What is tuberculosis?
- Tuberculosis, often referred to as TB or consumption, is a curable infectious disease caused by the tubercle bacillus - also known as Mycobacterium tuberculosis or M. tuberculosis.
- 'Mycobacteria' means spore-like bacteria. TB bacilli have a thick waxy coat, are slow growing and can survive in the body for many years in a dormant or inactive state whereby people are infected but show no signs of TB disease. When the bacilli are awake and dividing people are said to have 'active TB'.
- TB can affect any part of the body but is most common in the lungs and lymph glands.
- Throughout the nineteenth and early twentieth century TB was rife in the cities of Europe and North America - London and New York were two of the worst affected cities.
- TB in the UK, and other industrialised nations, declined rapidly last century but never went away.
- Today, an estimated one third of the world's population - nearly two billion people - are infected. Nine million people a year develop the active disease and nearly two million die - one TB death every twenty seconds.
- TB was declared a global health emergency by the World Health Organization in 1993.
- Nearly all countries in the world are now affected by the global resurgence of TB caused primarily by increasing poverty and poor access to health services, migration and HIV.
Who catches tuberculosis?
- Anyone can catch TB.
- Although TB is increasing in the UK it remains quite rare (about 8000 new cases a year) and is predominantly confined to the major cities - about 40% of all cases are in London.
- In the UK, people who are at most risk of developing TB disease are 1) close contacts of an infectious case 2) those who have lived in places where TB is still common 3) those whose immune system is weakened by HIV or other medical conditions 4) people who experience chronic poor health through lifestyle factors such as homelessness, alcoholism and drug abuse 5) young children and very elderly people are more susceptible.
How is TB spread?
- People with active TB affecting the respiratory tract can infect others but not all people with respiratory TB are infectious. Other forms of TB e.g. lymph or bone are not infectious.
- The microscopic bacillus hitches a lift on an aerosol of tiny droplets of mucus and saliva produced when an infectious person talks, coughs or sneezes - others then inhale these droplets.
- In poorly ventilated areas the bacillus can remain suspended for several hours.
- Most people who get TB have had a prolonged exposure to an infectious person - usually someone in the same household.
- It is extremely rare for children with TB disease to be infectious - children get TB from adults with active respiratory TB.
What happens if you breathe in the TB bacilli?
- The majority of TB contacts experience nothing. Studies have demonstrated that only about 30% of healthy people closely exposed to TB will get infected and of those only 5%-10% will go on to develop TB disease. Young children exposed to TB are more likely to develop disease than healthy adults.
- What happens to the TB bacilli once in the lung is largely determined by your individual immune response - 70% of healthy TB contacts will completely eradicate the bacilli and show no signs of infection, the remainder will become infected and have a positive reaction to a skin test.
- For the 5%-10% who go on to develop TB disease the risk is greatest within the first 5 years following infection.
- A small number of people who become infected develop what is called primary disease, usually within 8 weeks of exposure. This can pass unnoticed and usually resolves without treatment leaving a small scar on the lung and surrounding lymph nodes that can be seen by chest X-ray.
- Children are more likely to develop primary disease than adults.
- If the immune system cannot kill or contain the bacilli they multiply resulting in damage to the surrounding tissues. TB bacilli can live in almost any part of the body so the effects are extremely varied depending on the site of disease.
What should be done after exposure to someone with tuberculosis?
- When someone is diagnosed with TB a team of specialist health professionals will make an assessment of the infection risk posed to others. If TB bacilli are found in the sputum of the TB sufferer then their contacts will be investigated to identify others who may have been infected.
- Contacts are defined as "close" meaning household and close family and "casual" meaning friends, work colleagues, schoolmates etc. Casual contacts are only investigated if the TB sufferer is assessed to be a serious infection risk.
- If you are identified as a contact at risk from TB then you will be routinely invited for screening.
- Screening will consist of a skin test to determine if your immune system recognises TB. The Mantoux test, which can be interpreted after three days, is safe and involves a small and virtually painless injection into the skin of the forearm.
- You may also be asked to have a chest X-ray when you have the skin test or if the skin test is strongly positive.
- In the UK a majority of people have had the BCG vaccine and so their skin tests will often be mildly positive. This does not mean that they have TB, it just means that their immune systems recognise TB.
- Because TB can develop some time after exposure contacts may be followed-up for up to one year with further appointments for screening and are advised to look out for suspicious symptoms.
- People who have a strongly positive skin test and / or evidence of TB infection found on chest X-ray, or who are unwell will be investigated further by a specialist doctor and may be treated with a course of anti-TB medication.
What are the symptoms of tuberculosis?
- Because TB can affect almost any part of the body the symptoms are extremely varied.
- The most common symptoms include:-
- Cough - lasting for more than two weeks and sometimes with blood streaked sputum
- Shortness of breath
- Loss of appetite and weight loss
- Fever and sweating - particularly at night
- Extreme fatigue and tiredness
How is tuberculosis treated?
- TB is now curable with antibiotics that must be taken for at least six months. Modern anti-TB drugs are extremely effective and in nearly all cases TB sufferers are not infectious and feel much better after the first two weeks of medication.
- Anti-TB drugs are always prescribed in combination to reduce the risk of the TB bacilli becoming resistant to one or more of them. For this reason patients will be started on three or four different drugs which should be taken daily or in certain situations can be taken three times a week on the advice of a specialist.
- A course of anti-TB drugs lasts for at least six months because the medicine is most effective against bacilli that are "awake" and growing. Six months of anti-TB medication has been demonstrated as the most effective duration to ensure that the dormant bacilli are also killed and then cannot wake up to cause TB disease in the future.
- It is vital that the medication is taken as prescribed. Taking anti-TB medication in the wrong dose, intermittently or for too short a time can result in the development of drug resistance making the disease much harder to treat and significantly increasing the sufferer's risk of long term complications or death.
- TB patients, and children in particular, will require support to help them remember to take their medication as prescribed and to deal with the physical and social consequences of the disease. TB is still highly stigmatised and patients can feel isolated and find it difficult to communicate their problems.
Can tuberculosis be prevented?
- The BCG immunisation increases a person's immunity to TB and protects against the most severe forms of disease such as TB meningitis.
- The schools' programme nationally has been replaced by targeted immunisation of children at increased risk of TB.
- The main recommendations for routine BCG vaccination of children are now: infants (aged 0 to 12 months) living in areas with a high incidence of TB (40/100,000 or greater), and any children with a parent or grandparent born in a high incidence country.
- Local arrangements exist to opportunistically identify, test and immunise those children at increased risk of TB who will no longer be offered BCG immunisation through the schools' program.
Tuberculosis and school attendance
TB can be very difficult to diagnose and can present in many different ways. The decision as to whether or not a school child or adult employee receiving treatment or being investigated for TB should attend school should be taken on the advice of local specialists. This will depend on the infection risk to others and, if none, whether they are well enough to attend.
If you want to know more about infection control in schools:
Guidance on infection control in schools and nurseries
Last reviewed: 21 March 2011