Biology Reference
In-Depth Information
Groups 1 and 2 infect mammalian hosts while Group 3 infects only
avian hosts.
In animals, coronavirus infections can lead to virulent multi-systemic
diseases. For example, in pigs, the porcine transmissible gastroenteri-
tis virus (TGEV) causes respiratory and enteric infections; in mice, the
mouse hepatitis virus (MHV) causes respiratory, enteric and neuro-
logic infections as well as hepatitis.
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In humans, coronaviruses were associated with mild diseases until
the appearance of the SARS coronavirus, which causes severe, often
life-threatening, disease. Most human coronaviruses cause a mild,
upper respiratory tract infection. They are transmitted via the aerosol
route and direct as well as indirect contact. The incubation period of
the virus is about three days, leading to the symptoms of a common
cold: fever, runny nose, cough and malaise. The disease is resolved
within a few days. An exceptional case is the SARS virus, a newly dis-
covered human coronavirus.
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The outcome of SARS infection varies
from a mild illness to a more severe disease leading to respiratory fail-
ure and death. Phylogenetic analysis suggests that the SARS virus has
split off from the Group 2 coronaviruses.
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The Caliciviridae Family
The
Caliciviridae
family is comprised of viruses that are known to cause
disease in humans and other animal species.
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The family is divided into
four genera:
Vesivirus
,
Lagovirus
,
Norovirus
, and
Sapovirus
.
9
Caliciviruses
have a single-stranded, non-segmented, positive-sense RNA genome of
approximately 7.7-8.5 kB. Family members encode two or three ORFs,
the arrangements of which differ between genera. The viruses have a
non-enveloped, icosahedral capsid composed of a single protein type.
The Norwalk virus (genus
Norovirus
) capsid protein has two major
domains, S and P. The S domain forms the inner shell while the P
domain forms arch-like structures that extend outward from the shell.
10
Caliciviruses infect different species and cause remarkably differ-
ent diseases in their hosts.
9
The ability to correlate the type of disease
caused by the virus to features in its genomic sequence is some-
thing that the PATRIC project aims to enable. In swine, the vesicular
