Tuberculosis (TB) is a disease caused by infection with a germ called Mycobacterium Tuberculosis. TB can affect any part of the body, but most commonly the lungs and the gut (gastrointestinal tract) which are places where the germs can easily get into the body.

Immunisation and the introduction of treatments with drugs (antibiotics) have played a part in making TB less common in the West in the latter part of the 20th Century, but better hygiene, nutrition and standard of living have probably been more important than either of these.

Worldwide, tuberculosis is still very common. About a third of the world's population is infected with TB, and it kills more people than any other infection. In the past TB was known as consumption and until the era of antibiotics all that was available for treatment was long stays in special hospitals (sanitoria). Here people were given plenty of fresh air and physical treatments such as collapsing their lungs.

These days it is possible to immunise people to protect them against TB, and if you get it you can be treated with antibiotics. It need not be as frightening as it once was, but unfortunately there are some "superbugs" developing. These take the form of TB which is resistant to the antibiotics that are usually used. It is therefore important to receive treatment and to complete the course of treatment under medical supervision.

The main symptoms of TB are:

• Fever
• Sweats
• Weight loss

Other symptoms depend on the part of the body that is affected. The lungs are most often affected by tuberculosis (pulmonary tuberculosis), which tends to cause a persistent cough.

Active TB

TB may become active in about 10% of people who are infected. This is more likely to happen as you get older, when your immunity is low, as in malnutrition, when you are taking drugs that suppress the immune system, including long term steroids and anti-cancer drugs, and in conditions that lower your immunity, such as leukaemia and HIV. Diabetes also makes you more susceptible to TB.

If TB becomes active, you are more likely to to have the typical symptoms. If you have active TB it is important to seek treatment and to complete the treatment as directed by your doctor. Not only can the condition be very debilitating and fatal to you, but you are also infectious and can spread it to other people. Treatment is usually fairly straightforward and you will be non-infectious after being on treatment for two weeks. (You will, however, usually need to take the treatment for three to six months.)

Tuberculosis is caused by an infection with bacteria (Mycobacterium Tuberculosis). There are a number of different tuberculosis germs (bacteria), and apart from the human form, which is most often the cause, we can also be affected by one which affects cattle (Bovine TB).

Spread of the human TB is via "droplet" infection. Coughs and sneezes and even talking releases these droplets and can spread TB, but only if the person has active TB. Droplets of a certain size are breathed right into the lungs, where they can multiply and lead to infection. It would usually, however, follow prolonged, close contact.

As well multiplying in the lungs, some of the germs may travel to other parts of the body such as the bones, and the kidneys. The body's natural defences fight the infection, but cannot usually get rid of all the germs. These defences wall off the affected areas (in capsules which were called tubercles and led to the name tuberculosis) where the germs can lie inactive, while the person is otherwise well. It is as though the body is in a "standoff" situation with the bacteria.

In such circumstances the person has a TB infection, but is not infectious to others. Treatment with drugs (antibiotics) will stop such a person developing active TB.

Although tuberculosis bacteria can be detected on surfaces in a room where an infectious sufferer lives, they are not likely to infect someone who uses the room, as they are not likely to get into the lungs in adequate quantities.

Bovine Tuberculosis can be picked up from unpasteurised milk from an infected cow. Milk herds are regularly tested, and anyway, pasteurisation is enough to kill the tubercle germs (bacteria). If, however you drink untreated milk from an infected cow the germs can get into your system and may lead to infection building up in the gut.

Poverty, homelessness and a poor provision of health services lead to an increased risk of catching Tuberculosis. The number of deaths from TB in the developed countries started to drop in the early twentieth century before immunisation and antibiotics. That was probably largely due to improvement in these social factors.

As well as asking you about your symptoms and examining you, your doctor is likely to arrange other tests depending on where they think the main problem is. Most commonly this will mean a chest X-ray and a laboratory test of the sputum you cough up. It may mean urine tests and possibly other X-rays. Another test involves giving you an injection into the skin of your arm to see if the body reacts to it (tuberculin test).

Usually the diagnosis is made when one or more of these confirms TB.

Your doctor is likely to refer you to a specialist. Usually you will be taking a combination of antibiotics for three to six months. Occasionally the bacteria are resistant to two or more of the main antibiotics (multidrug-resistant TB or MDR-TB). If this happens your doctor will use alternative combinations of drugs over a period of up to two years.

The success of the treatment should be noticeable by an improvement in how you feel. Fever and sweats should go, weight should come back on, and cough should improve. Your doctor will check for disappearance of the bacteria in samples (of sputum, in the case of pulmonary TB, or urine, in the case of renal tract TB) and an improvement in X-ray appearance. When it is confirmed that you are cured you will be allowed to stop your medication.

Until then it is vital that you continue taking your medication, for your own sake and that of your community. If you have any side effects or other problems with the treatment discuss them with your doctor.

The following are important to help prevent tuberculosis:

• Better living conditions and standards of hygiene help to reduce the overall prevalence of TB.
• Immunisation with BCG vaccine is used in the UK, where it is given to children between the ages of 10 and 14 years, and babies who are considered at higher risk of coming into contact with someone with active TB. It is said to be more than 70% effective at preventing active TB. However it does make the tuberculin test positive, which reduces the value of this test in diagnosis.
• Many countries check immigrants for TB, treating active TB and immunising, if that is the local policy, if the tuberculin test is negative.
• More awareness of the possibility of TB in the high risk groups.

• Health Protection Agency
• WHO Global tuberculosis control
• TB Database