Tuberculosis (TB) is an infection caused by the bacteria Mycobacterium tuberculosis. It most commonly affects your lungs but can affect other parts of your body as well, such as your bones or lymph nodes.
At present, a third of the world’s population (more than 2 billion people) are infected with the bacteria that cause tuberculosis. However, only one in 10 infected people will show signs of the disease. This is known as active tuberculosis.
Tuberculosis occurs most often in major cities. This is because there are more risk factors for tuberculosis in cities, such as overcrowded housing and more people visiting from other countries that may have a higher rate of tuberculosis. Tuberculosis is the second leading cause of death from an infectious disease worldwide, after HIV/AIDS.
Symptoms of tuberculosis
You may or may not have any symptoms depending on how your body reacts to the tuberculosis infection. Once you have been infected with the tuberculosis bacteria, one of three things could happen.
• You won’t have any symptoms because your immune system kills the bacteria and clears the infection.
• You will have symptoms because your immune system can’t clear the infection and the bacteria begin to grow in your lungs or other organs.
• You will get symptoms only if the infection is reactivated, which may be many years later. This is because your immune system builds a defensive wall around the bacteria, which is known as a latent infection.
If you have any symptoms of tuberculosis in your lungs, these can include:
• a persistent cough, which may produce phlegm with or without blood in it
• loss of appetite
• weight loss
• fever (high temperature)
• night sweats
• chest pain when you breathe in, caused by inflammation of the membranes lining your lungs (pleurisy)
You may have tuberculosis infection in a part of your body other than your lungs. Your symptoms will depend on where the infection is. You may have:
• swollen neck glands
• bone pain, joint pain and swelling, or back pain
• abdominal (tummy) pain
• confusion, problems with your vision or a persistent headache
• skin sores
• breathlessness and chest pain
• ankle swelling
These symptoms aren’t always caused by tuberculosis, but if you have them, see a doctor.
Causes of tuberculosis
You can be infected with tuberculosis bacteria when someone who is already infected coughs or sneezes. This produces droplets containing the bacteria that are then dispersed in the air. These bacteria can survive for long periods of time outside the body.
If you breathe in the bacteria that are in the droplets, they will usually begin to grow and multiply inside cells in your lungs. If they enter your blood, they can be transported to other organs, such as your brain or stomach, and start growing in these parts of your body as well.
You’re at a higher risk of catching tuberculosis if you:
• live in or come from an area with a high rate of disease (for example, sub-Saharan Africa, South East Asia and Eastern Europe)
• have close contact with someone who has active tuberculosis (this would include anyone living in the same house as you, or a colleague working closely with you)
• have had previous (especially incomplete) treatment for tuberculosis
• have another long-term disease such as HIV/AIDS, diabetes or kidney failure
• are taking a long course of corticosteroids, or are having chemotherapy
• are young or elderly
• are homeless, or living in overcrowded conditions or an institution, such as a hospital or care home
• are dependent on alcohol or illegal drugs
However, tuberculosis isn’t spread by:
• shaking hands
• sharing food or drink
• touching bed linen that someone with tuberculosis has used
• sharing toilet seats
• sharing toothbrushes
Diagnosis of tuberculosis
If you think you have tuberculosis, see your doctor, who will ask you about your symptoms and examine you. He or she may also ask you about your medical history. If your doctor thinks you have tuberculosis, he or she will carry out some tests to confirm this. You may need to have some tests in hospital.
Tests for tuberculosis include the following.
• Chest X-ray. This is to look for signs of infection in your lungs.
• Phlegm (sputum) samples. You will be asked to provide three samples of phlegm that you cough up, not just saliva – these are sent to a laboratory to test for bacteria. As well as being used for diagnosis, these tests can help to find out which antibiotics will be the most effective against the bacteria.
• Mantoux test. In this test, your doctor will inject a protein from the tuberculosis bacteria just under the skin in your forearm, to test how your body reacts. If you have been exposed to tuberculosis, you may develop a hard lump at the injection site.
The stronger the reaction, the greater the chance that you have been exposed to tuberculosis. If you have previously had a BCG vaccination to protect you against tuberculosis, the results may not be as reliable.
• Bronchoscopy. In this test, your doctor uses a flexible tube with a telescopic light and camera at the end, to see down your airways and into your lungs.
• CT scan. This uses X-rays to make a three-dimensional image of your body or part of your body. You’re more likely to have this if your doctor thinks that you have tuberculosis in organs other than your lungs.
Please note that availability and use of specific tests may vary from country to country.
Treatment of tuberculosis
Treatment for tuberculosis usually involves taking antibiotics every day for six months. The reason for the long course of treatment is because the bacteria that cause tuberculosis are often in a dormant state (not growing or multiplying). Antibiotics work best on bacteria that are growing and multiplying, so in order to try to kill all the bacteria, a long course of treatment is needed.
The treatment involves using different antibiotics to help prevent the bacteria becoming resistant – this means that the antibiotics become less effective. You’re likely to be given four different antibiotics to take every day for two months. After this you will be given two different antibiotics to take daily for the next four months. Talk to your doctor about the best way to make sure you get the right treatment.
Always ask your doctor for advice and read the patient information leaflet that comes with your medicines.
Sometimes, resistance can start when the bacteria causing an infection aren't completely killed off by an antibiotic. Some bacteria survive because they have a genetic mutation that helps them resist the treatment. The few bacteria that survive can then multiply, causing an infection that is resistant to that particular antibiotic.
There are different levels of drug resistance that can happen in tuberculosis treatment.
• Single drug-resistant tuberculosis. This means that the bacteria are resistant to one of the antibiotics used to treat the infection. You will need to take an alternative antibiotic instead.
• Multidrug-resistant tuberculosis. This means that the bacteria are resistant to the two most effective antibiotics. You will need to take alternative antibiotics instead.
• Extensively drug-resistant tuberculosis. This means the bacteria are resistant to the most effective antibiotics and the ones used for multidrug-resistant tuberculosis. This form of tuberculosis is therefore very difficult to treat.
• Totally drug-resistant tuberculosis. This is the newest form of resistant tuberculosis and is still very rare. The bacteria are resistant to up to 10 different antibiotics.
Getting these types of tuberculosis is more likely if you don’t take the full course of antibiotics in the way these were prescribed for you. A failed course of antibiotics increases the chance that tuberculosis will come back again and be more difficult to treat.
Availability and use of different treatments may vary from country to country. Ask your doctor for advice on your treatment options.
Prevention of tuberculosis
The most effective way to protect against tuberculosis is immunisation with the BCG vaccine. The BCG vaccination is recommended if you:
• are more likely to be exposed to tuberculosis (for example, if you’re a healthcare worker)
• are travelling to or living in an area with a high rate of tuberculosis infection
• are in close contact with someone who has been diagnosed with tuberculosis