Gastroenteritis
Acute gastroenteritis is inflammation of the stomach and intestines causing diarrhea and often vomiting, most commonly from norovirus, and is typically self-limited.
Symptoms
Watery diarrhea, vomiting, abdominal cramping, and sometimes low-grade fever, usually lasting a few days.
Causes and risk
Norovirus predominates among viral causes; bacterial and foodborne causes are less common but more likely to need targeted testing or treatment. Close contact (households, schools, cruise ships) drives outbreaks.
How it is evaluated
Most cases don't need testing. When it's indicated, molecular/PCR panels are preferred; testing and treatment decisions follow IDSA 2017 and ACG 2016 guidance on when a higher-risk feature is present.
Treatment
Oral rehydration is the mainstay of treatment for nearly everyone. Antibiotics are actively harmful in some situations -- Shiga toxin-producing E. coli and uncomplicated bloody diarrhea specifically -- so they are not given by default. Loperamide should be avoided when diarrhea is bloody or clearly inflammatory.
When to seek care
Signs of dehydration (dizziness, dry mouth, reduced urination), inability to keep fluids down, high fever, or bloody stools need prompt evaluation.