Atypical pneumonia is mainly caused by viruses such as influenza and adenovirus, bacteria such as chlamydia and mycoplasma, and other unknown agents.

• 严重急性呼吸系统综合症主要是由流感病毒和腺病毒、菌如支原体和衣原体以及其他未明的微生物所引起的肺炎。