下呼吸道感染(lower respiratory tract infection,LRTI)是病毒、细菌、真菌或寄生虫等病原微生物感染侵入会厌以下的气管、支气管及肺部引起的炎症反应,是全球范围内常见的公共健康问题。目前,由于外来致病因子侵袭引起的肺部感染是导致人类死亡的第三大原因[1]。由于其高发病率、高病死率,给个人、家庭乃至整个社会都带来了沉重的经济负担。人体下呼吸道时刻暴露于各种病原微生物、环境毒 Lower respiratory tract infection (LRTI) is a common global public health problem caused by the invasion of pathogenic microorganisms, such as viruses, bacteria, fungi or parasites, into the trachea, bronchi and lungs of the epiglottis. Currently, the third most common cause of death in humans is lung infection due to invasion of extra virions [1]. Due to its high morbidity and high mortality, it poses a heavy financial burden to individuals, families and society as a whole. Lower respiratory tract exposure to a variety of pathogenic microorganisms, environmental poisoning