Tuberculosis

Health and Nutrition > Diseases > T Reviewed by Dr Gavin Petrie, consultant respiratory physician

What is tuberculosis?

Tuberculosis is a disease caused by an infection with the bacteria Mycobacterium tuberculosis.

During the 19th century, up to 25 per cent of deaths in Europe were caused by this disease. The death toll began to fall as living standards improved at the start of the 20th century, and from the 1940s, effective medicines were developed.

However, there are now more people in the world with TB than there were in 1950, and 3 million individuals will die this year from this disease - mainly in less developed countries.

The disease is more common in areas of the world where poverty, malnutrition, poor general health and social disruption are present.

In the UK, too, the number of TB cases is again rising. Alcoholics, HIV-positive individuals, some recent immigrants and healthcare workers are at increased risk.

The disease is most commonly found in places such as hostels for the homeless, prisons, and centres for immigrants arriving from areas with high rates of HIV infection or inadequate health provision.

What parts of the body are affected by tuberculosis?

First and foremost, tuberculosis is a disease of the lungs. However, the infection can spread via blood from the lungs to all organs in the body. This means that you can develop tuberculosis in the pleura (the covering of the lungs), in the bones, the urinary tract and sexual organs, the intestines and even in the skin.

Lymph nodes in the lung root and on the throat can also get infected.

Tuberculous meningitis is sometimes seen in newly infected children. This form of the disease is a life-threatening condition.

How do you catch tuberculosis?

The bacteria that cause the disease are inhaled in the form of microscopic droplets that come from a person with tuberculosis. When coughing, speaking or sneezing, the small droplets are expelled into the air. They dry out quickly, but the bacteria itself can remain airborne for hours. However, the tuberculosis bacteria are killed when exposed to ultraviolet light, including sunlight.

How does the disease develop inside the body?

After the tuberculosis bacteria have been inhaled they reach the lungs and, within approximately six weeks, a small infection appears that rarely gives any symptoms. This is called a primary infection.

After this, the bacteria can then spread through the blood. If you have a healthy immune system, in most cases the infection will remain dormant without doing any obvious harm.

Months or even years later, however, the disease can become reactivated in different organs if the immune system is weakened. The lungs are the favourite place for the illness to strike.

What are the symptoms?

Typical signs of tuberculosis are:

- chronic or persistent cough and sputum production.

If the disease is at an advanced stage the sputum will contain blood.
- fatigue.
- lack of appetite.
- weight loss.
- fever.
- night sweats.

Tuberculosis can mimic many forms of disease and must always be considered if no firm diagnosis has been made.

Other non-tuberculous mycobacteria found in soil and water can cause disease in susceptible patients with a history of cystic fibrosis, chronic lung damage, alcoholism and immunosuppression (suppression of immune responses by a disease or drugs). These atypical mycobacteria can be present as colonising organisms without necessarily causing disease.

When should I see a doctor?

. If you have a persistent cough with sputum for more than three weeks, you should contact your doctor.

How does the doctor make the diagnosis?

The doctor cannot always hear enough to make a diagnosis by just using a stethoscope. If your physician suspects there is something wrong and that it is not just a cold, you may be referred to an outpatient department for people with lung diseases or to an X-ray department.

The chest X-ray examination is the most important test. If there are changes in the lungs, a sample of sputum will be sent for microscopic examination and culture.

Culture of tuberculosis bacteria will take 4 to 12 weeks. For this reason, it takes some time before an accurate diagnosis is possible.

Quicker methods using DNA techniques are under development, and a skin reaction Mantoux Test can sometimes be a great help. In this test, Tuberculin, which is a substance extracted from the tubercle bacteria, is injected into the skin. If the skin shows a strong reaction after 72 hours, it means there is hypersensitivity to tuberculin protein acquired either by a previous BCG vaccination, or possibly due to an active infection.

The documents contained in this web site are presented for information purposes only. The material is in no way intended to replace professional medical care or attention by a qualified practitioner. The materials in this web site cannot and should not be used as a basis for diagnosis or choice of treatment. Conditions for use

© Copyright 1998 - 2009 NetDoctor.co.uk - All rights reserved