Diarrhea, Viral Evaluation

Diagnosis

Indications for Testing

• Diarrhea ≥3 days; prolonged diarrhea with history of travel
  • Most cases of norovirus and rotavirus are diagnosed clinically

Laboratory Testing

• Guide to confirming diagnosis in foodborne disease (CDC)
• CBC – may help eliminate bacteria as etiology if leukocytosis is not present
• Stool culture – preferred test to rule out suspected diarrhea (most useful if diarrhea lasts ≥3 days or is bloody)
• Norovirus 
  • Reverse transcription polymerase chain reaction (RT-PCR) detection for genogroups I and II – most sensitive/specific test for norovirus
  • EIA (antigen detection) – not as sensitive as PCR
  • Electron microscopy – insensitive and lab specific
• Rotavirus
  • EIA
  • Latex agglutination
• Ova and parasite exam
  • Does not aid in diagnosis of viral diarrhea
  • Consider ova and parasite exam and Giardia EIA and/or Clostridium difficile testing if patient has defined risk factors

Differential Diagnosis

• Bacterial or parasitic diarrhea
• Primary or metastatic cancer
• Malabsorption
• VIPoma
• Inflammatory bowel disease
• Irritable bowel syndrome
• Celiac disease

Clinical Background

Etiology of diarrhea may be infectious or noninfectious presenting with acute (<7 days) or chronic (>7 days) symptoms. Viral agents are the most common cause of diarrheal illness. Norovirus (Norwalk-like virus) and rotavirus are the two predominant viral agents. Parasites are an infrequent or rare cause of acute diarrhea but a more common cause of chronic diarrhea.

• Acute diarrhea (acute gastroenteritis) – duration 1-7 days
  • Frequently infectious
  • May be foodborne, waterborne, or outbreak associated
  • Most commonly caused by viruses and occasionally bacteria
  • Testing for gastrointestinal parasites generally not recommended for acute diarrheal episodes
• Chronic diarrhea – duration >7 days, often longer
  • More commonly noninfectious
  • Testing for parasites should be considered
• Predominant viral agents
  • Norovirus

    Epidemiology Leading cause of nonbacterial gastroenteritis worldwide In the U.S., norovirus causes millions of infections annually, with outbreaks commonly occurring in all age groups and in varied environments such as the following Cruise ships Restaurants – salad bars Schools Healthcare facilities  Transmission occurs mainly through the fecal-oral route by ingestion of contaminated food (eg, shellfish) or water, but can be airborne (in vomitus) Norovirus has a characteristically low infectious dose and can survive relatively high levels of disinfectants and varying temperatures, all of which facilitate its transmission Organism Norovirus, formerly known as Norwalk-like virus, is a member of the Caliciviridae family Single-stranded RNA virus Genogroups I and II account for ~99% of norovirus infections in humans Clinical Presentation Usually mild or self-limiting disease with high transmission rates – often ≥30% among contacts of infected patients Most common symptoms – acute onset diarrhea and vomiting with abdominal cramps, nausea, fever, headache Symptoms occur within 24-48 hours of infection, may continue for 12-60 hours Transplant patients often have chronic diarrhea Symptoms in small bowel transplant patients resemble allograft rejection Treatment Supportive care – infection is self-limited Prevention Hygiene/handwashing, disinfection of contaminated surfaces Infection control measures are important in limiting the spread in hospital settings

    Rotavirus

    Epidemiology Most important cause of severe dehydrating diarrhea in children <5 years Rotavirus type A is responsible for 25-60% of severe infantile diarrhea worldwide Transmission via fecal-oral route Universal infection – nearly all children have circulating antibodies by 2-3 years Organism Double-stranded RNA virus Seven antigenic groups Group A most common Clinical Presentation Varies from asymptomatic to severe dehydration and death Mild fever and emesis for 2-3 days Watery diarrhea for 3-5 days following fever Bloody diarrhea is rare Severe and prolonged disease may occur in patients with the following Significant malnutrition Immune deficiencies (eg, HIV) Other disease such as diabetes mellitus, congenital heart disease, or pulmonary disease May involve extra-intestinal sites – central nervous system, liver, spleen, or kidney, especially in immunocompromised children Treatment Supportive care Prevention Handwashing and vaccination

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory

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Test Name and Number	Comments
Rotavirus and Adenovirus 40-41 Antigens 0065067 Method: Qualitative Enzyme Immunoassay	Diagnose rotavirus- and adenovirus-associated gastroenteritis

Diagnostic Algorithm

  Diarrhea, Acute Testing Algorithm