Tuberculosis (TB) is primarily a lung infection caused by the bacterium Mycobacterium tuberculosis, which can penetrate lung tissue causing inflammation and the development of tubercles (encapsulated bacterial cells) . These tubercles may rupture allowing the infection to spread to the surrounding tissue, the circulatory and lymphatic systems, and consequently to other parts of the body. They may also lie dormant, reactivating years later. Few symptoms are specific to the disease but persistence in symptoms is a feature in all forms of TB . Of concern are coughs lasting longer than 2-3 weeks and/or blood-stained sputum.
It is almost certain that Indigenous people did not suffer from tuberculosis prior to 1788 . There was evidence of a high prevalence of TB among the first Europeans to arrive in Australia, however, and it is likely that the disease was soon transmitted to Indigenous peoples. There is little evidence of TB having a major impact on Indigenous people until around the middle of the 19th century, after which time it became the leading cause of death for those living in the more settled parts of the country . For Indigenous people living in more remote parts of Australia, TB did not have a major impact until much later .
By the mid 20th century, the disease had spread to Indigenous communities in all parts of the country, but its impact was still somewhat variable . The rate in the non-Indigenous population declined from the mid 20th century, partly due to a highly successful national TB campaign (1948-1976) . The persisting impact of TB on Indigenous people has been attributed to the poor living conditions and malnutrition experienced by Indigenous people, compounded by chronic chest diseases and alcohol use   .
TB is considered to be well under control in Australia with one of the lowest rates in the world. Notifications of TB among Aboriginal and Torres Strait Islander peoples have declined slightly, but they still remain much higher than those in the Australian born population .
There were 1,142 new cases of TB notified in 2006, but 969 (85%) of these were for people born outside Australia . Of the 173 new cases involving people born in Australia, 33 (19%) were identified as Indigenous and 140 (81%) as non-Indigenous. The number of new cases of TB among Indigenous people in 2006 was slightly more than the number in 2005 (27), but less than those in previous years    .
In view of the relatively small numbers of cases and the year-to-year variations in numbers, the following comparison of TB incidence among Indigenous and non-Indigenous Australian-born people considers new cases for the five-year period, 2002-2006. In that period, there were 174 new cases of TB notified among Indigenous people and 711 among non-Indigenous Australian-born people     . Almost one-half of the new cases among Indigenous people were reported by the Northern Territory (83 cases) and around one-quarter by Queensland (45 cases) (Table 1). The Australia-wide crude incidence rate of 7.2 cases per 100,000 population for Indigenous people was almost 10 times the rate of 0.7 per 100,000 for non-Indigenous people. The crude incidence rate was highest for the NT (28 cases per 100,000 population).
This comparison underestimates the true difference between Indigenous and non-Indigenous people because of differences in the age structures of the Indigenous and non-Indigenous populations - after adjusting for these differences, the incidence rate for Indigenous people was 14 times that of non-Indigenous people (Table 2). The incidence of TB is higher for Indigenous people than for non-Indigenous people across all age groups, with rate ratios being highest for the 45-54 years and 55-64 years age groups.
|Source: Derived from      |
|Age group||Indigenous||Non-Indigenous||Rate ratio|
|Source: Derived from      |
The most common risk factor for TB infection in Australia recently has been household or other close contact with an infected person . Other risk factors include: overcrowding; malnutrition; unemployment and homelessness; diabetes mellitus; low body weight; smoking; alcohol abuse and advanced renal disease  . A recently emerged risk factor for tuberculosis is HIV infection .
The national strategic plan for TB control in Australia beyond 2000 aims to minimise the burden and human impact of TB and prevent transmission through early detection and treatment . The present low incidence of tuberculosis among non-Indigenous Australian-born people confirms the disease can be largely prevented and certainly controlled. The low levels can be attributed to the high socioeconomic circumstances enjoyed by most Australians, and the success of TB surveillance and control programs . An increasing concern, however, is the worldwide emergence of multi drug resistant disease .
The main focus of TB control efforts in Australia are: active and passive case-finding; prompt and effective treatment of persons with active TB: and timely surveillance and reporting of disease incidence, drug resistance and treatment outcomes . These components are undoubtedly crucial.
Achievement of the National Strategic Plan’s goal of reducing ‘the incidence of TB in the Indigenous Australian population to that of the Australian-born non-Indigenous population’, however, also demands that much more attention be given to the underlying factors contributing to the current fourteen-fold difference in incidence. Addressing these factors, largely outside the direct control of the health system, will be another test of Australia’s commitment to 'closing the gap' between the heath and social circumstances of Indigenous and other Australians.