The term "stomach bug" refers to a gastrointestinal illness caused by a virus or bacteria. It is often characterized by symptoms such as nausea, vomiting, diarrhea, and abdominal pain. The stomach bug can be highly contagious and spread easily through contact with an infected person or consuming contaminated food or water. While most cases are mild and resolve on their own within a few days, severe dehydration can occur in some instances, particularly among young children, the elderly, and those with compromised immune systems.