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Tuberculosis

Tuberculosis - What it is

Tuberculosis is caused by infection from the microbe, Mycobacterium tuberculosis. Although the most common site of infection is the lung, tuberculosis may also cause infections in other parts of the body, such as bone, joints, lymph nodes, gastrointestinal tract and the brain. 

Not all persons develop tuberculosis when exposed to the Mycobacterium tuberculosis. Once exposed, some people may not develop tuberculosis, others develop latent infection (where there are no signs and symptoms) and others develop active infection (either early after exposure or many years later when the latent tuberculosis reactivates). 

Tuberculosis - Symptoms

As mentioned earlier, people who develop latent infection are asymptomatic. Although you may be exposed to the microbe, Mycobacterium tuberculosis may remain dormant or asleep and do not cause problems. 

When active infection develops, it typically runs a sub-acute to chronic course. You may experience non-specific constitutional symptoms such as fatigue, unexplained weight loss and loss of appetite, night sweats and intermittent fevers. 

More specific symptoms would depend on the site of the actual disease. For example, in tuberculosis infection of the lung, you may experience prolonged cough and sputum production; and in lymph node disease, you may experience swelling of the lymph nodes. 

Tuberculosis - How to prevent?

Childhood BCG (Bacillus Calmette-Guerin) vaccination is part of childhood vaccination in Singapore. BCG vaccination when administered during childhood is effective for the prevention of disseminated tuberculosis and tuberculosis meningitis from developing in children, and may also reduce the risk of development of active tuberculosis in adulthood. However, BCG vaccination only provides partial protection. 

You can still develop tuberculosis even if you have previously received the BCG vaccination in childhood. 

For public health considerations, only those with active tuberculosis in the lungs/airways can spread it in the community through their respiratory secretions. When a person with active tuberculosis in the lungs/airways coughs, the microbe, Mycobacterium tuberculosis, can be aerosolized and therefore be passed to other individuals around them. It is therefore very important for patients who have tuberculosis in the lungs/airways to be identified, diagnosed and treated early to prevent the spread of this infection in the community. 

Tuberculosis - Causes and Risk Factors

​The main risk factor would be exposure to a person who has active tuberculosis infection of the lungs/airways. The infected person’s cough expels respiratory droplets that contain tuberculosis and infection is contracted when this is inadvertently inhaled. When exposure occurs in a crowded setting or in enclosed spaces with poor ventilation, the risk of infection increases. 

Tuberculosis - Diagnosis

Latent tuberculosis is diagnosed by a skin test or a blood test. It is a measure of immunity against Mycobacterium tuberculosis. 

Active tuberculosis, on the other hand, is diagnosed by sending body fluid / tissue samples (e.g. blood, sputum, or body tissue) to the laboratory to be incubated. The diagnosis of active tuberculosis is confirmed when the incubated samples are found to positive for growth of Mycobacterium tuberculosis. This process may take up to 2 months as it is a slow growing organism. Nowadays, modern technology such as DNA testing has allowed for easier and more rapid diagnosis. Nonetheless, the diagnosis of active tuberculosis infection can remain difficult and all the available testing methods may still yield a negative result. In such cases, the diagnosis and management depends very much on the clinical acumen and judgement of the physician. 

Tuberculosis - Treatments

Latent tuberculosis treatment is usually with a single drug, and administered for a few months, the duration is dependent on the medication selected.

Active tuberculosis, however, needs to be treated with a combination of anti-tuberculosis medications. Treatment duration is prolonged and may run from 6 months or longer depending on the severity, site of the infection as well as the selection of medications used for the treatment of tuberculosis. Lung infection is usually treated for 6 months. The medications are taken orally once a day. During treatment, the physician will be closely monitoring the patient for any medication related side effects such as drug allergy, liver inflammation, kidney impairment or suppression of blood counts. As treatment course is prolonged, patients need to be reminded to be compliant to daily medications to prevent the development of treatment failure or drug resistant tuberculosis. 

When you are on tuberculosis medications, you need to inform your doctors of other medications that you are taking due to the possibility of drug interactions. 


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