Download Coronavirus

Coronavirus:
Virus classification
Group IV
Group:
((+)ssRNA)
Order:
Nidovirales
Family: Coronaviridae
Subfamily: Coronavirinae
Type species
Coronavirus
Coronaviruses are species in the genera of virus belonging to
one of two subfamilies Coronavirinae and Torovirinae in the
family Coronaviridae, in the order Nidovirales.
Coronaviruses are enveloped viruses with a positive-sense RNA
genome and with a nucleocapsid of helical symmetry. The
genomic size of coronaviruses ranges from approximately 26 to
32 kilobases, extraordinarily large for an RNA virus.
The name "coronavirus" is derived from the Latin corona,
meaning crown or halo, and refers to the characteristic
appearance of virions under electron microscopy (E.M.) with a
fringe of large, bulbous surface projections creating an image
reminiscent of the solar corona. This morphology is created by
the viral spike (S) peplomers, which are proteins that populate
the surface of the virus and determine host tropism.
Proteins that contribute to the overall structure of all
coronaviruses are the spike (S), envelope (E), membrane (M)
and nucleocapsid (N). In the specific case of the SARS
coronavirus (see below), a defined receptor-binding domain on
S mediates the attachment of the virus to its cellular receptor,
angiotensin-converting enzyme 2 (ACE2). Some coronaviruses
(specifically the members of Beta coronavirus subgroup A) also
have a shorter spike-like protein called hemagglutinin esterase
(HE).
History
Coronaviruses were first described in the 1960s from the nasal
cavities of patients with the common cold. These viruses were
subsequently named human coronavirus 229E and human
coronavirus OC43.
Diseases caused by coronaviruses
Coronaviruses primarily infect the upper respiratory and
gastrointestinal tract of mammals and birds. Six different
currently known strains of coronaviruses infect humans. The
most recently publicized human coronavirus, SARS-CoV which
causes SARS, has a unique pathogenesis because it causes both
upper and lower respiratory tract infections and can also cause
gastroenteritis.
Coronaviruses are believed to cause a significant percentage of
all common colds in human adults. Coronaviruses cause colds in
humans primarily in the winter and early spring seasons. The
significance and economic impact of coronaviruses as causative
agents of the common cold are hard to assess because, unlike
rhinoviruses (another common cold virus), human coronaviruses
are difficult to grow in the laboratory. Coronaviruses can even
cause pneumonia, either direct viral pneumonia or a secondary
bacterial pneumonia.
In chickens, the infectious bronchitis virus (IBV), a coronavirus,
targets not only the respiratory tract but also the uro-genital
tract. The virus can spread to different organs throughout the
chicken.
Coronaviruses also cause a range of diseases in farm animals
and domesticated pets, some of which can be serious and are a
threat to the farming industry. Economically significant
coronaviruses of farm animals include porcine coronavirus
(transmissible gastroenteritis coronavirus, TGE) and bovine
coronavirus, which both result in diarrhea in young animals.
Feline Coronavirus: two forms, Feline enteric coronavirus is a
pathogen of minor clinical significance, but spontaneous
mutation of this virus can result in feline infectious peritonitis
(FIP), a disease associated with high mortality. Similarly, there
are two types of coronavirus that infect ferrets: Ferret enteric
coronavirus causes a gastrointestinal syndrome known as
epizootic catarrhal enteritis (ECE), and a more lethal systemic
version of the virus (like FIP in cats) known in ferrets as ferret
systemic coronavirus (FSC). There are two types of canine
coronavirus (CCoV), one that causes mild gastrointestinal
disease and one that has been found to cause respiratory disease.
Mouse hepatitis virus (MHV) is a coronavirus that causes an
epidemic murine illness with high mortality, especially among
colonies of laboratory mice.
Prior to the discovery of SARS-CoV, MHV had been the beststudied coronavirus both in vivo and in vitro as well as at the
molecular level. Some strains of MHV cause a progressive
demyelinating encephalitis in mice which has been used as a
murine model for multiple sclerosis. Significant research efforts
have been focused on elucidating the viral pathogenesis of these
animal coronaviruses, especially by virologists interested in
veterinary and zoonotic diseases.
The infection cycle of coronavirus
Replication of Coronavirus begins with entry to the cell which
takes place in the cytoplasm in a membrane-protected
microenvironment. Upon entry to the cell the virus particle is
uncoated and the RNA genome is deposited into the cytoplasm.
The Coronavirus genome has a 5’ methylated cap and a
3’polyadenylated tail. This allows the RNA to attach to
ribosomes for translation.
Coronaviruses also have a protein known as a replicas encoded
in its genome which allows the RNA viral genome to be
transcribed into new RNA copies using the host cells machinery.
The replicas is the first protein to be made; once the gene
encoding the replicas is translated, the translation is stopped by a
stop codon. This is known as a nested transcript. When the
mRNA transcript only encodes one gene, it is monocistronic.
The RNA genome is replicated and a long polyprotein is
formed, where all of the proteins are attached. Coronaviruses
have a non-structural protein called a protease which is able to
separate the proteins in the chain. This is a form of genetic
economy for the virus allowing it to encode the greatest number
of genes in a small number of nucleotides.
Severe acute respiratory syndrome
In 2003, following the outbreak of Severe acute respiratory
syndrome (SARS) which had begun the prior year in Asia, and
secondary cases elsewhere in the world, the World Health
Organization (WHO) issued a press release stating that a novel
coronavirus identified by a number of laboratories was the
causative agent for SARS. The virus was officially named the
SARS coronavirus (SARS-CoV).
The epidemic resulted in over 8,000 infections, about 10% of
which resulted in death. X-ray crystallography studies
performed at the Advanced Light Source of Lawrence Berkeley
National Laboratory have begun to give hope of a vaccine
against the disease "since [the spike protein] appears to be
recognized by the immune system of the host."
Novel human coronaviruses
Following the high-profile publicity of SARS outbreaks, there
has been a renewed interest in coronaviruses among virologists.
For many years, scientists knew about only two human
coronaviruses (HCoV-229E and HCoV-OC43). The discovery
of SARS-CoV added a third human coronavirus.
By the end of 2004, three independent research labs reported the
discovery of a fourth human coronavirus. It has been named
NL63, NL, and the New Haven coronavirus by different
research groups. The three labs are still arguing over which one
discovered the virus first and has the right to name it.
Early in 2005, a research team at the University of Hong Kong
reported finding a fifth human coronavirus in two patients with
pneumonia. They named it Human coronavirus HKU1.
In September 2012, a sixth new type of coronavirus was
identified, initially called Novel Coronavirus 2012, and now
officially Middle East respiratory syndrome coronavirus
(MERS-CoV)
The World Health Organization accordingly issued a global alert
The WHO update on 28 September 2012 said that the virus did
not seem to pass easily from person to person. However, on May
12, 2013, a case of contamination from human to human in
France was confirmed by the French Ministry of Social Affairs
and Health. In addition, cases of person-to-person transmission
have been reported by the Ministry of Health in Tunisia. Two
confirmed cases seem to have caught the disease from their late
father, who became ill after a visit to Qatar and Saudi Arabia.
By Oct. 30 2013, there were 124 cases and 52 deaths in Saudi
Arabia. After the Dutch Erasmus Medical Centre sequenced the
virus, the virus was given a new name, Human Corona VirusErasmus Medical Centre (HCoV-EMC). The final name for the
virus is: Middle East respiratory syndrome coronavirus (MERSCoV).
Listing of human coronaviruses


Human coronavirus 229E
Human coronavirus OC43




SARS-CoV
Human Coronavirus NL63 (HCoV-NL63, New Haven
coronavirus)
Human coronavirus HKU1
Middle East respiratory syndrome coronavirus (MERSCoV), previously known as Novel coronavirus 2012 and
HCoV-EMC..
Coronaviruses in veterinary medicine
Coronaviruses have been recognized as causing pathological
conditions in veterinary medicine since the early 1970s. Except
for avian infectious bronchitis, the major related diseases have
mainly an intestinal location.
Listing of coronaviruses in domestic animals
(Listed following their estimated economical importance)






Infectious bronchitis virus (IBV) causes avian infectious
bronchitis.
Porcine coronavirus (transmissible gastroenteritis
coronavirus of pigs, TGEV).
Bovine coronavirus (BCV), responsible for severe profuse
enteritis in of young calves.
Feline coronavirus (FCoV) causes mild enteritis in cats as
well as severe Feline infectious peritonitis (other variants of
the same virus).
the two types of canine coronavirus (CCoV) (one causing
enteritis, the other found in respiratory diseases).
Turkey coronavirus (TCV) causes enteritis in turkeys.


Ferret enteric coronavirus causes epizootic catarrhal
enteritis in ferrets.
Ferret systemic coronavirus causes FIP-like systemic
syndrome in ferrets.
Another new veterinary disease, Porcine epidemic diarrhea
virus, has emerged around the world. Its economic importance is
as yet unclear, but shows high mortality in piglets.
The most recent common ancestor of the coronovirus has been
placed at 10,000 years before the present. They may be
considerably older than this.
Another estimate places the most recent common ancestor
(MRCA) of all coronaviruses ~8100 BC. The MRCA of Alpha
coronavirus, Beta coronavirus, Gamma coronavirus, and Delta
coronavirus have been placed at ~2400 BC, ~3300 BC, ~2800
BC and ~3000 BC, respectively. It appears that bats and birds,
the warm blooded flying vertebrates, are ideal hosts for the
coronavirus gene source with bats for alpha coronavirus and
beta coronavirus and birds for gamma coronavirus and delta
coronavirus, to fuel coronavirus evolution and dissemination.
Bovine coronavirus and canine respiratory coronavirus diverged
from a common ancestor in 1951. Bovine coronavirus and
human coronavirus OC43 diverged in 1899. Bovine coronavirus
diverged from the equine coronavirus species at the end of the
18th century.
Another estimate suggests that human coronavirus OC43
diverged from bovine coronavirus in 1890.
The MRCA of human coronavirus OC43 has been dated to the
1950s.
Middle East respiratory syndrome coronavirus although related
to several bat species appears to have diverged from these
several centuries ago.
The most closely related bat coronavirus and the SARS
coronavirus diverged in 1986.
A path of evolution of the SARS virus and keen relationship
with bats have been proposed. The authors suggest that the
coronaviruses have been coevolved with bats for a long time and
the ancestors of SARS virus first infected the species of the
genus Hipposideridae, subsequently spread to species of the
Rhinolophidae and then to civets and finally to humans.
Alpaca coronavirus and human coronavirus 229E diverged
before 1960.