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Tuberculosis (TB or TB disease) is a chronic infectious disease which may involve many organs of the body, but most often affects the lungs. Tuberculosis of the lung is called pulmonary tuberculosis.
Tuberculosis is a chronic infectious disease.
Tuberculosis is a bacterial illness caused by Mycobacterium tuberculosis. These bacteria are also referred to as TB bacilli (tuberculous bacilli).
Tuberculosis is caused by TB bacilli.
Tuberculosis is an infectious disease which results from the spread of TB bacilli from one person to another. TB bacilli are usually spread when a person with pulmonary tuberculosis talks, coughs, spits, laughs, shouts, sings or sneezes. This sends a spray of very small droplets from the person’s infected lungs into the air (i.e. airborne droplet spread). Live TB bacilli in these droplets then float in the air and may be breathed in by other people. If the inhaled TB bacilli reach the alveoli they cause a tuberculous infection of the lung.
TB bacilli are usually spread from adults with untreated pulmonary tuberculosis. Therefore, a child with tuberculosis almost always has been in close contact with an adult with pulmonary tuberculosis (the source of the TB bacilli). It is less common for a child to catch tuberculosis from another child as children usually do not cough up TB bacilli in large numbers. Therefore, adults with untreated tuberculosis are a danger to children in the family or household.
TB bacilli that infect children are usually spread from an adult with untreated pulmonary tuberculosis.
Children, especially those under five years of age, who are exposed to large numbers of TB bacilli.
Children who live in overcrowded, poorly ventilated homes or are exposed to crowded buses, taxis, schools, crèches and spaces where there are adults with untreated pulmonary tuberculosis. A child with tuberculosis often has an adult with untreated tuberculosis living in the same home. A mother with untreated pulmonary tuberculosis who is in close contact with her children is a great danger to her children.
Children in close, prolonged contact with adults who have untreated pulmonary tuberculosis are at greatest risk. Younger children are more likely to spend most of the day and night with an adult.
Children in poorly ventilated, overcrowded homes are at greatest risk of infection with TB bacilli.
No. Most children infected with TB bacilli do not develop tuberculosis (TB disease) because their immune system is able to control the infection and kill most of the TB bacilli. As a result, the natural immune response protects most children with TB infection from progressing to tuberculosis.
It is very important to understand that a child can only develop tuberculosis if the child is first infected with TB bacilli. Furthermore, TB infection does not always progress to tuberculosis (TB disease). Therefore TB infection without further progression is not the same as tuberculosis.
Fortunately most children infected with TB bacilli do not develop tuberculosis.
The progression of TB infection to tuberculosis is more common in children than in adults.
Children with a weak immune system are at the greatest risk. In these children, infection with TB bacilli may progress to tuberculosis because they have an inadequate immune system which is unable to control the infection. TB infection caused by large numbers of TB bacilli is also more likely to progress to tuberculosis.
Therefore, both TB infection and progress to tuberculosis are most common when a child with a weak immune system is exposed to large numbers of TB bacilli.
Children with weak immune systems are at greatest risk of tuberculosis.
Young children under five years, and especially if under two years, of age have immature (weak) immune systems which are unable to control severe infections. The immune system can further be weakened in:
HIV infection is the most important cause of a weakened immune system.
Children with HIV infection have the highest risk of developing tuberculosis.
Yes, infection with TB bacilli (Mycobacterium tuberculosis) is very common, and it is estimated that almost 50% of adult South Africans have been infected. Most infections take place during childhood.
TB infection is common and usually occurs during childhood.
Only about 10% of all people with TB infection progress to tuberculosis (TB disease) during their lifetime. Therefore, TB infection is far more common than tuberculosis.
The risk of TB infection progressing to tuberculosis is greater in young children than in older children or adults. In children infected under two years of age, the risk is as high as 50%.
About 10% of people with TB infection will develop tuberculosis.
The incidence is the number of people who develop tuberculosis per 100 000 of the population per year. This is a very useful measure as it allows the frequency of tuberculosis in different communities or countries to be compared. The incidence of a single community can also be compared from one year to the next.
While tuberculosis is uncommon in most developed countries, it is common in developing countries such as South Africa where the number of people with tuberculosis has increased rapidly in the last few years. The incidence of tuberculosis in South Africa was 834/100 000 in 2015. This is high when compared to developed countries like the United Kingdom where the incidence of tuberculosis in 2015 was 10/100 000.
In South Africa tuberculosis is particularly common in the Western Cape and KwaZulu-Natal. It is estimated that there are 400 new cases of tuberculosis per 100 000 children each year in the Western Cape. In any clinic children will make up approximately 15% of all the cases of tuberculosis.
TB is common in poor, disadvantaged communities where overcrowding, undernutrition and HIV infection are common. Tuberculosis is a disease of poverty. Tuberculosis spreads in any overcrowded living spaces, both at home and in the community. TB is often transmitted by a child’s family member, friend or close neighbour. However it may also be caught in a public space if there are many untreated patients in the community.
Tuberculosis is usually seen in poor communities.
Tuberculosis is a major cause of illness and death in many poor countries. These are preventable deaths, and the large number of patients with tuberculosis is a huge drain on healthcare resources.
Tuberculosis is an important cause of illness and death.
Tuberculous infection usually starts when TB bacilli are inhaled deep into the distant parts of the lungs, called alveoli. During the first six weeks of infection the immune system is unable to control the TB bacilli, which multiply rapidly in the alveoli where they cause a small, local area of inflammation. This is called primary tuberculosis. From the primary infection TB bacilli spread along the lymphatics to the local lymph nodes at the place where the main bronchi divide into branches (hilar nodes). The primary infection in the lung, together with the infected hilar lymph nodes, is called the primary complex. Parahilar and other mediastinal nodes may also be affected.
After six weeks the immune system usually becomes active and kills most of the TB bacilli in the lung and lymph nodes. As a result, the primary infection is asymptomatic in most children and does not cause clinical illness.
Therefore, the primary TB infection usually heals and does not spread any further, as the TB bacilli have been contained by the body’s natural immunity.
Inhaling TB bacilli into the lung may result in primary infection.
Sometimes the primary TB infection is not controlled by the immune system and the child now becomes ill with the signs and symptoms of pulmonary tuberculosis. This is a common form of tuberculosis in children.
With progression of the primary infection to pulmonary tuberculosis, the TB bacilli continue to multiply and an area of inflammation develops in the lung and lymph nodes in an attempt to prevent the TB bacilli from spreading any further. Often the centre of the inflamed area becomes soft as the tissues die. These dead cells (caseous material) can drain into the surrounding tissues.
There are a number of different ways that the primary TB infection can spread (progress) and lead to complications.
The primary TB infection may spread to cause pulmonary tuberculosis.
Pulmonary tuberculosis with enlarged hilar lymph nodes is the commonest form of tuberculosis in children.
Enlarged hilar lymph nodes may compress the airways causing wheezing.
The lungs are the commonest site of tuberculosis as TB infection is usually caused by inhaling TB bacilli.
While children usually have lymph node enlargement with few TB bacilli in the sputum, adolescents and adults usually have cavitary tuberculosis with destruction of lung tissue and large numbers of TB bacilli in their sputum.
Yes. This spread beyond the lungs is called extrapulmonary tuberculosis:
Tuberculous bacilli may spread from the lungs to other organs via the bloodstream or the lymphatics.
Although the lung is the commonest organ infected by TB bacilli, tuberculosis can involve any other organ of the body. Sometimes more than one organ is infected. The organs which are most commonly infected via the bloodstream in children are:
Tuberculosis involving multiple organs is referred to as disseminated tuberculosis. This follows spread of TB bacilli through the bloodstream to many organs. If disseminated tuberculosis includes widespread infection of both lungs, it is called miliary tuberculosis. This is a very serious illness with a high mortality rate unless diagnosed and treated early. It usually occurs in young children.
Disseminated tuberculosis is a serious illness with a high mortality rate.
Unlike pulmonary tuberculosis, tuberculosis of other organs is rarely infectious to other people.
Yes, extrapulmonary tuberculosis is far more common in children than in adults. Cervical lymph node enlargement is the commonest form of extrapulmonary tuberculosis in children.
Cervical lymph node enlargement is the commonest form of extrapulmonary tuberculosis in children.
Yes. Previous TB infection does not give complete immunity to further TB infections. A child with a healed primary infection can, months or years later, have another new primary infection when they are exposed to an infectious case of tuberculosis, especially if their immune system is weakened by severe malnutrition or HIV.
Therefore, pulmonary tuberculosis may be due to immediate spread from the original primary infection, reactivation (relapse) of an old primary infection which had not healed fully (latent tuberculous infection), or spread from a new primary infection (reinfection). In children, spread from the primary TB infection to cause tuberculosis is most common and usually occurs within two years of being infected (90% within one year of being infected).
Yes. During pregnancy TB bacilli in the mother can be spread via the bloodstream to the placenta. From here the TB bacilli may reach the fetus via the umbilical vessels or may infect the amniotic fluid and then be swallowed by the fetus. Infection during delivery is rare.
However, the spread of TB bacilli from a mother to her infant usually happens after delivery. The greatest risk is for an infectious mother to cough over her newborn infant. TB bacilli do not appear in the breast milk. Therefore breastfeeding is safe as long as the mother is on treatment and the infant receives prophylaxis.
A child of six years develops primary TB infection in her one lung. She remains clinically well however. When she is weighed by the school nurse, the mother is reassured that the child is healthy and thriving.
TB bacilli (Mycobacterium tuberculosis).
Because most children with a primary TB infection have no signs or symptoms of illness. Her immune system has controlled the TB infection.
Probably not, as most children are able to prevent the spread of TB bacilli from the primary infection.
Children with weak immune systems. These include young children, malnourished children and children with HIV infection.
Very common. Almost 50% of adult South Africans have had a primary TB infection at some time in their lives, most during childhood.
The risk of progression from TB infection to tuberculosis during a lifetime is about 10%. However the risk is higher in children and is as high as 50% in children under two years of age. Therefore TB infection is particularly dangerous in young children.
An 18-month-old child lives in an overcrowded home. During the day he is looked after by his grandfather who is unwell and has had a chronic cough for the past few months. The clinic nurse is worried as the child is malnourished and recently had measles.
Because the grandfather probably has undiagnosed pulmonary tuberculosis. The house is overcrowded and the child has prolonged contact with the grandfather. These factors all suggest that the child is being exposed to large numbers of TB bacilli.
Because the child has a weak immune system due to his young age, malnutrition and recent measles infection.
The child’s age and exposure to large numbers of TB bacilli will, therefore, increase his risk of both TB infection and progress to tuberculosis.
Yes, especially in poor, disadvantaged communities. Childhood tuberculosis makes up approximately 15% of all the cases at a TB clinic.
The primary infection in the lung may progress to tuberculous pneumonia. In older children and adults this may form a cavity. The grandfather probably has cavitary tuberculosis.
Yes. The primary TB infection in the lung is usually associated with enlarged hilar lymph nodes. Together they are called the primary complex. The enlarged hilar nodes can compress a large airway causing wheeze or stridor. Further enlargement of the lymph nodes may result in collapse or overinflation of a lobe.
The parents are very worried as their daughter has a lump in her neck which has been diagnosed as tuberculosis. Friends tell them that the diagnosis must be wrong as tuberculosis only affects the lungs.
No. Tuberculosis may affect most organs of the body. Tuberculosis outside the lungs is called extrapulmonary tuberculosis.
Tuberculosis of a lymph node (tuberculous lymphadenitis).
The meninges (TB meningitis), bones (TB osteitis), joints (TB arthritis) and abdominal organs (abdominal TB).
The spread of TB infection to many organs. This is a serious illness with a high mortality rate.
Usually not. However, extrapulmonary and pulmonary TB may occur in the same patient. Pulmonary tuberculosis is the most infectious form of the disease.
Tuberculosis can spread from mother to infant during pregnancy but this is uncommon. The greatest risk is when a mother with tuberculosis coughs onto her newborn infant.