Virus infection (35%):
70% to 80% of upper respiratory tract infections are caused by the virus. Including rhinoviruses, coronaviruses, adenoviruses, influenza and parainfluenza viruses, respiratory syncytial virus, echovirus, coxsackievirus and the like. Another 20% to 30% of the sense of bacteria caused by. Bacterial infection can be directly infected or secondary to the virus infection, the most common hemolytic streptococcus, followed by Haemophilus influenzae, pneumococcus, staphylococcus, etc., or even gram-negative bacteria.
External factors (30%):
Various causes of systemic or respiratory local defense decreased, such as cold, rain, climate change, fatigue, etc. can exist in the upper respiratory tract or from the outside invasion of the virus or bacteria quickly reproduce, and thus induce the disease. Frail, immunocompromised or susceptible to patients with chronic respiratory diseases.