My son's temp went to 39.8 earlier today and he was sick after i gave him liquid nurofen. he wasn't sick loads and it was mainly water. rotavirus or h?

Many possible causes: Children with fever often vomit a few times, especially after taking medication, and does not necessarily indicate a gastroenteritis infection like rotavirus. Continue to offer fluids regularly in spite of vomiting, as more fluid is often retained than is lost, and it will help to prevent dehydration. It is safe to give a repeat dose if vomiting was immediate. See your doctor if fever persists.