In-Depth Overview of Viral Gastroenteritis: A thorough introduction to the causes, transmission, and epidemiology of viral gastroenteritis, with a focus on key viruses like Norovirus, Rotavirus and Adenovirus.
Part 1: Gastroenteritis:
• One of the most common diseases in mankind
• 200 million people suffer from diarrhoea every day!
• Worldwide mortality - 4-10 million people per annum
11,000 per day; compare to measles 4,000, pneumonia 6,000, malaria 2,000
• Second most common cause of child death globally
Agents that commonly cause gastrointestinal illness:
Most deaths occur in developing countries due to limitation in access to fresh, clean water
and poor hygiene.
Gastroenteritis viruses:
• Viral gastroenteritis - inflammation of the lining of the stomach, small and large
intestine. "stomach flu" ----> misnomer
• Most people recover without problems, but compilations derive from dehydration.
Fluid intake needs to be higher than the lost through vomiting and diarrhoea.
• Highly contagious and extremely common.
Many viruses infect via the gastrointestinal tract, but disseminate elsewhere and do not
cause gastroenteritis. Not all viruses that enter GI tract cause pathogenesis.
Enteroviruses = misnomer
For gastroenteritis viruses, the gut has to be both the portal of entry and the target tissue:
○ Replicate in the gut and remain in the gut
○ Induce symptoms in the gut, usually diarrhoea and/ or vomiting.
They spread via the oral-faecal route.
→ Usually enter via food and water -----> food poisoning.
→ Excreted in faeces: poor hygiene, sanitation, clean water availability etc.
Can cause severe outbreaks. These are not normally serious as long as fresh drinking water is
available (developing countries).
The majority do not grow well (if at all) in tissue culture and remain poorly characterised.
Diagnostic/ Detection tools:
• Most gastroenteritis viruses do not grow in laboratory settings.
• Most gastroenteritis viruses infect at very low doses (10-100 vp)
• Viruses are rarely detectable in food (only exception the Bivalbia shellfish)
Viral Gastroenteritis Page 1
, • Viruses are rarely detectable in food (only exception the Bivalbia shellfish)
Shellfishes are filter feeders, they feed by filtering water through their gills and collect the
phytoplankton. When these animals come into contact with water that has been
contaminated with faecal matter from individuals infected with these viruses. The viruses will
then be retained in the gills and the gills help to concentrate the virus.
• Routine food screening is not feasible and most food contaminations are identified
retrospectively from patients' clinical samples.
• Electron microscopy
• Genomic/ NAAT tests
→ RT-PCR on the viral genome
• Cell culture
Not available for these viral types
• Methods available lead to underestimate of gastroenteritis infections
• None of these methods informs about infectivity!
• Best is to prevent: HACCP guidelines for handling and safety management of food.
Part 2: Gastroenteritis
General features of GE viruses:
All these viruses are non-enveloped because they developed resistance to environmental
inactivation. This is also the reason why these viruses survive in harsh environment (eg. Very
low PH) and get transmitted through gastrointestinal tract.
Astroviruses (AstV):
• Non-enveloped, 30nm icosahedral virus with a peculiar 5-6 pointed, star like
appearance.
• 7kB, positive ssRNA ----> group IV
• Worldwide distribution
• Transmitted through the oral-faecal route (winter)
• Infects epithelial cells of the intestinal tract (small intestine), inducing mostly diarrhoea.
• Affects mostly 2 groups: young children and elderly, institutionalised patients.
• Determinants of immunity not really well understood, but generated immunity is long-
lasting (although reduces with age).
• >80% children between 5-10 years-old have antibodies against AstV
• Diagnosis by EM, ELISA or NAAT (sequence variability)
Adenoviruses (AdV):
• Non-enveloped, icosahedral viruses with large DNA genome (~36-38kB)
→ Group 1 Baltimore classification
Viral Gastroenteritis Page 2
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