Tuberculosis
Introduction
Tuberculosis (TB) is an infection caused by a germ called the tubercle bacillus or
Mycobacterium tuberculosis. It can affect the lungs (pulmonary TB) or other parts of
the body, such as the lymph nodes (tuberculous adenitis or scrofula), the skin and
the bones. Tubercle bacilli can remain dormant for years before producing active
disease.
In most cases lung infection is well controlled by the immune system, and shows no
symptoms. Active lung disease occurs if the immune system becomes less effective.
A person may have had an infection with tuberculosis without being aware. This can
be discovered by a tuberculin skin test, the Heaf (or Mantoux) test. When positive, it
indicates that the person has a degree of natural immunity. People who test negative
do not have this immunity and are more susceptible to infection by TB.
Tuberculin-negative people may benefit from BCG inoculation. This uses a vaccine
made from a modified version of the TB germ. It reduces the risk of developing TB in
about 70% of those vaccinated for approximately 15 years.
Symptoms
Symptoms of pulmonary TB include fever, fatigue, loss of appetite and weight, night
sweats and persistent cough. Phlegm coughed up may be streaked with blood.
Tuberculous pleurisy (affecting the membranes around the lungs) leads to an
accumulation of fluid in the pleural cavity (the normally very small space between the
membranes) and partial collapse of the lung.
Causes
Pulmonary tuberculosis (which affects your lungs) is caught from an infectious
person by breathing in tubercle bacilli germs when they cough or sneeze. However,
tuberculosis is not easy to catch, and you need to be in close contact with an
infectious person for a prolonged period of time to be at risk.
The TB germ has a thick capsule, and can survive dry and usually hostile conditions
(although it is killed by UV light, for example, sunlight).
Risks
Tuberculosis is spread in a similar way to a common cold; by coughing and sneezing.
However, it is much more difficult to catch tuberculosis than it is to catch a cold,
because you need to spend a prolonged amount of time in close contact with an
infectious person to be at risk. Tuberculosis is unlikely to be spread through spitting
and cannot be spread by sharing objects.
Therefore, it is unlikely that you will catch tuberculosis unless you are living in the
same household as someone who is infectious. Even if this is the case, only about
10% of people who become infected with tuberculosis go on to develop the condition.
In most cases, the tubercle bacillus germs are destroyed or contained by your
immune system.
In addition to this, not everyone who has tuberculosis is infectious. Those who are
only remain infectious for about two weeks, if they are receiving the correct
treatment.
Contact tracing and screening for tuberculosis
If you have tuberculosis, your nurse will ask you to list the people you usually spend
most time with. These people will then be contacted and invited to be screened for
tuberculosis, to see whether or not they have been infected by the condition.
In most cases, your close contacts will not have been infected with tuberculosis and
no treatment will be necessary. However, it is important that your close contacts are
screened so that any cases of tuberculosis are identified and treated as early as
possible. This helps to prevent the condition from spreading further.
Screening for close contacts of those with tuberculosis may involve a blood test, a
chest X-ray, and a skin test (Mantoux test).
Treatment
Tuberculosis is treated with antituberculous drugs in combination, for at least six
months. However, you usually will start to feel better within two to four weeks of
starting medication.
Treatment normally consists of a combination of antibiotics. The standard treatment
involves Isoniazid and Rifampicin being given for at least six months. In addition,
Pyrazinamide and Ethambutol are also given for the first two months of treatment.
Rifabutin, Cycloserine, Capreomycin and Streptomycin can also be used in the
treatment of TB if drug resistance has been shown to be present.
It is vital to complete the course of drugs as directed. If this is not done, the bacteria
will not be completely gone and drug-resistant strains may develop.
Prevention
The old BCG vaccination programme, which was delivered through schools, was
replaced with an improved programme of targeted vaccination for people at highest
risk in September 2005.
Parents and health professionals will be able to find information about the changes
on the immunisation website or by calling NHS Direct on 0845 4647.
This factsheet has been produced using information provided by the NHS
Direct website. For more detailed information please visit
www.nhs.uk/conditions/tuberculosis