To determine whether bronchitis is caused by a virus or a bacterium, it can generally be distinguished by clinical symptoms, total and classified white blood cell counts in routine blood tests, and sputum cultures. 1. Clinical symptoms. Generally, patients with bronchitis caused by viral infection cough, cough sputum, sputum is white, and systemic symptoms are more obvious, such as fatigue, myalgia, with or without fever, etc., while patients with bronchitis caused by bacterial infection may have yellow, purulent sputum, and chills and high fever may occur. 2. The total number of leukocytes and classification count in blood routine. Bronchitis caused by bacterial infection is usually accompanied by an increase in the total number of white blood cells and the percentage of neutrophils, while those caused by viral infection usually have a normal or slightly lower white blood cell count and neutrophils, and a higher lymphocyte count. 3. Sputum culture. If pathogenic bacteria are found in the sputum culture of bronchitis patients, it is clear that it is caused by bacterial infection; if virus is found in the culture, it suggests that it may be caused by viral infection. However, these ways of judgment can only have a certain reference value in most cases, not absolute, many cases are difficult to distinguish between bacteria and viruses, need to be actively treated under the guidance of the doctor.