Norovirus spreads easily through contaminated food, surfaces, or hands. FoodSafety.gov notes ready-to-eat foods touched by an infected food worker as a common source.
Symptoms usually start within 12 to 48 hours and include diarrhea, vomiting, nausea, and stomach pain. Illness typically lasts one to three days.
Wash hands with soap and water, stay home when sick, and clean contaminated surfaces.