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Tuberculosis (TB) is a bacterial infection. It is spread through inhaling tiny droplets of saliva from the coughs or sneezes of an infected person.

TB mainly affects the lungs. However, the infection can spread to many parts of the body, including the bones and nervous system.

Typical symptoms of TB include:

  • a persistent cough
  • weight loss 
  • night sweats

See Tuberculosis - symptoms for more information.

The bacteria responsible for TB are very slow moving, so TB develops slowly in the body. You may not experience any symptoms for many months or even years after being infected.

What happens if you are infected?

Three things can happen if you are infected with TB:

  • Your immune system (the body's natural defence against infection and illness) kills the bacteria and you have no further symptoms. This happens in most cases. 
  • Your immune system cannot kill the bacteria, but manages to build a defensive barrier around the infection. This means that you will not have any symptoms, but the bacteria will remain in your body. This is known as latent TB. 
  • Your immune system fails to kill or contain the infection and it slowly spreads to your lungs. This is known as active TB.

Latent TB could develop into an active TB infection at a later date, particularly if your immune system becomes weakened.


If it is not treated, an active TB infection can be fatal. It can damage the lungs to such an extent that a person cannot breathe properly.

With treatment, a TB infection can usually be cured. Most people will need to take a long-term course of antibiotics, which usually lasts for at least six months. See Tuberculosis - treatment for more information.

However, TB can sometimes be fatal even with treatment.


The Bacillus Calmette-Guérin vaccine, also known as the BCG vaccine, can protect against TB. The BCG vaccine provides effective protection against TB in up to 8 out of 10 of people who are given it.

BCG vaccination is routinely given as part of the childhood vaccination schedule.

Vaccinations may also be recommended for people who have an increased risk of developing a TB infection. This includes health workers who may be exposed to TB and children who have recently arrived from countries that have high levels of TB.

See Tuberculosis - prevention for more information about the BCG vaccination.

How common is TB?

Before antibiotics were introduced, TB was a major health problem in Ireland. Nowadays, the condition is much less common. Provisional figures from the Health Protection Surveillance Centre for 2010 indicate that there was an 11% decline in the number of cases of tuberculosis notified (427) compared with 479 in 2009.

Countries with high numbers of HIV cases often have high numbers of TB cases. This is because HIV weakens a person's immune system, which means they are more likely to develop a TB infection.

It is also estimated that one-third of the world's population is infected with latent TB. Up to 1 in 10 of people with a latent TB infection (but who do not have HIV) will develop active TB at some point.

Countries with high TB rates

Parts of the world that have high rates of TB include:

  • Africa - particularly sub-Saharan Africa (all the African countries that are south of the Sahara desert) and West Africa, including Nigeria and South Africa 
  • Southeast Asia - including India, Pakistan, Indonesia and Bangladesh
  • Russia
  • China 
  • South America 
  • the western Pacific region (to the west of the Pacific Ocean) - including Vietnam and Cambodia

Tuberculosis (TB) will not cause any symptoms until the infection has reached the lungs. As the bacteria are very slow moving, the condition develops very slowly. Your symptoms might not begin until many years after you were initially exposed to the bacteria.

Pulmonary tuberculosis (TB)

A TB infection of the lungs is known as pulmonary TB. In Ireland , just under two-thirds of the TB cases in 2010 were pulmonary TB.

Symptoms of pulmonary TB include:

  • a persistent cough that brings up thick phlegm, which may be bloody 
  • breathlessness, which is usually mild to begin with and gradually gets worse
  • weight loss
  • lack of appetite
  • a high temperature of 38C (100.4F) or above
  • night sweats
  • extreme tiredness
  • a sense of feeling unwell

When to get medical help

Always see your GP if you have a cough that lasts for more than three weeks or if you cough up blood.

Extrapulmonary tuberculosis (TB)

In some cases, a TB infection can spread from the lungs to other parts of the body. TB infections that occur outside the lungs are known as extrapulmonary TB.

Extrapulmonary TB is more common in people with weakened immune systems (the body's natural defence against infection and illness), particularly people with HIV infection.

A TB infection can spread to:

  • lymph nodes that are near the lungs (lymph node TB)
  • bones and joints (skeletal TB)
  • the digestive system (gastrointestinal TB)
  • the bladder and reproductive system (genitourinary TB)
  • the nervous system (central nervous system TB)

These types of extrapulmonary TB can cause additional symptoms, which are described below.

Lymph node TB

Lymph nodes are small, oval glands that are part of the immune system. They remove unwanted bacteria and particles from the body. Symptoms of lymph node TB include:

  • persistent, painless swelling of the lymph nodes, which usually affects nodes in the neck, but swelling can occur in nodes throughout your body 
  • over time, the swollen nodes can begin to release a discharge of fluid through the skin

Skeletal TB

Symptoms of skeletal TB include:

  • bone pain
  • curving of the affected bone or joint
  • loss of movement or feeling in the affected bone or joint
  • weakened bone that may fracture easily

Gastrointestinal TB

Symptoms of gastrointestinal TB include:

  • abdominal pain
  • diarrhoea
  • bleeding from your anus

Genitourinary TB 

Symptoms of genitourinary TB include:

  • a burning sensation when you pass urine
  • blood in your urine
  • a frequent urge to pass urine during the night
  • groin pain

Central nervous system TB

Your central nervous system consists of your brain and spinal cord. TB can cause meningitis. Symptoms of central nervous system TB include:

  • headaches
  • being sick 
  • stiff neck
  • changes in your mental state, such as confusion
  • blurred vision
  • fits

Tuberculosis (TB) is caused by a type of bacterium called Mycobacterium tuberculosis.

TB is spread when a person with an active TB infection in their lungs coughs or sneezes and someone else inhales a droplet of contaminated saliva.

However, although it is spread in the same way as a cold or the flu, TB is not as contagious. You would usually have to spend at least eight hours in close contact with an infected person before you developed a TB infection yourself.

For example, TB infections usually spread between family members who live in the same house. It would be highly unlikely to become infected by sitting next to an infected person on a bus or train.

Risk factors for TB

Anyone can catch TB, but people who are particularly at risk include:

  • people living in environments where the level of existing TB infection is higher than normal
  • people with health conditions (such as HIV) or whose circumstances mean they are less able to fight off a TB infection

The known risk factors for an active TB infection include:

  • being in close contact with someone who is infected
  • having lived in, travelled to or had visitors from parts of the world where TB is common (see Tuberculosis - introduction for more details)
  • being part of an ethnic minority community that originated in parts of the world where TB is still common
  • having an immune system (the body's natural defence against infection and illness) that has been weakened by HIV, diabetes or other medical conditions
  • having an immune system that has been weakened by long courses of medication, such as corticosteroidschemotherapy or tumour necrosis factor blockers (used to treat some types of arthritis
  • being very young or very old - the immune systems of people who are young or elderly tend to be weaker than those of healthy adults
  • being in poor health or having a poor diet due to lifestyle and behavioural problems, such as drug misusealcohol misuse or homelessness
  • living in poor or crowded housing conditions, such as remand centres and prisons

Place of birth

In 2009, 43% of reoorted cases of tuberculosis were among people born outside Ireland.

Several tests are used to diagnose tuberculosis (TB). The test you have will depend on the type of TB that is suspected. Your GP may refer you to a TB specialist if they think that you have TB. 

Pulmonary TB

A diagnosis of pulmonary TB (TB that affects the lungs) can usually be confirmed with a chest X-ray. This uses high-energy radiation to create an image of your lungs. If you have a TB infection, changes to the appearance of your lungs, such as scarring, should be visible on the X-ray.

Samples of mucus and phlegm will also be taken and checked under a microscope for the presence of TB bacteria.

Extrapulmonary TB

If you have suspected extrapulmonary TB (TB that occurs outside the lungs), several tests can be used to confirm a diagnosis. These include:

  • computerised tomography (CT) scan - a series of X-rays of your body is taken at slightly different angles and a computer puts the images together to create a detailed picture of the inside of your body
  • magnetic resonance imaging (MRI) scan - a strong magnetic field and radio waves are used to produce detailed images of the inside of your body
  • ultrasound scan - high-frequency sound waves create an image of part of the inside of your body
  • blood test
  • urine test
  • biopsy - a small tissue sample is taken from the affected site and tested for the presence of disease

You may also have a lumbar puncture. This involves taking a small sample of cerebrospinal fluid from the base of your spine. Cerebrospinal fluid is a clear fluid that surrounds and supports the brain. The cerebrospinal fluid will be checked to see whether TB has infected your central nervous system.

Screening for latent TB

In some circumstances, you may need to be screened to check for a latent TB infection. This is when you have been infected with the TB bacteria but you do not have any symptoms.

For example, you may need to be screened if you have been in close contact with someone who is known to have an active TB infection, or if you have recently spent time in a country where TB levels are high.

If you you are a new entrant to Ireland ,or if you have returned from a country with a high incidence of TB it is recommended that you be screened for TB.

Mantoux test

The Mantoux test is a widely used test for latent TB. It involves injecting a substance called PPD tuberculin into the skin of your forearm.

If you have a latent TB infection, your skin will be sensitive to PPD tuberculin and a hard red bump will develop at the site of the injection, usually within 48 to 72 hours of having the test. If you have a very strong skin reaction, you may need to have a chest X-ray to confirm whether you have an active TB infection. 

If you do not have a latent infection, your skin will not react to the Mantoux test. However, as TB can take some time to develop, you may need to be screened again within a year.

If you have had the Bacillus Calmette-Guérin (BCG) vaccination, you may have a mild skin reaction to the Mantoux test. This does not mean that you have latent TB, but that your immune system (the body's natural defence against infection and illness) recognises the TB.

Interferon gamma release assay (IGRA)

The interferon gamma release assay (IGRA) is a newer type of blood test for TB that is becoming more widely available. 

The IGRA may be used to help diagnose latent TB:

  • if you have a positive Mantoux test 
  • as part of your TB screening if you have just moved to Ireland from a country where TB is common
  • if you are about to have treatment that will suppress your immune system, such as a type of medicine called tumour necrosis factor blockers 
  • if you are a healthcare worker 

Several medicines are used to treat tuberculosis (TB). Treatment usually lasts at least six months.

Pulmonary TB

If you are diagnosed with active pulmonary TB (TB that affects your lungs), you will probably be referred to a TB treatment team. This is a team of healthcare professionals with experience in treating TB.

Treatment team

Your TB treatment team may include: 

  • a respiratory physician - a doctor who specialises in conditions that affect the lungs and breathing
  • an infectious disease specialist
  • a public health doctor
  • a TB nurse 
  • a public health nurse - a qualified nurse with extra training who helps families with babies and young children to stay healthy
  • your GP
  • a paediatrician, if necessary - a doctor who specialises in conditions that affect children 

It is also likely that you will be assigned a key worker. This is usually a nurse or who will be the point of contact between you and the rest of the team and will help co-ordinate your care.


Pulmonary TB is treated using a six-month course of a combination of antibiotics. The usual course of treatment is:

  • two antibiotics - isoniazid and rifampicin - every day for six months 
  • two additional antibiotics - pyrazinamide and ethambutol - every day for the first two months

After taking the medicine for at least two weeks, most people are no longer infectious. However, it is very important to take your medicine exactly as prescribed and to complete the whole course of antibiotics.

It may be several weeks or months before you start to feel better. The exact length of time will depend on your overall health and the severity of your TB.

Taking medication for six months is the most effective method of ensuring that both the active and dormant TB bacteria are killed. The active bacteria are responsible for causing your current TB infection, but the dormant bacteria could become active in the future, so must also be killed.

If you stop taking your antibiotics before you complete the course, or if you skip a dose, the TB infection may become resistant to the antibiotics. This is potentially serious and can be difficult to treat. See Tuberculosis - complications for more information about drug-resistant tuberculosis.

Extrapulmonary TB

Extrapulmonary TB (TB that occurs outside the lungs) can be treated using the same combination of antibiotics as those used to treat pulmonary TB. However, you may need to take a 12-month course, rather than a six-month course.

If you have TB that affects your brain or heart, you may also be prescribed a corticosteroid, such as prednisolone, to take at the same time as your antibiotics. You will need to take the corticosteroid for several weeks.  

As with pulmonary TB, it is very important to take your medicines exactly as prescribed and to finish the course.

Latent TB

Latent TB is where you have been infected with the TB bacteria but you do not have any symptoms. Treatment for latent TB is usually recommended for:

  • people who are 35 years of age or under 
  • people with HIV, regardless of their age
  • people who are on immunosuppressive therapy
  • healthcare workers, regardless of their age 
  • people with evidence of scarring caused by TB, as shown on a chest X-ray, but who were never treated 

Treatment is not recommended for other people who are not on the list above and who have latent tuberculosis. This is because the risk of liver damage increases with age and the risks of treatment outweigh the benefits for some people.

In some cases, treatment for latent TB may be recommended for people taking immunosuppressant medication. This medication suppresses the immune system (the body's natural defence against illness and infection) and can make active TB more likely. This could include people taking long-term corticosteroids or people receiving chemotherapy.

Treatment for latent TB involves either taking a combination of rifampicin and isoniazid for three months, or isoniazid on its own for six months.

Side effects of treatment

Rifampicin can reduce the effectiveness of some types of contraception, such as the combined contraceptive pill. Use an alternative method of contraception, such as condoms, while taking rifampicin.

In rare cases, these antibiotics can cause damage to the liver or the eyes, which can be serious. Therefore, your liver function may be tested before you begin treatment. If you are going to be treated with ethambutol, your vision may also be tested.

Contact your TB treatment team immediately if you have any of the following symptoms:

  • feeling sick or being sick 
  • yellowing of your skin (jaundice) and darkening of your urine
  • unexplained fever - a temperature of 38C (100.4F) or above
  • tingling or numbness in your hands or feet
  • skin rash or itchy skin
  • changes to your vision, such as blurred vision or colour blindness

Supervised treatment

Sometimes people find it difficult to take their medication every day. If this affects you, your treatment team can work with you to find a solution.

This can include supervised treatment, which will involve regular contact with your treatment team (daily or three times a week) to support you taking your medication. This can take place in your home, the treatment clinic or somewhere else more convenient.

What if someone I know has TB?

When someone is diagnosed with TB, their treatment team will assess whether other people are at risk of infection. This may include close contacts, such as people living with the person who has TB, as well as casual contacts, such as work colleagues.

Anyone at risk will be asked to go for screening (see Tuberculosis - diagnosis).

Antibiotic-resistant tuberculosis (TB)

Like most bacteria, mycobacterium tuberculosis can develop a resistance to antibiotics. Antibiotic resistance means that the medicines can no longer kill the bacteria they are meant to fight.

Tuberculosis (TB) that develops a resistance to one type of antibiotic is not usually a concern because alternative antibiotics are available.

However, in an increasing number of cases:

  • TB develops a resistance to at least two antibiotics - this is known as multidrug- resistant tuberculosis (MDR-TB) 
  • TB develops a resistance to three or more antibiotics - this is known as extensively drug-resistant tuberculosis (XDR-TB)

  Both MDR-TB and XDR-TB will usually require treatment for around 18 months using a combination of different antibiotics. As these conditions are difficult to treat, you will be referred to a specialist TB clinic for treatment and monitoring.

Preventing the spread of infection

If you are diagnosed with pulmonary tuberculosis (TB), which affects the lungs, you will be contagious until you have received treatment for at least two to three weeks.

You will not need to be isolated during this time, but it is important to take some basic precautions to stop TB spreading to your family and friends. These precautions are:

  • Always cover your nose and mouth when coughing, sneezing or laughing. 
  • Carefully dispose of any used tissues in a sealed plastic bag. 
  • Open windows when possible to ensure a good supply of fresh air. 
  • Stay away from work, school or college until your TB treatment team advises you that it is safe to return. 
  • Do not sleep in the same room as other people because you could cough or sneeze in your sleep without realising it.


For most people, the Bacillus Calmette-Guérin (BCG) vaccination provides protection against TB. However, the BCG vaccine is not usually offered to people over 35 years of age. This is because there is little evidence that it provides protection for these people.

Before you have a vaccination, you will be given a Mantoux skin test (see Tuberculosis - diagnosis) to check whether you have latent TB. Latent TB is where you have been infected with the TB bacteria but do not have any symptoms. Vaccination is not recommended for people with latent TB because it will have no benefit and could cause unpleasant side effects.


The BCG vaccination is part of the childhood immunisation programme in Ireland.


The BCG vaccination is also recommended for older children who:

  • were not vaccinated against TB as a baby and who are at higher risk of contracting TB.
  • have not already been vaccinated and have been in close contact with someone who has pulmonary TB 
  • have not already been vaccinated and have come from a country with a high rate of TB, and
  • have no evidence of active or latent TB infection.

At-risk occupations

The BCG vaccination is recommended for people under 35 years of age whose occupation puts them at increased risk of exposure to TB. These people include:

  • laboratory staff who are in contact with clinical materials, such as blood, urine and tissue samples 
  • veterinary staff and other animal workers, such as abattoir workers, who work with animals that are susceptible to TB, such as cattle or monkeys 
  • prison staff who work directly with prisoners 
  • staff of care homes for the elderly 
  • staff of hostels for homeless people 
  • people who work in facilities for refugees and asylum seekers 
  • healthcare workers with an increased risk of exposure to TB 

See the Health A-Z topic about BCG vaccination - when it is needed for more information about who can and cannot be vaccinated.

Content provided by NHS Choices and adapted for Ireland by the Health A-Z.