Viral Diarrhea

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Viral Diarrhea

• Chris E. Forsmark, M.D.
• Division of Gastroenterology, Hepatology, and
  Nutrition

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Virus Types

• Viral gastroenteritis
• Rotavirus
• Caliciviruses
• Adenovirus
• Astrovirus
• Others (Torovirus, coronavirus,pestivirus)
• Viral colitis
• Cytomegalovirus

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Magnitude of the Problem
Bull WHO 1992
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Magnitude of the Problem

• Developing countries
• 2.6 episodes/child/year in children lt 5
• 700 million episodes/year
• 3-5 million deaths/year
• United States
• Approx 180,000 hospitalizations/year in children
  lt 5
• Mortality rare

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Viral Gastroenteritis in Children
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Rotavirus

• Discovered in 1973
• Worldwide distribution
• All children exposed by age 4-5
• Double stranded RNA virus
• Several groups (A-E vs G-P)
• Most common cause of viral diarrhea
• 35 hospitalized, 10 community

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Rotavirus
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Rotavirus
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Rotavirus
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Rotavirus structure
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Transmission of Rotavirus

• Fecal-oral
• Contaminated water supplies
• Poor hygiene
• Food
• Fomites

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Rotavirus Clinical Syndromes

• Childhood gastroenteritis
• Endemic in tropics
• Winter in temperate zone
• Outbreaks
• Day care centers
• Hospitals
• Immunocompromised adults

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How does Rotavirus cause diarrhea?

• Injures intestinal epithelium
• Malabsorption
• Increases secretion by epithelium

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Diarrhea Classification

• Pathophysiology
• Osmotic
• Secretory
• Exudation
• Abnormal motility
• Duration
• Acute (lt 6 weeks)
• Chronic (gt 6 weeks)

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Osmotic diarrhea

• Def Increased amounts of poorly absorbed,
  osmotically active solutes in gut lumen
• Interferes with reabsorption of water
• Solutes are ingested
• magnesium
• sorbitol
• malabsorption of food (mucosal injury, lactase
  deficiency)

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Secretory diarrhea

• Excess secretion of electrolytes, fluid across
  mucosa
• Usually coupled with decrease in absorption
• Watery, high-volume diarrhea with dehydration
• Enterotoxins Cholera, E. coli, food poisoning,
  Rotavirus (?), Norwalk virus (?)

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Rotavirus Clinical Syndromes

• Asymptomatic carriers
• Diarrheal illness
• 2-3 day incubation period
• diarrhea, vomiting fever 3-7 days
• high infectivity

• Complications
• dehydration
• chronic diarrhea
• dissemination
• NEC

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Diagnosis of rotavirus

• Electron microscopy
• Small intestine
• Stool
• Antigen in stool
• commercial ELISA
• research PCR, nucleic acid probes

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Therapy for rotavirus

• Rehydration
• ORT
• Intravenous
• Probiotics
• lactobacilllus GG
• Bismuth

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Oral rehydration solutions
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Prevention of Rotavirus

• Natural immunity 93 protective (sIgA)
• Vaccination
• heterologous rotavirus (bovine, rhesus)
• reassortment rotavirus (rhesus-human)
• nonreplicating particles
• naked DNA

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Calicivirus

• Norwalk virus and Norwalk-like
• Sapporo-like viruses
• Vesivirus
• Lagovirus
• All single stranded RNA viruses

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Norwalk virus
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Norwalk virus

• winter vomiting disease 1968, Norwalk OH
• Cause 40 of nonbacterial epidemics
• Explosive epidemics
• camps, cruise ships, nursing homes
• Food borne illness
• raw shellfish

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Food-borne illness
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Shellfish-borne infections
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Norwalk virus Clinical Features

• 24-48 hour incubation period
• vomiting prominent
• diarrhea 1-3 days
• less severe than rotavirus
• affects all ages
• antibodies in 60 of adults
• complications rare
• immunocompromised

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How does Norwalk virus cause diarrhea?

• Infection affects proximal small bowel
• Patchy mucosal injury
• Malabsorption
• ? Excess secretion

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Norwalk virus
2 days
6 days
Before ingestion
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Diagnosis of Norwalk virus

• Clinical diagnosis (exclude rotavirus)
• Immune EM
• Serology of antibody response
• enzyme immunoassays
• RT-PCR
• oligonucleotide probes

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Treatment of Norwalk virus

• Rehydration
• Supportive measures
• bismuth
• antidiarrheals (Lomotil, Immodium)

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Other viruses causing gastroenteritis

• Astrovirus
• children, outbreaks
• Adenovirus
• children, prolonged course
• Torovirus
• children, bovine pathogen

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Cytomegalovirus

• Herpesvirus
• Immune competent
• Mononucleosis-type syndrome
• Immunocompromised
• retinitis
• hepatitis
• gastrointestinal involvement (colon)

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Cytomegalovirus colitis