Norovirus (Stomach Bug)

Norovirus, often called the "stomach bug" or "stomach flu," is a highly contagious virus that causes sudden onset of vomiting and diarrhea. Despite being called "stomach flu," it's not related to influenza (the flu). **Key Facts:** - **Highly contagious:** Can spread from just 18 viral particles - **Rapid onset:** Symptoms start 12-48 hours after exposure - **Short duration:** Usually resolves in 1-3 days - **No treatment:** No antivirals; supportive care only - **Prevention:** Hand washing is critical (hand sanitizer less effective) **How It Spreads:** - Direct contact with infected person - Contaminated food or water - Touching contaminated surfaces then touching mouth - Airborne particles from vomiting **Related Conditions:** - [Food poisoning](/condition/food-poisoning) — bacterial cause, similar symptoms - [Stomach flu](/condition/stomach-flu) — general term for viral gastroenteritis - [Diarrhea](/condition/diarrhea) — main symptom of norovirus - Often confused with [food poisoning](/condition/food-poisoning) — see our [norovirus vs food poisoning comparison](/compare/norovirus-vs-food-poisoning) **Important:** Dehydration is the main concern, especially in children and elderly.

**How Norovirus Infects You:** **1. Viral Entry:** Norovirus enters through your mouth when you eat contaminated food, drink contaminated water, or touch your mouth after touching contaminated surfaces. **2. Intestinal Infection:** The virus attacks the lining of your small intestine, causing inflammation. This disrupts normal fluid absorption and triggers the vomiting and diarrhea response. **3. Rapid Multiplication:** Norovirus replicates extremely quickly in the gut, which is why symptoms appear suddenly and intensely. **Why It's So Contagious:** - Only 18-1,000 viral particles needed to cause infection - Infected people shed billions of viral particles - Virus survives on surfaces for days to weeks - Resistant to many common disinfectants - Hand sanitizer is less effective than soap and water **Peak Season:** Norovirus is most common from November through April, when: - People spend more time indoors - Holiday gatherings increase transmission - Cold weather helps virus survive longer on surfaces **High-Risk Settings:** - Cruise ships (close quarters, shared dining) - Nursing homes and hospitals - Schools and daycares - Restaurants and catered events

**No Specific Treatment:** There are no antiviral medications for norovirus. Treatment focuses on preventing dehydration and managing symptoms. **Hydration (Most Important):** - Oral rehydration solutions (Pedialyte) for mild-moderate dehydration - IV fluids for severe dehydration (hospital) - Small, frequent sips rather than large amounts - Continue breastfeeding infants **Symptom Management:** - Anti-nausea medications (ondansetron) for severe vomiting - Avoid anti-diarrheal medications unless necessary (delays virus clearance) - Acetaminophen for fever and body aches **Diet Progression:** 1. Clear liquids only while actively vomiting 2. BRAT diet as symptoms improve 3. Gradually reintroduce normal foods 4. Avoid dairy, fatty foods, caffeine for 24-48 hours after recovery **When Hospitalization Needed:** - Severe dehydration (unable to keep fluids down) - Bloody stool or vomit - High fever - Symptoms lasting more than 3 days - Very young children, elderly, or immunocompromised **Prevention:** - Wash hands thoroughly with soap and water for 20+ seconds - Disinfect surfaces with bleach-based cleaner - Wash contaminated laundry in hot water - Stay home 48 hours after symptoms resolve