Tuberculosis (TB) is an infectious disease caused by a bacterium called Mycobacterium tuberculosis. It’s a disease that usually affects lungs, but it can affect any other parts of your body such as your skin or other organs.
TB is passed on from person t person by droplets carried in the air, usually from coughs and sneezes. Your body’s immune system, which fights infection, usually destroys the germs once they are inhaled. In a small number of people, the immune system successfully builds a defensive barrier around the infection. The bacteria stay in the body, but you won’t usually have any symptoms and can’t pass the infection on to other people. This is called latent TB. Sometimes, the immune system fails to destroy the bacteria, or latent TB becomes active years later. This is more likely t happen if your immune system becomes weakened by other problems such as HIV, poorly controlled diabetes, or if you are underweight. At first, a TB infection normally affects the lungs. This is called pulmonary TB. However, TB often spreads to the lymph nodes (glands throughout your body that are part of your immune system). It can also affect your bones, joints and kidneys. TB can also cause meningitis (inflammation of the membranes surrounding the brain and spinal cord), though this is rare.
Causes of Tuberculosis
You can catch TB by breathing in droplets in the air that contain the bacterium M. tuberculosis. These are spread through the air when someone with TB coughs or sneezes. Only some people with TB in their lungs are infectious to others. Although it is spread through the air, you need to be closely exposed t a person with TB for some time before you catch it. People most commonly catch TB from people they live or work with. When you start treatment for TB, you remain infectious to others for the first two weeks.
Although anyone can get TB, it’s quite difficult to catch. You’re more likely t get TB if you:
- Already have a weakened immune system (for example, if you have HIV/AIDS or are taking medicines that suppress your immune system).
- Have diabetes.
- Have regular close contact with people who have TB lung infection.
- Are young or elderly.
- Live in overcrowded housing.
- Are dependent on drugs or alcohol.
- Are in poor health generally and have been for some time.
Symptoms Of Tuberculosis
- Depending on how effectively your immune system fights the infection, you may have:
- N symptoms at all.
- Minor symptoms, which then go as you fight the infection off.
- Symptoms that develop in the months following infection.
- Symptoms that develop years after you were infected.
The symptoms of tuberculosis infection in your lungs may include:
- A persistent cough – there may als be lots of phlegm, sometimes containing blood.
- Loss of appetite.
- Weight loss.
- Sweating, particularly at night.
- Chest pain when you breathe in, caused by inflammation of the membranes lining your lungs (pleurisy).
If you have TB in other parts of your body, you may also have other symptoms such as swollen glands in your neck, pain in your joints or a headache.
Diagnosis for Tuberculosis
If you come to a TB clinic, we sometime find that you do not have TB and there is another cause for your symptoms. If we think you have been exposed to TB, we will investigate to decide whether you have an active infection (evidence of infection on x-ray/ scans, suggestive symptoms and/or the presence of TB bacteria from samples) or latent TB which means the tests reveal evidence of exposure TB bacteria but an active disease.
To diagnose active TB infection, you will usually be asked to give at least three separate samples of your phlegm for testing. These will be examined in a laboratory to see if we can grow the tuberculosis bacterium from the samples. We will as routinely blood tests, including tests of liver and kidney function, and a chest X-ray to look for active TB in the lungs and enlargement of lymph glands of the chest.In some cases, if we are unable to grow the tuberculosis bacterium from your sputum samples but think that you have active tuberculosis in your lung, we may ask you to come in for the day for a bronchoscopy. This allows us to take a sample from deep in your lungs by passing a small flexible telescope (a bronchoscope) down the breathing tubes in order look for signs of infection and inflammation. If you have enlarged lymph nodes in your chest, we may perform an EBUS (endobronchial ultrasound) to take a sample of the lymph-nodes in the chest safely using a very special bronchoscope which avoids the need for an operation. Both bronchoscopy and EBUS are quick, safe and painless daycase procedures. If you have other swollen lymph glands, for example in your neck, that we think may be affected with tuberculosis, we may suggest a biopsy of one of these first as this is the easiest way to diagnose glandular TB. If you are diagnosed with active TB, those people who have been in close contact with you, such as family members or work colleagues, may also be tested for the infection.
To diagnose latent TB, you can have a skin test called a Mantoux. This test involves an injection just under your skin usually on the inside of your forearm. Over the next two to three days, a reaction to the injection will develop which is then graded. The greater the reaction, the more likely it is that you have TB exposure and, in this case, your doctor may ask you t have further tests t exclude active infection. This test may be positive if you have had a BCG immunisation against TB in the past. Latent TB can also be diagnosed with an Interferon Gamma Release Assay (IGRA) test that can be useful if you have had previous BCG immunisation.