Norovirus, often responsible for the stomach flu, is a leading cause of viral gastroenteritis. It is highly contagious and primarily spreads through the fecal-oral route, including contaminated food, water, and surfaces. The virus affects the small intestine by damaging the villi and microvilli, leading to malabsorption of nutrients like fats and sugars. Symptoms typically appear 12 to 48 hours after exposure and include vomiting, diarrhea, abdominal pain, and fever, lasting 48 to 72 hours. Diagnosis is confirmed through RT-PCR testing of stool samples. Treatment focuses on supportive care, such as rehydration and antiemetics, as there is no vaccine available. Preventative measures include proper sanitation, handwashing, and avoiding contact with infected individuals.