If a child has a fever and is breathing rapidly, it is not necessarily due to pneumonia. First of all, fever and fast breathing are caused by pneumonia. In this case, children have inflammation of the lungs, which can cause a violent cough and a persistent high fever with a significantly faster breathing rate. Because pneumonia is caused by inflammation of the alveoli, children with inflammation of the alveoli can cause a decrease in oxygen exchange capacity, which can cause hypoxemia, and the presence of hypoxemia in children can stimulate a significant increase in the number of breaths. Secondly, it is caused by common respiratory infections. If a child has a common respiratory infection, such as acute bronchitis or acute upper respiratory infection, it can also compensate for faster breathing during fever. In this case, the child’s cough is not very intense and there is no solid lung shadow on the chest X-ray.