Viral Gastroenteritis¶
Chapter 209 | Part 5: Infectious Diseases
KEY CLINICAL POINTS¶
- Viral gastroenteritis is caused by RNA viruses (rotavirus, norovirus, sapovirus, astrovirus) and DNA viruses (adenovirus types 40/41).
- Norovirus is the most common cause of acute gastroenteritis in adults and the leading cause of medically attended gastroenteritis in children in developed countries.
- Rotavirus is a major cause of severe dehydration and mortality in children <5 years in developing countries, with global mortality rates peaking in sub-Saharan Africa and southern Asia.
- Diagnosis relies on molecular assays (PCR), enzyme immunoassays (EIA), and electron microscopy (EM), with norovirus accounting for ~50% of outbreaks.
- Rotavirus vaccination has reduced hospitalizations by 70–80% in the U.S. and is recommended globally, with moderate efficacy (50–65%) in low-resource settings.
1. DEFINITION & OVERVIEW¶
Viral gastroenteritis is an acute intestinal infection characterized by vomiting, diarrhea, and abdominal cramps. It is caused by enteric viruses that replicate in the gastrointestinal tract and are transmitted via fecal-oral route, aerosolization, or contaminated surfaces. The illness is self-limiting in most cases but can lead to severe dehydration, particularly in young children and immunocompromised individuals.
Table 209-1: Viral Causes of Gastroenteritis among Humans¶
| Virus | Family | Genome | Primary Age Group at Risk | Clinical Severity | Detection Assays |
|---|---|---|---|---|---|
| Group A rotavirus | Reoviridae | Double-strand segmented RNA | Children <5 years | + + + | EIA (commercial), RT-PCR, EM, PAGE |
| Norovirus | Caliciviridae | Positive-sense single-strand RNA | All ages | + + | RT-PCR, EM, EIA (commercial) |
| Sapovirus | Caliciviridae | Positive-sense single-strand RNA | Children <5 years | + | RT-PCR, EM |
| Astrovirus | Astroviridae | Positive-sense single-strand RNA | Children <5 years | + | EIA, RT-PCR, EM |
| Adenovirus (types 40 and 41) | Adenoviridae | Double-strand DNA | Children <5 years | +/+ + | EIA (commercial), PCR, EM |
1.1 Viral Agents¶
Key pathogens include rotavirus (most common in children), norovirus (most common in adults), sapovirus (children), astrovirus (children), and adenovirus (types 40/41). Norovirus and rotavirus are the leading causes of outbreaks and hospitalizations.
1.2 Transmission¶
Predominantly fecal-oral route, but aerosolization and fomite transmission are also common. Norovirus outbreaks frequently occur in closed settings (e.g., cruise ships, schools).
2. EPIDEMIOLOGY¶
Acute infectious gastroenteritis is a leading cause of death among children in developing countries (0.5 million annual deaths). Rotavirus is most prevalent in children <5 years, with global mortality rates peaking in sub-Saharan Africa and southern Asia (Fig. 209-2). Norovirus outbreaks are common worldwide, with ~50% of reported outbreaks attributed to norovirus.
Table 209-2: Characteristics of Gastroenteritis Caused by Viral and Bacterial Agents¶
| Feature | Viral Gastroenteritis | Bacterial Gastroenteritis |
|---|---|---|
| Setting | Incidence similar in developing and developed countries | More common in settings with poor hygiene and sanitation |
| Seasonality | Winter seasonality in temperate climates; year-round in tropical areas | More common in summer/rainy months, especially in developing countries |
| Incubation Period | 1–3 days (shorter for norovirus) | 1–7 days (shorter for toxin-producing bacteria) |
| Fever | Common with rotavirus and norovirus | Common with inflammatory agents (Salmonella, Shigella) |
| Vomiting | Prominent in children; less common in adults | Common with preformed toxin-producing bacteria (Staphylococcus, Bacillus) |
| Diarrhea | Nonbloody in almost all cases | Occasionally bloody with inflammatory agents |
| Duration | 1–3 days for norovirus/sapovirus; 2–8 days for other viruses | 1–2 days for toxin-producing bacteria; 2–8 days for most others |
| Diagnosis | Diagnosis of exclusion; EIA/PCR for rotavirus/adenovirus | Stool culture on special media; molecular techniques for epidemiology |
2.1 Risk Factors¶
Young children, elderly, immunocompromised individuals, and those in crowded settings (e.g., daycare, cruise ships) are at highest risk. Poor sanitation and hygiene exacerbate transmission.
2.2 Seasonality¶
Rotavirus peaks in temperate climates during fall/winter; norovirus shows winter seasonality in temperate regions but year-round activity in tropical areas.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Viruses disrupt intestinal epithelial cells, leading to secretory diarrhea. Rotavirus targets mature enterocytes in the proximal small intestine, causing villous atrophy and crypt hyperplasia. Norovirus binds to histo-blood group antigens (HBGAs) on gastric epithelium, inducing transient lesions in the jejunum.
3.1 Rotavirus¶
Causes severe dehydration in children; genetic reassortment contributes to rapid evolution. VP7 (G-protein) and VP4 (P-protein) determine serotype and neutralizing antibodies. NSP4 protein acts as an enterotoxin.
3.2 Norovirus¶
Genetic predisposition to infection based on HBGA phenotypes. Broadly neutralizing antibodies (bNAbs) target conserved epitopes in the viral envelope. VLP-based vaccines show 47–61.8% efficacy in trials.
4. CLINICAL FEATURES¶
Acute onset with vomiting, diarrhea, abdominal cramps, and fever. Norovirus often presents with vomiting as the sole feature in children. Rotavirus causes nonbloody diarrhea with frequent watery stools. Severe dehydration is more common in infants and elderly.
4.1 Symptomatology¶
Nausea, vomiting, abdominal cramps, diarrhea (nonbloody), fever, and malaise. Vomiting is more prevalent in children; diarrhea dominates in adults.
4.2 Complications¶
Severe dehydration, electrolyte imbalances, and secondary infections. Rotavirus may cause intussusception in immunocompromised patients.
5. DIFFERENTIAL DIAGNOSIS¶
Distinguish from bacterial causes (e.g., Salmonella, Shigella) using stool exams (leukocytes, blood), PCR, and clinical presentation. Norovirus outbreaks should be differentiated from other viral agents using molecular testing.
5.1 Viral vs Bacterial¶
Viral: Nonbloody diarrhea, short duration, no fever. Bacterial: Bloody diarrhea, fever, leukocytes in stool, longer duration.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis is primarily by exclusion. Commercial EIA/PCR detects rotavirus, adenovirus, and norovirus. EM identifies viral particles. Stool cultures and molecular assays confirm bacterial causes.
6.1 Diagnostic Tests¶
RT-PCR for viral RNA, EIA for antigen detection, stool microscopy for leukocytes/blood, and culture for bacterial pathogens.
7. MANAGEMENT & TREATMENT¶
Supportive care with oral rehydration therapy (ORS) is critical. IV fluids for severe dehydration. Avoid antibiotics and antidiarrheals. Probiotics and immunoglobulins may reduce severity in high-risk patients.
7.1 Hydration¶
ORS is first-line for most patients. IV fluids required for severe dehydration or vomiting intolerance.
7.2 Antiviral Therapy¶
No specific antivirals available. VLP-based vaccines show promise for norovirus and rotavirus prevention.
8. PROGNOSIS & COMPLICATIONS¶
Most cases resolve within 1–3 days. Severe dehydration and electrolyte imbalances are the main complications. Rotavirus is a leading cause of diarrheal mortality in children <5 years in developing countries.
8.1 Mortality¶
Rotavirus mortality peaks in sub-Saharan Africa and southern Asia (Fig. 209-2). Norovirus rarely causes death but can lead to severe dehydration in vulnerable populations.
9. SPECIAL CONSIDERATIONS¶
Rotavirus vaccination (RotaTeq, Rotarix) has reduced hospitalizations by 70–80% in the U.S. and is recommended globally. Norovirus vaccines (VLP-based) are under development. Herd immunity from vaccination reduces community transmission.
9.1 Vaccination¶
Rotavirus vaccines (GI.1/GII.4 VLPs) show 47–61.8% efficacy. Norovirus vaccines are in clinical trials. Vaccination programs in low-income countries have reduced mortality.
9.2 Immunosuppressed Patients¶
Immunocompromised individuals may experience prolonged viral shedding and severe disease. Prophylactic immunoglobulins may be considered.
10. KEY POINTS & CLINICAL PEARLS¶
- Norovirus is the most common cause of acute gastroenteritis in adults and the leading cause of outbreaks.
- Rotavirus vaccination has reduced severe disease by 70–80% in the U.S. and is recommended globally.
- Norovirus outbreaks are diagnosed via RT-PCR and EIA, with ~50% of outbreaks attributed to norovirus.
- Severe dehydration is the primary complication; ORS is critical for management.
- VLP-based vaccines show promise for both norovirus and rotavirus prevention.