Introduction
Coronaviridae family is a single-strand, positive-sense,
enveloped RNA virus family(Su et al., 2016) that can be found
circulating in a wide range of avian and mammal species hosts.(Cavanagh,
2007; Ismail, Tang, & Saif, 2003) In December 2019, a patient was found
to have pneumonia caused by an unknown betacoronavirus. By using
unbiased sequencing of the sample from the patient, a novel coronavirus
was determined. According to the latest official name by the
International Committee on Taxonomy of Viruses (ICTV), it should be
called Severe Acute Respiratory Syndrome Coronavirus
2,
SARS-CoV-2 in abbreviation. Then within the same month, in late
December, there are already been a crowd of patients that had been
diagnosed with infecting the pathogen. (W. M. H. Commission, 2019; Zhu
et al., 2020) The widely believed origin, seafood wholesale market in
Wuhan, Hubei Province, China, was proven wrong according to the official
announcement.(rfi, 2020) The origin of the virus is still a mystery.
SARS-CoV-2 is identified to be a betacoronavirus that belongs to the
subgenus sarbecovirus of Coronaviridae family (Beta-CoV lineage
B) based on the Phylogenetic analysis.(David S. Hui et al., 2020; R. Lu
et al., 2020; Wong, Li, Lau, & Woo, 2019) Therefore, similar to other
coronaviruses, it is a
positive-sense
single-stranded RNA (+ssRNA) virus with an envelope, and its granules
are round or oval in shape with a diameter of 50 to 200 nm.(Zhe, 2020)
Typical betacoronavirus structures (S gene, E gene and M gene etc.) was
found by Zhu et al.(Zhu et al., 2020) and Zhou et al.(P. Zhou et al.,
2020a) Notably, S (spike) protein is one of the main proteins of the
virus with its gene coding always used for virus typing.(Zhe, 2020) The
protein itself could be divided into two domains, S1 domain and S2
domain. Each domain is responsible for different functions, where S1
domain is responsible for receptor binding and S2 domain is responsible
for cell membrane fusion.(He et al., 2004; F. Li, 2016) The protein also
plays a key role in determining the host’s ability of transmission and
tropism.(G. Lu, Wang, & Gao, 2015; Q. Wang, Wong, Lu, Yan, & Gao,
2016)
It has been confirmed that, through numerous reports from all over the
world, the virus has a person-to-person transmission route.(Chan et al.,
2020; Rothe et al., 2020; Wired., 2020; Zhe, 2020) The sources of
infection seen so far are mainly patients with new coronavirus
infection. Asymptomatic infection can also be a source of infection.(N.
H. Commission, 2020) Respiratory droplets and close contact transmission
are the main routes of transmission. There is the possibility of aerosol
transmission in a relatively closed environment for a long-time exposure
to high concentrations of aerosol. Population in crowdedness is also
under risk is generally susceptible.(N. H. Commission, 2020)
According to the up-to-date studies, the
basic
reproduction number (R0) of the virus has been estimated to be 1·4 -
3·9 with the incubation period is about 1-14 days, mostly 3-7 days, and
an average 4·8 days.(Q. Li et al., 2020; Riou & Althaus, 2020; Rothe et
al., 2020) The fatality rate is about 2% with fever, dry cough and
fatigue as the main manifestations. Its viral diagnostic method had
already been developed basing on PCR and RT-PCR.(Corman et al., 2020;
Jonsdottir & Dijkman, 2016; Liu et al., 2019; Zhu et al., 2020) Since
the E gene and the RdRp gene are comparatively more sensitive, they were
chosen for further evaluation for detection.(Corman et al., 2020) Whist,
development of its vaccine is also already on the way.(Steenhuysen,
2020)
As of 12 April 2020, the Coronavirus disease 2019 (COVID-19) Situation
Report from WHO(WHO, 2020) reported that 1,610,909 confirmed (89,657
new) and 99,690 deaths (6,892 new) cases globally, and 83,369 confirmed
(64 new) in China with 3,349 deaths (4 new). These figures show that
China has roughly controlled the epidemic, but the situation in the rest
of the world is becoming less and less optimistic as there are more
concentrated outbreaks are taking place.
Since considerable studies had
already been carried out based on the analysis of SARS-CoV-2’s genome
sequence and its comparison with that of the other SARS-like virus, let
us review in detail and, hopefully, they might provide us with some key
features for answering some of the crucial questions relating to its
origin, epidemiology, and treatment to
better contain the virus. Basing
on that, clues on how to develop a fast and accurate viral diagnostic
method and the way of treating it may also be provided.