Infection has several characteristics. If the patient has fever symptoms, it is a virus infection, and the fever caused by virus infection is contagious. If it is mycoplasma or chlamydia infection, it is contagious. If it is acute bacterial bronchitis, it is generally not contagious. For example, a patient with acute bronchitis, fever, normal white blood cells, C-reactive protein and other inflammatory indicators are normal, suggesting that it is probably viral bronchitis, and this patient is contagious during fever. If the patient's white blood cells, C-reactive protein and inflammatory indicators are significantly increased, it may be related to bacterial infection, and the possibility of infection is significantly reduced. It should be remembered that mycoplasma infection may cause leukocytosis. This kind of patients have certain characteristics, usually accompanied by dry cough, fever, and epidemiological infection and contact history. Such patients are contagious.