What is rotavirus? There is a virus that mainly affects infants and young children. It causes mild upper respiratory symptoms at first, then vomiting and acute diarrhea, often leading to dehydration. The virus is called “rotavirus” because it looks like a wheel under an electron microscope. Rotavirus can affect people of any age and often affects children under 6 years of age, with young children under 1 year of age being the most at risk. The younger the child, the more severe the symptoms. The symptoms are characterized by acute watery stools, which makes it particularly likely to cause dehydration. In the early stages of rotavirus diarrhea, fluids containing certain electrolytes, such as oral rehydration salts, should be supplemented; in the later stages, due to lactose intolerance, breast milk + lactase or lactose-free formula can be insisted upon. Probiotics are also useful to shorten the course of the disease. When a child has diarrhea, a stool specimen can be taken for direct rotavirus antigen testing, and the test is more accurate. Because rotavirus is divided into several types, it is theoretically possible to get rotavirus more than once, but in practice, few infants and children get it more than twice.