In a normal blood routine test, the white blood cell count is 4 - 10 × 10⁹ per liter. If the white blood cell count is higher than 10 × 10⁹ per liter, it is called leukocytosis. Many factors may lead to an increase in white blood cell count. ## Firstly, physiological factors may cause leukocytosis. For example, after intense exercise, emotional stress, or a full meal, the white blood cell count may increase. This is mainly because when stimulated by these factors, the body's secretion of catecholamines increases, causing the white blood cells in the marginal pool to enter the circulating pool. In this case, the increase in white blood cell count is temporary. ## Secondly, pathological leukocytosis. The most common cause is infection, especially bacterial infection. If an infant has a high white blood cell count, an infection factor cannot be ruled out. A systematic examination can be carried out at the hospital. Bacterial culture and drug - sensitivity tests can be performed. Based on the results of the drug - sensitivity tests, sensitive antibiotics can be selected for anti - infection treatment. At the same time, peripheral blood smear and bone marrow aspiration examinations can also be carried out to make a clear diagnosis and rule out other causes of the high white blood cell count in the infant.