What are the typical clinical manifestations of acute viral gastroenteritis, including age‑related differences and red‑flag signs that require urgent evaluation?

Symptoms of Acute Viral Gastroenteritis

Acute viral gastroenteritis presents with acute onset of nausea, vomiting, non-bloody diarrhea, and abdominal cramps, with symptom patterns varying by age and viral pathogen. 1

Core Clinical Features

The hallmark symptoms across all age groups include:

• Nausea (79% of cases) 1
• Abdominal cramps (71% of cases) 1
• Vomiting (69% of cases) 1
• Non-bloody diarrhea (66% of cases) - the absence of blood is a critical distinguishing feature 1
• Headache (50% of cases) 1
• Low-grade fever (37% of cases) 1
• Chills (32% of cases) 1
• Myalgias (26% of cases) 1

Age-Related Symptom Differences

Children and Infants

Vomiting is the predominant feature in children, occurring in 80-90% of cases and often preceding diarrhea. 2

• Rotavirus (most common in ages 3-24 months): Acute onset of fever and vomiting followed 24-48 hours later by watery diarrhea 2
• Vomiting typically lasts only 24 hours or less despite overall illness duration of 3-8 days 3
• Children may have 10-20 bowel movements per day during acute illness 3
• Upper respiratory symptoms frequently accompany gastrointestinal symptoms 4
• Ketonuria commonly develops from metabolic stress and dehydration 2

Adults and Older Children

Diarrhea is relatively more prevalent than vomiting in adults, while children experience proportionally more vomiting. 1

• Norovirus (most common in school-age and older): Prominent nausea with vomiting, non-bloody diarrhea, and abdominal cramps 1
• Constitutional symptoms (headache, fever, chills, myalgias) occur in 25-50% of cases 1

Elderly Patients

The elderly experience more severe symptoms, prolonged illness duration (4-6 days versus 1-3 days), and persistence of constitutional symptoms for several weeks after gastrointestinal symptoms resolve. 1, 5

• Higher risk of complications including death from electrolyte imbalance 1
• More likely to require hospitalization and intravenous fluid therapy 1

Timing and Duration

Incubation Period

• Norovirus: 12-48 hours (most common) 1
• Rotavirus: 1-3 days 3
• Astrovirus: 24-36 hours 1, 5
• Calicivirus: 1-3 days 5

Illness Duration

• Norovirus: 12-60 hours (mean 2-3 days) in healthy adults; 4-6 days in children, elderly, and hospitalized patients 1, 5
• Rotavirus: 3-8 days 5, 2, 4
• Astrovirus: 1-4 days 1, 5
• Calicivirus: Average 4 days 5

Red-Flag Signs Requiring Urgent Evaluation

Bloody diarrhea immediately excludes typical viral gastroenteritis and mandates evaluation for bacterial or other serious etiologies. 1

Immediate Medical Attention Required:

• Bloody stools - suggests bacterial infection, intussusception, or other serious pathology 5, 2
• Bilious vomiting - indicates possible malrotation with volvulus or intestinal obstruction 2
• Signs of severe dehydration: 5, 3
  • Altered mental status
  • Poor skin turgor
  • Dry mucous membranes
  • Decreased urine output
  • Prolonged capillary refill time
• Severe or persistent abdominal pain - may indicate complications 5
• High fever (not low-grade) - suggests bacterial co-infection 5

Consider Medical Evaluation If:

• Symptoms persist beyond expected duration (>3-7 days) 5
• Immunocompromised status (chronic viral shedding and severe illness possible) 1, 3
• Elderly patient (lower threshold for evaluation due to complication risk) 5
• Persistent fever suggesting bacterial co-infection 5

Common Pitfalls to Avoid

Do not assume all acute gastroenteritis is viral - the presence of blood, prolonged high fever, or severe abdominal pain requires investigation for bacterial, parasitic, or surgical causes. 1, 5

• Viral gastroenteritis never causes bloody diarrhea 1
• Symptoms persisting beyond 7 days warrant stool testing for bacterial pathogens and parasites 5
• Recent antibiotic use (within 8-12 weeks) raises concern for Clostridioides difficile infection 5
• Immunocompromised patients may experience chronic norovirus infection requiring earlier evaluation 1, 3
• The elderly require aggressive hydration monitoring, especially if on diuretics 3