Tuberculosis is transmitted through the air.

Written by Wang Xiang Yu
Pulmonology
Updated on April 20, 2025
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The transmission of tuberculosis primarily depends on understanding its causative agent, which is the tubercle bacillus, also known simply as the tuberculosis bacillus. The main source of infection in tuberculosis is from patients who test positive for tuberculosis bacillus in their sputum. The respiratory tract is the principal route of transmission for tuberculosis patients. When patients who test positive for bacillus in their sputum cough, expel sputum, sneeze, or even speak loudly, they generate a large amount of droplets containing the tuberculosis bacillus. These bacteria can remain suspended in the air for a relatively long time. In poorly ventilated indoor environments, they may stay airborne for up to five hours. Healthy individuals can contract respiratory infections upon inhaling these bacteria. Furthermore, a very small portion of patients are infected through consuming milk or other dairy products from cows with tuberculosis.

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Written by Han Shun Li
Pulmonology
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How is tuberculosis treated?

The treatment of tuberculosis generally involves two aspects: etiological treatment and symptomatic management. Etiological treatment targets the tuberculosis bacteria with medication. Modern anti-tuberculosis chemotherapy regimens are quite mature, employing strategies such as early and combined use, appropriate dosing, regular administration, and full-course treatment, which result in a very high cure rate. Additionally, there is symptomatic management, for example, cough suppressants for patients with a cough, expectorants for those with excessive sputum, antipyretics if there is fever depending on the situation, and hemostatic drugs for patients coughing up blood, among others. The treatment of pulmonary tuberculosis is comprehensive and must be conducted under the guidance of a physician. It is crucial not to interrupt treatment casually to avoid affecting the effectiveness of the therapy, increasing the recurrence rate, and the emergence of drug resistance.

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Written by Hu Xue Jun
Pulmonology
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Symptoms of pulmonary tuberculosis

Now let me talk about the symptoms of tuberculosis. Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis, which can invade many organs, with pulmonary tuberculosis being the most common. The main symptoms are respiratory symptoms and systemic symptoms. The respiratory symptoms are mainly manifested as coughing, expectoration for more than two weeks, or blood in the sputum, which are common suspicious symptoms of pulmonary tuberculosis. Generally, the cough is mild, either dry or with a small amount of mucus. When cavities form, the amount of sputum may increase, and if there is a secondary bacterial infection, the sputum may become purulent. If there is concomitant bronchial tuberculosis, it will manifest as an irritating cough. About one-third of patients will experience hemoptysis, and some may experience massive hemoptysis. If the tuberculosis lesions involve the pleura, it can manifest as chest pain. Dyspnea is more common in patients with caseous pneumonia or those with a large amount of pleural effusion. These are local symptoms. Systemic symptoms mainly manifest as fever, which is the most common manifestation, often as long-term afternoon fever, meaning it begins to rise in the afternoon or evening, drops in the morning, and then returns to normal. Some patients may also experience fatigue, night sweats, loss of appetite, weight loss, etc. Women of childbearing age may experience menstrual disorders, etc.

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Written by Wang Xiang Yu
Pulmonology
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How is tuberculosis transmitted?

How is pulmonary tuberculosis transmitted? First, we need to know the pathogen of pulmonary tuberculosis, which is the tuberculosis bacillus. Tuberculosis bacillus is a type of bacterium that can live in our surrounding environment. Pulmonary tuberculosis also needs a source of infection, that is, a patient carrying the tuberculosis bacillus. The most common source of tuberculosis infection is usually patients with secondary pulmonary tuberculosis. Then, its mode of transmission mainly includes coughing, sneezing, laughing, and talking loudly, which can release the tuberculosis bacilli from the patient into the air, spreading them through droplets. Droplet transmission is the most important route for the spread of pulmonary tuberculosis. Additionally, pulmonary tuberculosis can also be transmitted through other routes such as the gastrointestinal tract or the skin, although these methods of transmission are less common.

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Written by Li Jiao Yan
Neonatology
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Does the BCG vaccine prevent tuberculosis?

The BCG vaccine primarily prevents infection by the tuberculosis bacillus, so it can prevent pulmonary tuberculosis. The protective effect of the BCG vaccine is mainly achieved through inducing a cell-mediated immune response. After vaccination, a primary infection is formed, which is processed by macrophages that transmit the antigen information to immune-active cells, leading to the differentiation and proliferation of T cells and the formation of sensitized lymphocytes. When the body is re-infected with the tuberculosis bacillus, the macrophages and sensitized lymphocytes are activated, causing a specific immune response in the body, thereby resisting the infection by the tuberculosis bacillus. Therefore, the BCG vaccine mainly prevents pulmonary tuberculosis.

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Infectious Disease
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How long can someone with tuberculosis live?

Early detection and appropriate anti-tuberculosis treatment of tuberculosis can lead to a normal lifespan once cured. However, it is important to exercise regularly and enhance immunity, since tuberculosis may recur if the body's resistance decreases. With the increase of drug-resistant tuberculosis, treatment difficulties have intensified. If it is detected late or not treated properly and the lung damage progresses to an advanced stage, it can be life-threatening, with survival ranging from days to years. When tuberculosis involves massive hemoptysis, death can occur at any time due to suffocation or hemorrhagic shock, depending on the specific condition.