Does tuberculosis infect people?

Written by Han Jian Hua
Infectious Disease
Updated on September 07, 2024
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Tuberculosis is a contagious disease, and hearing the term "tuberculosis" inevitably makes people nervous. However, not all tuberculosis patients are contagious. Research shows that among tuberculosis patients, only those who have tuberculosis bacteria found in sputum smear tests are contagious. With a source of infection, the tuberculosis bacteria must be transmitted to others through certain routes. Airborne transmission is the main route of transmission for tuberculosis bacteria. When a tuberculosis patient coughs, sneezes, or speaks loudly, they release a large number of droplet nuclei containing tuberculosis bacteria into the air, which can be inhaled by healthy individuals and cause infection. The degree of tuberculosis bacteria infection mainly depends on factors such as the amount of bacteria the patient expels, the severity of coughing symptoms, and the extent of contact. Therefore, when there is a tuberculosis patient nearby, we first need to understand whether they are in the active phase of the disease, that is, expelling bacteria, and whether they are undergoing anti-tuberculosis chemotherapy. If the patient has a negative sputum test or has undergone chemotherapy for a positive sputum test, such patients have very low contagiousness, so there is no need to worry too much about being infected.

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Does tuberculosis cause fever?

Does tuberculosis cause fever? The answer is definitely yes. Fever is one of the most common clinical manifestations of tuberculosis. Many tuberculosis patients experience low fevers, and a minority of patients, such as those with caseous tuberculosis or tuberculous pleurisy, may experience high fevers that can recur and persist. Moreover, tuberculosis patients may sometimes also have concurrent bacterial infections, which can cause the fever to last longer and be more difficult to control.

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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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How is tuberculosis diagnosed?

The diagnosis of tuberculosis primarily involves combining relevant clinical symptoms, such as whether there is cough, expectoration, low fever, night sweats, and blood in phlegm. It also requires considering the patient's chest imaging features, whether there is obvious infection, fresh exudation, cavities, as well as sputum tests. For example, if the sputum stain for acid-fast bacilli is positive, and the sputum culture is positive, using these comprehensive diagnostic methods, tuberculosis can be diagnosed, after which anti-tuberculosis treatment should be initiated.

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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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How to test for tuberculosis

To examine pulmonary tuberculosis, it is essential to understand that it pertains to tuberculosis changes in the lung tissue, airways, bronchi, and pleura. The pathogen causing tuberculosis is Mycobacterium tuberculosis, also known as the tubercle bacillus. There are multiple tests available for people with pulmonary tuberculosis, as the disease can vary based on location and type. Therefore, such patients generally require numerous tests. The most commonly used are imaging studies for the chest, including X-rays and CT scans. In imaging studies, most patients will show some lesions, but there are instances where tuberculosis in the airways and bronchi might not be clearly visible on CT or X-rays, necessitating more invasive tests like bronchoscopy. Additionally, bacteriological examinations, such as sputum smear and pleural fluid smear, as well as culture for Mycobacterium tuberculosis, are typically conducted for patients. Nowadays, hospitals equipped with the necessary facilities conduct molecular biological tests, namely nucleic acid testing for Mycobacterium tuberculosis DNA. Furthermore, some patients with complex conditions may require a histopathological biopsy, commonly referred to as tissue sampling, at the site of the lesion to observe under a microscope for characteristic changes indicative of tuberculosis. There are also immunological tests that assist in diagnosing tuberculosis, such as the gamma interferon release assay (commonly known as the T-SPOT), tuberculin skin test, and traditional antibody tests against Mycobacterium tuberculosis.