one third of the world population is believed to be infected with TB. Fortunately, only

據信世界上大約有三分之一的人口是肺結核病患

about 5% of these infections progress to active disease. The other 95% of infected people

幸運的是,僅5%的肺結核會發展成開放性肺結核

are said to have a dormant or latent infection; they do not develop any symptoms, and do not

剩下95%的病患則是非開放性肺結核,不會有症狀出現,不會傳染

transmit the disease. Tuberculosis is caused by a rod-shaped bacterium,

肺結核是由桿狀的細菌所造成

or a bacillus, called Mycobacterium tuberculosis. An infection is initiated following inhalation

這種桿菌名叫「結核分枝桿菌」(Mycobacterium tuberculosis)

of mycobacteria present in aerosol droplets discharged into the atmosphere by a person

開放性肺結核病患的飛沫可在空氣中停留數小時

with an active infection. The transmission process is very efficient as these droplets

吸入含有結核菌的飛沫便會引起感染

can persist in the atmosphere for several hours and the infectious dose is very low

肺結核的傳染性高,吸入一點就會引起感染

– less than 10 bacilli are needed to start the infection.

少於十個結核菌就能引發感染

Once in the lung, the bacteria meet with the body’s first-line defense - the alveolar

結核菌進入肺部後會遇見身體的第一道防線：肺泡巨噬細胞

macrophages. The bacteria are ingested by the macrophages but manage to survive inside.

肺泡巨噬細胞會吞噬結核菌,而結核菌能繼續存活在裡頭

Internalization of the bacilli triggers an inflammatory response that brings other defensive

結核菌在巨噬細胞裡面會引起發炎反應,引來其他免疫細胞來到附近

cells to the area. Together, these cells form a mass of tissue, called a granuloma, characteristic

這些細胞會在巨噬細胞外圍形成肉芽腫組織,這是肺結核的特色

of the disease. In its early stage, the granuloma has a core

初期,肉芽腫的中心是受到感染的巨噬細胞

of infected macrophages enclosed by other cells of the immune system. As cellular immunity

巨噬細胞由免疫細胞包圍

develops, macrophages loaded with bacteria are killed, resulting in the formation of

免疫細胞作用之後,裡頭充滿結核菌的巨噬細胞會被殺死,造成肉芽腫中心壞死

the caseous center of the granuloma. The bacteria become dormant but may remain alive for decades.

使肺結核進入潛伏期,但結核菌仍然能存活數十年

This enclosed infection is referred to as latent tuberculosis and may persist throughout

這種包圍結核菌的感染為非開放性肺結核,病患可能一生都不會發病

a person's life without causing any symptoms. The strength of the body’s immune response

人體的免疫系統反應決定感染是否終止

determines whether an infection is arrested here or progresses to the next stage. In healthy

或者進入下一個階段

people, the infection may be stopped permanently at this point. The granulomas subsequently

健康的人感染在這個階段就停止,肉芽腫接著癒合, 留下微小的鈣化傷口

heal, leaving small calcified lesions. On the other hand, if the immune system is compromised

另一方面,如果免疫系統被其他免疫抑制藥影響

by immunosuppressive drugs, HIV infections, malnutrition, aging, or other factors, the

或是病患得到愛滋病、營養不良、老年或其他原因

bacteria can be re-activated, replicate, escape from the granuloma and spread to other parts

細菌就會活化,複製增生,逃出肉芽腫

of the lungs causing active pulmonary tuberculosis. This reactivation may occur months or even

並散播到肺部其他地方造成開放性肺結核,初期感染後又復發

years after the initial infection. In some cases, the bacteria may also spread

可能是數個月或者數年之後,有些案例中,細菌會透過淋巴系統或血液

to other organs of the body via the lymphatic system or the bloodstream. This widespread

散播到其他器官

form of TB disease, called disseminated TB or miliary TB, occurs most commonly in the

這種常見的肺結核類型叫做散播性結核或粟粒性結核

very young, the very old and those with HIV infections.

最常發生在小朋友、老年人和愛滋病病患的人身上

Tuberculosis is generally treatable with antibiotics. Several antibiotics are usually prescribed

抗生素通常能治癒肺結核,一些抗生素的療程通常要很多個月

for many months due to the slow growth rate of the bacteria. It’s very important that

因為細菌的增生速度慢

the patients complete the course of the treatment to prevent development of drug-resistant bacteria

重要的是,結核病病患要走完療程,避免細菌發展出抗藥性

and re-occurrence of the disease.

也避免疾病復發