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Tuberculosis is the disease caused by infection with mycobacterium tuberculosis.
Tuberculosis is characterised by formation of tubercles and caseous necrosis in the tissues of any organ.
In man, the lung is the major seat of infection and the usual portal through which infection reaches other organs.
Patients with other species of mycobacterium are classed as atypical mycobacterial
infections. However NICE considers the M. tuberculosis complex as M. tuberculosis
or M. bovis or M. afrocami,.
NICE guideline provides guidance based on whether a patient has latent TB (evidence
of previous infection and TB is dormant) or have active TB (an ongoing TB related
illness such as pulmonary TB) (1):
- tuberculosis (TB) is a curable infectious disease caused by a type of bacterium
called Mycobacterium tuberculosis ('M. tuberculosis' or 'M.Tb'), or other
bacterium in the M. tuberculosis complex (that is, M. bovis or M. africanum)
- spread by droplets containing the bacteria being coughed out by someone
with infectious TB, and then being inhaled by other people
- initial infection clears in over 80% of people but, in a few cases, a defensive
barrier is built round the infection and the TB bacteria lie dormant
- called latent TB; the person is not ill and is not infectious
- if the immune system fails to build the defensive barrier, or the barrier
fails later, latent TB can spread in the lung (pulmonary TB) or develop
in the other parts of the body it has spread to (extrapulmonary TB). Only
a small proportion of people with latent TB will develop symptoms ('active
- many cases of TB can be prevented by public health measures and, when clinical
disease does occur, most people can be cured if treated properly. Taking medication
in the wrong dose or combination, irregularly or for too short a time can
lead to drug resistance
- drug-resistant strains of TB are much harder to treat and significantly
increase a person's risk of long-term complications or death. If left
untreated, 1 person with active pulmonary TB may infect as many as 10
to 15 people every year
- TB incidence in the UK has increased since the early 1990s, but has remained
relatively stable since 2005
- despite this, it remains high compared with many other western European
countries. Cases tend to cluster in urban areas where populations of at-risk
groups are high. These include areas with many people born in countries
with a high incidence of TB, areas with a high level of homelessness,
poor housing or poverty, and areas with high rates of problem drug use
Last reviewed 01/2018