Most of the cough and sputum are caused by infectious diseases of the respiratory tract, bronchitis and pneumonia are easy to cause. If the sputum is yellow, it is mainly considered to be caused by bacterial infections, accompanied by cough, fever, also affects the appetite, generalized weakness, muscle aches and pains and other symptoms, need to be actively treated with antibacterial drugs and drugs to relieve cough and resolve sputum. If the sputum turns from yellow to white at this time, and the amount gradually decreases, it means that the symptoms have improved. However, if the systemic symptoms such as coughing and sputum do not decrease, and only the color of sputum turns white, it does not mean that there is an improvement, and it is also necessary to go to the hospital to do a checkup, usually needing to do a blood test, and needing to take a chest X-ray. According to the results of the examination and other clinical manifestations, to make a correct diagnosis and then active treatment, may be due to viral infections, or mycoplasma infections and other conditions caused.