什么是肺炎

肺组织因感染、吸入异物或受照射而产生的炎症和病变，但最常见者为由细菌所引起。肺炎枝原体（Streptococcus pneumoniae）是健康人体内最常见的致病原因。支气管和肺泡有可能发炎。咳嗽成为主要症状，痰中可带血斑。本病症状严重，但致死率低。肺炎链球菌（Streptococcus pneumoniae）较常见，一般来说病情也较严重，但通常只影响抵抗力较弱者，尤其是医院内的病人。肺炎克雷伯斯菌（Klebsiella pneumoniae）引起的肺炎，几乎只在免疫力低下的住院病患中发生，致死率很高。其他细菌性肺炎包括卡氏肺囊虫（Pneumocystis carinii）性肺炎（少见，爱滋病患除外）和退伍军人病。许多种类的肺炎可以抗生素治疗。病毒藉削弱个体的免疫系统提供细菌性肺炎病原体滋生的环境，而非直接导致肺炎。真菌性肺炎通常发生於抵抗力低的住院病人身上，但经由受污染的尘埃也可感染健康的人。发病快速并可能致死。胸内组织经X射线治疗（参阅radiation therapy）後可导致暂时性肺炎。

pneumonia

Inflammation and solidification of lung tissue caused by infection, foreign particle inhalation, or irradiation, but usually by bacteria. Mycoplasma pneumoniae is the most common cause in healthy individuals. The bronchi and alveoli may be inflamed. Coughing becomes severe and may bring up flecks of blood. It can be serious but is rarely fatal. Streptococcus pneumoniae is more common and generally more severe but usually affects only those with low resistance, especially in hospitals. A highly lethal form caused by Klebsiella pneumoniae is almost always confined to hospitalized patients with low immunity. Other bacterial pneumonias include Pneumocystis carinii pneumonia (rare except in AIDS) and Legionnaires' disease. Most respond to antibiotic treatment. Viruses set the stage for bacterial pneumonia by weakening the individual's immune system more often than they cause pneumonia directly. Fungal pneumonia usually occurs in hospitalized persons with low resistance, but contaminated dusts can cause it in healthy individuals. It can develop rapidly and may be fatal. X-ray treatment (see radiation therapy) of structures in the chest may cause temporary lung inflammation.