Stomach Flu (Viral Gastroenteritis): Causes, Transmission, Prevention, and Care

Viral gastroenteritis ("stomach flu") is acute inflammation of stomach/intestines from viruses — not influenza. Highly contagious; all ages affected.

Major Pathogens

• Norovirus: #1 cause (all ages); explosive vomiting, diarrhea; 12–48 hr incubation; 1–3 days illness.
• Rotavirus: #1 in young children (pre-vaccine); severe dehydrating diarrhea; vaccine since 2006 ↓ hospitalizations 80%.
• Adenovirus (types 40/41): Prolonged diarrhea (up to 2 wks).
• Astrovirus, Sapovirus: Milder, similar.

Transmission

• Fecal-oral: contaminated hands, surfaces, food, water.
• Aerosolized vomitus (norovirus).
• Person-to-person (household, daycare, cruise ships, nursing homes).

Symptoms

• Watery diarrhea, nausea, vomiting, abdominal cramps.
• Low-grade fever, myalgia, headache.
• Dehydration signs: dry mouth, ↓ urine, lethargy, sunken eyes/fontanelle.

Prevention

• Handwashing: Soap + water 20 sec (alcohol gel < effective vs. norovirus).
• Surface Disinfection: Bleach (1000–5000 ppm) for norovirus.
• Food Safety: Cook shellfish thoroughly; exclude ill food handlers.
• Rotavirus Vaccine: 2- or 3-dose series (infancy).
• Isolation: Stay home 48 hrs after last symptom.

Management

• Oral Rehydration Solution (ORS): WHO formula / Pedialyte — small frequent sips.
• Continue Feeding: Breastmilk, formula, age-appropriate diet. BRAT not recommended.
• Antiemetics (ondansetron): May facilitate ORS tolerance in children.
• Antidiarrheals: Avoid in children; loperamide only adults, not bloody/febrile.
• Antibiotics: Never for viral. Only if bacterial proven (culture).

Red Flags for Medical Care

• Signs of moderate/severe dehydration.
• High fever (>102°F / 39°C), bloody stool, severe pain.
• Symptoms >7 days (adults) or >3 days (children).
• Immunocompromised, pregnant, elderly.

Most recover fully with hydration. Norovirus immunity short-lived → reinfection common.