Tuberculosis (TB)

What is Tuberculosis?
Tuberculosis or "TB" is a disease caused by a bacterium (germ) called Mycobacterium tuberculosis. TB usually affects the lungs but it can also affect other parts of the body, including the glands, the bones and rarely the brain.

Tuberculosis used to be more common in Ireland. There were nearly 7000 cases a year in the early 1950s. The incidence of TB has declined steadily since then. In 2005, there were 450 cases notified in Ireland. Doctors are obliged to notify each case of TB to the local Departments of Public Health in the Health Service Executive.

TB disease is preventable and curable.

What are the symptoms of TB?
Symptoms of TB can include any of the following:

• Fever and night sweats
• Cough (generally lasting more than 3 weeks)
• Weight loss
• Blood in the sputum (phlegm) at any time

A person with any of these symptoms should visit their family doctor for advice.

How is TB spread?
TB is usually spread in the air from another person who has TB of the lungs. It is spread by that person coughing, sneezing or spitting. People with TB in the lungs or throat can be infectious. This means that the bacteria can be spread to other people. Even then close and prolonged contact with such a person (i.e. family, friends, childminder, co-worker) is needed to become infected. Most cases of infectious TB stop being infectious after about 2 weeks of treatment. TB in other parts of the body such as the kidney or spine is usually not infectious.

Another type of TB called Mycobacterium bovis can arise from drinking contaminated milk. This form of TB is now rare, as pasteurisation of milk removes the risk.

The following people have a greater chance of becoming ill with TB, if exposed to it:

• Those in very close contact with infectious people
• Children
• Elderly people
• Diabetics
• People on steroids
• People on other drugs affecting the body's defence system
• People who are HIV positive
• People in overcrowded, poor housing
• People dependent on drugs or alcohol
• People with chronic poor health.

What is the difference between latent tuberculosis infection and active tuberculosis disease?
Infection with the TB bacterium may not develop into TB disease. Most people who are exposed to TB are able to overcome the bacteria. The bacteria become inactive, but they remain dormant in the body and can become active later. This is called latent TB infection.

People with latent TB infection:

• Have no symptoms
• Don't feel sick
• Can't spread TB to others
• Usually have a positive skin test reaction
• Can develop TB disease later in life.

Most people who have latent TB infection never develop active TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease. But in other people, who have weak immune systems, the bacteria can become active and cause active TB disease.

The Difference between Latent TB Infection and Active TB Disease

• A skin test
• A chest X-ray
• A test of the sputum (phlegm)
• A blood or urine test.

Can TB be treated?
Yes, today TB is potentially completely curable, if the responsible organism is fully sensitive to the antibiotics being used and the patient takes his or her medication as prescribed.

It is treated with tablets, which must be taken for about 6 months. Without treatment, many people used to die from TB. It is essential to take the treatment regularly and to complete the course as prescribed.

How important is treatment?
Treatment is very important. If you have TB disease or if you have been infected with the TB bacterium but have not yet become unwell i.e. have latent TB infection, you must take the treatment as directed. It is very important to complete the full course of treatment as it will stop you being infectious and it will remove the risk of you developing drug-resistant TB. It is important to remember that TB used to kill people before we had modern treatments.

What should I do, if I have been in contact with someone with TB?
Discuss this with your family doctor. Only close contacts are at risk of catching TB. You may be asked to attend a chest clinic, and to have a skin test and/or a chest X-ray. Sometimes a doctor or nurse will contact you first (they will have a list of close contacts of the person who has TB). This does not necessarily mean that you have TB, but is a chance to check for it, so it is very important to attend if you are asked to.  
 
Can TB be prevented?
Yes it can, in several ways:

1. Treating all people with active TB disease promptly. After two weeks of treatment, most patients are no longer infectious to other people.
2. Ensuring that all close contacts of people with TB are seen promptly in the chest clinic. Those found to have latent TB infection or those at high risk of developing TB after close contact may be offered a course of preventive therapy (chemo prophylaxis) once active TB has been ruled out.
3. Vaccination: In Ireland the BCG vaccination (vaccine against TB) is recommended for newborn babies. It is also recommended for those aged 10-15 years whose tuberculin skin test is negative and have had no previous BCG. BCG is also given to adults who are considered to be at risk of developing TB where potential contact with the disease could occur or has occurred. BCG vaccine is very effective, particularly in preventing childhood TB and the more severe forms of TB.

What are Multi-drug Resistant TB (MDR TB) and Extensively Drug Resistant TB (XDR-TB)?  

Multi-drug resistant TB (MDR TB)
MDR-TB is a specific form of TB which is resistant to at least isoniazid and rifampicin, two of the main first line drugs used in the treatment of TB. MDR-TB therefore is much more difficult to treat. It takes longer to treat with second line drugs which are more expensive and have more side-effects.

Extensively Drug Resistant TB (XDR-TB)
XDR-TB is a rare type of MDR-TB which is also resistant to any of a group of drugs called fluoroquinolones and at least one of three injectable second line anti-TB drugs (capreomycin, kanamycin or amikacin). Because XDR-TB is resistant to first line and second line drugs, treatment options are more limited. This revised definition of XDR-TB was agreed by the World Health Organization (WHO) Global Task Force on XDR-TB in October 2006.

Finalised Irish figures for TB cases in 2005 report that only two (0.4%) TB cases were classified as multi-drug resistant (MDR). One case of XDR-TB was notified during 2005. This is the first XDR-TB case notified in Ireland. There is no suggestion that XDR-TB cases are increasing in Ireland.

Further information on XDR-TB can be found on the WHO website.

Click here to see factsheet in other languages.

Last revised: 11 January 2008