Diarrhea, Viral Evaluation

Diagnostic Algorithm

  Diarrhea, Acute Testing Algorithm

Clinical Background

Acute gastroenteritis is one of the most common diseases in humans. Viral agents are an important cause of diarrheal illness. The two most common viral agents are:

• Norovirus (Norwalk-like virus)
• Rotavirus

Norovirus

Epidemiology

• Leading cause of nonbacterial gastroenteritis worldwide; genogroups I and II account for approximately 99% of Norovirus infections in humans
• In the U.S., Norovirus causes millions of infections annually, with outbreaks commonly occurring in all age groups and in varied environments such as:
  • Cruise ships
  • Restaurants (salad bars)
  • Schools
  • Healthcare facilities 
• Norovirus has a characteristically low infectious dose and can survive relatively high levels of disinfectants and varying temperatures, all of which facilitate its transmission
  • Transmission occurs mainly through the fecal-oral route by ingestion of contaminated food (eg, shellfish) or water, but can be airborne (in vomitus)

Organism

• Norovirus, formerly known as Norwalk-like virus, is a member of the Caliciviridae family
• Single-stranded RNA virus

Clinical Presentation

• Usually mild or self-limiting disease but shows high transmission rates (often ≥30%) among contacts of infected patients
• Most common symptoms – acute onset diarrhea and vomiting with abdominal cramps, nausea, fever and headache
• Symptoms occur within 24-48 hours of infection and can range from 12-60 hours in duration
• A cause of chronic diarrhea in transplant patients
  • Symptoms in small bowel transplant patients resemble allograft rejection

Treatment

• Supportive care, as infection is self-limited
• Infection control measures are important in limiting the spread in hospital settings

Prevention

• Hygiene/handwashing, disinfection of contaminated surfaces

Rotavirus

Epidemiology

• Most important cause of severe dehydrating diarrhea in children ages 5 and younger
• Rotavirus Type A is responsible for 25-60% of severe infantile diarrhea worldwide
• Transmission is via fecal-oral route
• Nearly all children have circulating antibodies by ages 2-3 (universal infection)

Organism

• Double-stranded RNA virus

Clinical Presentation

• Varies from asymptomatic to severe dehydration and death
• Mild fever and emesis for 2-3 days
• 3-5 days of watery diarrhea following fever
• Severe and prolonged disease may occur in patients with:
  • Significant malnutrition
  • Immune deficiencies
  • Other disease such as diabetes mellitus, congenital heart disease or pulmonary disease
  • May involve extra-intestinal sites (central nervous system, liver, spleen, kidney), especially in immunocompromised children

Treatment

• Supportive care

Prevention

• Handwashing and vaccination

Diagnosis

Norovirus

• Indications for testing – diarrhea >3 days, prolonged diarrhea with history of travel
• Laboratory testing
  • Most cases of Norovirus and Rotavirus are diagnosed on clinical presentation
  • CBC – may help eliminate bacteria as etiology in diarrhea if leukocytosis is not present
  • Stool
    • Reverse transcription polymerase chain reaction (RT-PCR) detection for genogroups I and II – preferred test for Norovirus
    • RT/PCR most sensitive
    • EIA (antigen detection) – not as sensitive as PCR
    • Electron microscopy – insensitive test and lab specific

Differential Diagnosis

• Bacterial or parasitic diarrhea
• Primary or metastatic cancer
• Malabsorption
• VIPoma

Pharmacogenetics and Therapeutic Drug Monitoring

Screening

Monitoring

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

Guidelines

General References

References from the ARUP Institute for Clinical and Experimental Pathology®