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). It is spread by droplets containing the bacteria being coughed out by someone with infectious TB, and then being inhaled by other people.
The 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. This is 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 TB').
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.
The NHS and Public Health England, as well as a local authority public health teams and many third sector organisations, have been working to reduce the harm caused by TB to many individuals and communities. TB is a notifiable disease, meaning that clinicians have a statutory duty to notify local authorities or a local Public Health England centre of suspected cases, and efforts have been made to strengthen services and ensure clear lines of accountability and responsibility. However, a stronger approach to TB control is now needed to build on this work. Indicators of TB incidence and TB treatment outcomes have been included in the Public Health Outcomes Framework. In addition, Public Health England and NHS England have designed a collaborative tuberculosis strategy for England that brings together best practice in clinical care, social support and public health. Agencies at all levels – including national and local government, clinical commissioning groups and third sector partners – are committed to working in partnership to decrease the incidence of TB, fight the spread of drug‑resistant forms of the disease, reduce current health inequality and, ultimately, eliminate TB as a public health problem in England.
You can also see this guideline in the NICE pathway on tuberculosis.