Biology Reference
In-Depth Information
exanthema virus (VESV) (genus
Vesivirus
) causes vesicles on the snout
and hooves. In cats, the feline calicivirus (FCV) (genus
Vesivirus
) causes
conjunctivitis, ulcers, limping, and respiratory disease. The
Lagovirus
species cause extensive hepatic necrosis in rabbits and hares. In
humans, the
Noroviruses
and the
Sapoviruses
are transmitted primarily
by the fecal-oral route and are the most important causes of epidemic
nonbacterial gastroenteritis. The virus has a mean incubation period
of about 24 hours, with the illness lasting from 24 to 48 hours.
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Norwalk virus gastroenteritis is characterized by nausea, vomiting and
diarrhea; the disease is usually self-limiting.
Hepatitis A Virus
The hepatitis A virus (HAV) is the only member of the genus
Hepatovirus
(
Picornaviridae
family).
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The HAV genome is a single-
stranded, non-segmented, positive-sense RNA molecule of size 7.4
kB. It contains just one gene that encodes a large polyprotein of 2227
amino acids that is proteolytically cleaved to form ten smaller, func-
tional proteins. The genomic RNA molecule is uncapped but
polyadenylated, and it has a viral protein (Vpg) covalently attached to
its 5
end. HAV has a non-enveloped, dodecahedral capsid that is
composed of four types of structural polypeptides. The genomic RNA
molecule, along with the covalently linked Vpg, forms the inner core
of the virion.
The virus causes disease in humans and several primate species.
Transmission occurs mainly via the fecal-oral route by the ingestion of
food or water contaminated with infected feces. The course of HAV
infection is highly variable, ranging from asymptomatic infection to
acute disease. The ability to correlate symptoms of the infection to
features in its genomic sequence is something that the PATRIC project
aims to enable. The disease has four progressive stages: incubation,
prodromal, icteric, and convalescent. The incubation period ranges
from 10 to 50 days, followed by fatigue, fever, nausea and vomiting.
In the icteric stage, abnormally high bilirubin levels cause a discol-
oration of the mucous membranes, skin and conjunctivae; the patient
discharges dark, golden-brown urine and pale stools. Most patients
′
