A patient with gastroenteritis experiences a strong desire to vomit. It is just another way to get rid of the toxins and infection. Just like in case of diarrhea, a person starts losing valuable nutrients and large amounts of water when vomiting regularly; it is important to increase the number of consumed foods and water. The stomach flu is one more health condition, which is characterized by both of these symptoms at the same time. Once you consume a dodgy meal or contact with an ill individual, you may also experience strong nausea.