Tuberculosis (TB) is a bacterial infection. It is spread by inhaling tiny droplets of saliva from the coughs or sneezes of an infected person.
Mycobacterium tuberculosis is the bacteria responsible for TB. Mycobacterium tuberculosis are very slow moving, so a person may not experience any symptoms for many months, or even years, after becoming infected.
TB primarily affects the lungs (pulmonary TB). However, the infection is capable of spreading to many different parts of the body, such as the bones or nervous system. Typical symptoms of TB include a persistent cough, weight loss and night sweats.
Types of TB
There are three possibilities that can occur after becoming infected by TB. These are listed below.
- Your immune system kills the bacteria, and you experience no further symptoms. This is what happens in the majority of cases.
- Your immune system cannot kill the bacteria, but manages to build a defensive barrier around the infection. This means that you will not experience 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.
There is also the possibility that a latent TB infection could develop into an active TB infection at a later date, particularly if your immune system becomes weakened.
How common is TB?
Before antibiotics were introduced, TB used to be a major health problem in England. Nowadays the condition is much less common, although in recent years TB cases have been increasing, particularly among ethnic minority communities originating from places where TB is widespread.
There were 7,752 new cases of TB in England in 2007. Globally, TB remains a major public health problem. There were 9.2 million new cases of TB in 2007, and 1.7 million deaths resulting from the condition. It is also estimated that one-third of the world’s population is infected with latent TB.
Countries with high numbers of HIV cases also often have high numbers of TB cases. This is because HIV weakens a person’s immune system, which means that they are more likely to develop a TB infection.
Parts of the world that are known to have high rates of TB include:
- sub-Saharan Africa (all the African countries that are south of the Sahara desert),
- Asia, particularly south-east Asian countries, such as India, Pakistan, Indonesia and Bangladesh,
- Eastern Europe,
- Russia, and
- Central America.
Outlook
Left untreated, an active TB infection can be potentially fatal because it can damage the lungs to such an extent that a person becomes unable to breathe properly.
With treatment, a TB infection can usually be cured. Most people will need to take a long-term course of antibiotics, usually lasting for at least six months.
Vaccination
It is thought that between 70-80% of people who are given the Bacillus Calmette-Guérin (BCG) vaccine are protected against TB.
However, BCG vaccinations are not routinely given as part of the childhood immunisation schedule, unless a baby is thought to have an increased risk of coming into contact with TB compared to the general population.
For example, babies born in areas of inner-city London, where TB rates are higher than in the rest of the country, will probably be given the BCG vaccination.
Vaccinations may also be recommended for people who have an increased risk of developing a TB infection; for example, health workers, people who have recently arrived from countries with high levels of TB and people who have come into close contact with somebody infected with TB.
See the Prevention section, above, for more information about recommendations regarding BCG vaccinations.
