Tuberculosis is caused by a bacterium. It may cause disease in any part of the body but the lung is the usual site, where the bacterium slowly destroys the tissue of the lungs - this is called pulmonary tuberculosis. Only TB of the lungs or throat can be - but are not always - infectious.

The most common symptoms of pulmonary tuberculosis are:

• A cough that lasts for more than three weeks.  This may start as a dry irritating cough, which may be no different from that suffered in any chest infection. The cough of tuberculosis will continue for weeks or months getting progressively worse. After a while profuse amounts of phlegm may be brought up from the chest with each cough. If a blood vessel is damaged blood may be coughed up. The cough of severe tuberculosis may be uncontrollable causing the patient to have spasms of wracking continuous coughing.Sometimes the patient will complain of pains in the chest which will be made worse by coughing. In severe cases, where much of the lung has been destroyed, breathlessness may occur.
• Loss of weight for no obvious reason - initially losing weight very slowly but often realising after some months that he is many kilograms lighter
• Fever and heavy night sweats. Temperatures which accompany the disease often occur at night causing the patient to sweat profusely, so badly that it may be necessary to change all the bed clothes in the middle of the night.
• A general and unusual sense of tiredness and being unwell
• Loss of appetite

All of these symptoms may be signs of other problems, but if you have them and are worried you should talk to a doctor or nurse at your local surgery or clinic.