They are stopped from multiplying by the immune system. Some bacteria may be 'walled off' in the scar tissue of the initial minor infection. However, not all the bacteria may be killed. The body's immune system at first stops the bacteria from multiplying (as above). Some people develop active TB months or years after a minor TB infection had been halted. Secondary (reactivated) infection causing active disease Newborn babies are also more at risk of active TB. For example, it is common in malnourished children in developing countries. However, it is more likely if you are already in poor health.
TB infection which progresses to active disease can occur in anybody who is infected with TB bacteria. Symptoms of active TB then develop about 6-8 weeks after first breathing in some bacteria. The TB bacteria multiply further and spread to other parts of the lung and body. In these people the immune system does not win the battle and halt the invading bacteria. Infection progressing into active TB disease - occurs in some casesĪctive TB disease with symptoms occurs in some people who breathe in some TB bacteria. This may be the only indication of a previous TB infection. A small scar on the lung may be seen on a chest X-ray. You are not usually aware that you have had this mild infection. There may be some mild symptoms for a short time, or no symptoms, and the infection is halted. The TB bacteria are killed or made inactive by the immune system. This stimulates your body defences (immune system) into action. The TB bacteria that you breathe in begin to multiply in the lung. Most people in good health who breathe in TB bacteria do not develop active TB disease. Minor infection with no symptoms - occurs in most cases
There are then three ways the infection may progress. If you breathe in some TB bacteria, they may multiply in your lung. The bacteria are carried in the air in tiny water droplets. TB bacteria are coughed or sneezed into the air by people with active TB disease. Age: babies, young children and the elderly are more susceptible to TB.Malnutrition: poor nutrition and lack of vitamin D are linked to TB.A poor immune system: for example, due to HIV infection, immune-suppressing treatment, or alcohol or drug dependency.
Environment and poverty: rates of TB are higher among homeless people, prisoners, in large cities and in more deprived areas.If you or your family come from a country where TB is common.Close contacts of a person who has active TB in the lungs (living in the same household, or spending a lot of time with that person).The risk is increased where one or more of the following apply: Rates of TB vary in different parts of the UK, with some London boroughs having very high rates.Īnyone can have TB. In England in 2015, just under 6,000 new cases were reported. It is thought this is due to several factors, including tackling poor housing and poverty and identifying and treating TB brought into the UK by immigrants. In the last four years, however, the rate has started to fall. More people travelling to areas in the world where TB is common.Immigration from areas where TB is common.This was probably due to a combination of factors. The number of people with active TB was at an all-time low in the UK in the early 1980s but the number of cases has since increased. AIDS (TB is common in people with AIDS).The main risk factors for TB in the developing world are: The death rate from TB is falling but it still causes about two million deaths per year worldwide. Tuberculosis (TB) is common in developing countries.
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