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The global public health emergency of COVID-19 pandemic disease caused by severe acute respiratory
syndrome coronavirus 2 (will be referred as SARS-CoV-2 hereafter) has been unfolding rapidly that
emerged in Wuhan, China and has now spread to at least 180 countries. Detailed investigations found that
SARS-CoV in 2003 was transmitted from civet cats to humans and MERS-CoV in 2012 from dromedary
camels to humans.1 The genetic sequence of the SARS-CoV-2 enabled the rapid development of point-of-
care real-time RT-PCR diagnostic tests specific for SARS-CoV-2 which is based on full genome sequence
data on the Global Initiative on Sharing All Influenza Data [GISAID] platform.2 Though in a scorching
pace, the scientist of China shared its genome sequence, it is the Australian scientists who have for the
first time recreated the virus.3
It is suggested that even though patients of all ages are susceptible to this
disease, individuals developing critical illness were older with greater number of co morbid conditions.
1.1 Historical Background
On 31 December 2019, World Health Organization (will be referred as WHO hereafter) was alerted about
an outbreak of several cases of pneumonia in Wuhan City, Central Hubei Province of China raising
concern since the affected patients were geographically linked with a local wet market as a potential
source with 12% risk of death.
5 On 7 January 2020, Chinese authorities confirmed identification of a
novel coronavirus, named “2019-n CoV” from the family of viruses that include SARS-CoV and MERS-
CoV.
6 China reported its first death of a 61 year old patient from SARS-CoV-2 on 11 January 2020.
Further, on 20 January 2020, WHO situation report detailed the first confirmed cases outside China in
Thailand, Japan and South Korea. However, on 31 January 2020, WHO declared the outbreak a global
public health emergency as more than 9,000 cases were reported from all over the world. The Diamond
Princess Cruise ship on 1 February 2020 with 3,711 people on board was found to have the epidemic of
SARS-CoV-2.
7 On 9 February 2020, the death toll in mainland China surpassed number of fatalities from
SARS outbreak in 2003.8
Italy on 24 February 2020 became the worst-hit country in Europe by this virus.9
On 28 February 2020, Iran reported 34 deaths out of 388 confirmed coronavirus cases, making it the
country with the highest number of deaths from the virus outside China. President Trump of USA signed
an $8.3 billion emergency spending package on 6 March 2020 to combat the coronavirus outbreak, as the
number of global cases hit 1,00,000.10 Henceforth, on 11 March 2020 WHO made the assessment of
Coronavirus as pandemic. Spain recorded a spike of nearly 2,000 new cases on 14 March 2020.
11 Italy on
16 March 2020 announced that confirmed cases rose to nearly 28,000, an increase of more than 3,000
from the day before, while the death toll hit 2,158.12
1.2.Epidemiology
So far, as on date 23 March 2020, 3,39,039 globally confirmed cases13 are reported and 81,093 confirmed
cases from China but 3,270 deaths making China “Very High” under WHO risk assessment.14 Between
lockdowns and quarantines, the COVID-19 epidemic in China peaked and plateaued by early February, to
even decline from there. Person-to-person transmission of SARS-CoV-2 in hospital and family settings
may be suggested, as reports of infected travellers in other geographical regions surfaced.
15 In India, 415
cases are reported till 23 March 2020, according to Ministry of Health & Family Welfare. Therefore, the
Government of India has asked travellers from China to immediately report to nearest health facility in
case they do not feel well.16
1.3.Causative Agent
SARS-CoV-2 is a type of RNA virus which is zoonotic in origin and it is estimated that Coronavirus
infections are likely to emerge periodically in humans due to frequent cross-species infections and
occasional spillover events.
17 Coronaviruses are a large family of viruses that cause the common cold as
well as more serious respiratory illness. There are six known human coronaviruses which were first
identified in the 1960s from patients with the common cold.
18 The transmission of coronavirus is reported
through respiratory droplets, human contact and fecal-oral route.19 20 21
1.4. Incubation period
Median incubation period is 5.8 days22 with range reported from 2.1 days to 11.1 days. This implies that
under conservative assumption, length of quarantine or active monitoring can be up to 14 days.23
2. Pathogenesis
The pathological features of SARS-CoV-2 of family Coronaviridae measuring from 60 to 140 billionths of
a metre across, having median R0 2.79
24 with early outbreak data following exponential growth25 have
been shown to greatly resemble those seen in SARS and MERS coronavirus infection.26 27 First described
in 1960s, the coronavirus gets its name from a distinctive corona or “crown” of sugary-proteins projecting
from envelope surrounding the particle. Following the entry of coronavirus into the cell, the uncoated
particle and the RNA genome is deposited into the cytoplasm. The coronavirus RNA genome has a 5′
methylated cap and a 3′ polyadenylated tail, which allows the RNA to attach to ribosomes for translation.
Coronaviruses also have a protein known as a replicase encoded in its genome which allows the RNA
viral genome to be transcribed into new RNA copies using the host cell's machinery.
28 Coronaviruses have
a non-structural protein – a protease – which can separate the proteins in the chain.29 30 The excess
production of type 2 cytokines and an age dependant defect in T-cell and B-cell function could lead to a
deficit in control of viral replication and more prolonged proinflammatory responses, potentially leading
to a poor outcome in patients of COVID-19.31 The main pathogenesis of SARS-CoV-2 as a respiratory
system targeting virus is severe pneumonia, RNAaemia and acute cardiac injury. In a first-hand data
reported from Hospital of China, it was found that, by Jan 2, 2020, 41 laboratory- confirmed SARS-CoV-
2 infection admitted hospital patients had a higher plasma level of IL2, IL7, IL10, GSCF, IP10, MCP1,
MIP1A, and TNFα.32
2.1. Histopathology
From the histopathological data obtained on the lungs of two patients undergoing lung lobectomies for
adenocarcinoma who were retrospectively found to have had SARS-CoV-2 infection at the time of
surgery, the lungs of both 'accidental' cases showed oedema, exudates as large protein globules, vascular
congestion combined with inflammatory clusters of fibrinoid material, multinucleated giant cells and
hyperplasia of pneumocytes.33
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