., PPE) and outward protection
(i.e., source control) from virus-laden
aerosol and/or droplets.9
There is a need to double mask and
do innovation in design and filtration
efficiency of cloth masks both for adults
and children which will be the key and
as important as vaccine development to
prevent the spread of the virus. While
promoting the use of face coverings
by the public, it is also essential to
ensure cleaning protocols prior to
reuse, and to reinforce the importance
of continued physical distancing to
prevent individuals from having a false
sense of security. The real threats of
recurrent waves of the pandemic loom
large and the key will be behaviour
change and preventive strategies
including vaccine, identification of
vulnerable groups and avoidance of
viral contamination.
References
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CS, Nebert DW, Reichardt JKV, Thompson DC, Vasiliou V.
COVID-19 vulnerability: the potential impact of genetic
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32398162; PMCID: PMC7214856.
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