Tuberculosis

Tuberculosis - What it is

Tuberculosis - Conditions & Treatments SingHealth

Tuberculosis, or TB for short, is a disease caused by bacteria called Mycobacterium tuberculosis. TB is a serious disease that can cause a person to become very sick if not treated properly with medicines.

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, kidneys, intestines, covering of the heart known as the pericardium, brain, and liver.

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).

How is tuberculosis spread?

TB is spread through the air from one person to another. The TB bacteria is passed through the air when someone who is sick with TB disease coughs, laughs, sings, or sneezes. When you breathe air that has the TB bacteria, you may get TB infection (latent TB). This means you have dormant (sleeping) TB bacteria in your body that does not make you sick and cannot be passed to anyone else. If these dormant TB bacteria wake up and multiply, you will get sick with TB disease (active TB).

If you have TB infection, the chances of getting TB disease increases if you have HIV infection or other health problems such as diabetes that make it difficult for your body to fight bacteria. If you abuse alcohol or use illicit drugs, or you were not treated correctly for TB infection in the past, your risk of getting TB disease increases as well.

You cannot get TB bacteria from sharing drinking containers or eating utensils, sharing cigarettes, or saliva shared from kissing.

Can tuberculosis affect other parts of the body?

TB usually affects the lungs, but it can also affect other parts of the body such as lymph nodes, bones and joints, kidneys, intestines, covering of the heart known as the pericardium, brain and liver.

Tuberculosis - Symptoms

Patients with tuberculosis disease (active TB) may complain of persistent cough, sometimes this may be productive of blood-stained sputum, fever and chills, night sweats, loss of appetite, loss of weight, and easy fatigability.

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

A screening chest radiograph can be done. Though a normal radiograph does not exclude tuberculosis, there is a much lower likelihood of having tuberculosis disease (active TB) of the lung if the radiograph is normal. 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 be 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

Tuberculosis disease (active TB) can be treated very effectively with a combination of appropriate drugs. Treatment may take up to 6 months or more, but as long as they are taken as prescribed, the disease usually can be cured. 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.