Cough sometimes with yellow sputum indicates bacterial infection, common diseases include pneumonia, bronchitis, bronchiectasis. 1. Pneumonia, bronchitis: coughing up yellow sputum indicates the presence of purulent cells. Consider infectious diseases of the lungs, such as pneumonia, bronchitis, etc., which are mainly caused by infections of Streptococcus pneumoniae, Staphylococcus pneumoniae, Mycoplasma and Chlamydia and other pathogens. 2. Bronchial dilatation: the respiratory secretions of these patients will be retained, when the position is changed, the secretions will stimulate the bronchial tubes to cause coughing and coughing up sputum. In addition to the above diseases, lung abscess and cavitary tuberculosis can also cause the above symptoms. It is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy.