5. Viral Infections of the GI Tract

5. Viral Infections of the GI Tract - Viral Infections of...

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Viral Infections of the Gastrointestinal Tract “A spew with a view” A spew with a view” Gastrointestinal Tract Gastrointestinal Tract Defences Defences • Saliva (contains enzymes) • Mucous membranes (sticky) • Gastric juice - low pH, enzymes, mucous • Local IgA (antibody found in mucous membranes) • Lymphoid tissue - Peyer's patches • Normal flora (bacteria help to absorb and destroy virus particles) Characteristics of Gastrointestinal Viruses a) Occur in outbreaks b) Most are more common during winter months c) Short incubation period d) Short duration of symptoms e) Cause more serious infections in very young and elderly Viruses which cause Viruses which cause Gastrointestinal Infections Gastrointestinal Infections Rotavirus (common cause of viral diarrhoea in children) Norwalk (common cause of viral diarrhoea in adults) • Adenovirus • Enteroviruses (cause diarrhoea during summer and fall months) • Others - Calicivirus, astrovirus, coronavirus, torovirus Rotavirus Rotavirus • Reovirus Family • Non-enveloped RNA virus • Wheel-shaped • Six serotypes A - F, A is most common
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Rotavirus Rotavirus E pidemiology • Most children infected by age 3 (world-wide) • Commonest in late winter, early spring • Faecal-oral spread • Virus survives well on surfaces, hands, fomites (inanimate objects) • Outbreaks occur in day-care centres, paediatric hospitals • Nursing home outbreaks have been documented Rotavirus Rotavirus Clinical Clinical • Incubation period - 48 hrs. • Vomiting, watery diarrhoea, fever - lasts 3-7 days • Respiratory symptoms may also occur in children • Infants, elderly may rapidly become dehydrated (particularly serious in developing countries) Rotavirus Rotavirus Diagnosis Diagnosis • Rapid (20 min) direct antigen tests available - detect presence of virus protein in stool specimen • Electron microscopy (direct visualization of virus in stool specimen) Rotavirus Rotavirus Treatment Treatment • Re-hydration most important (ORT) • No specific anti-viral drug available • Rotavirus vaccine was licensed in U.S. in 1999, but problems with adverse effects - vaccine was withdrawn from the market Norwalk Norwalk • Calicivirus Family • Small, non-enveloped RNA virus • Multiple antigenic types • Other Norwalk - like viruses in the same family (Snow Mountain virus, Hawaii agent, Toronto virus) cause the same symptoms
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Norwalk Norwalk Epidemiology Epidemiology • Widespread winter outbreaks (winter vomiting disease) • Adults primarily affected - nursing home patients most severely • Rapid spread from person to person via hands (faecal-oral), fomites • May be associated with contaminated water and shellfish (sewage contamination) • Can shut down cruise ships Norwalk Norwalk Clinical Clinical • Short incubation (24-48 hours) • Severe nausea, cramps, vomiting,
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5. Viral Infections of the GI Tract - Viral Infections of...

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