What is it?
Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis. TB may affect many body organs, but it primarily affects the lungs. It is spread through the air from person to person through lung secretions such as sputum (spit or phlegm) or aerosols released by coughing, sneezing, laughing, or breathing. Most of those who become infected with M. tuberculosis manage to confine the mycobacteria to a few cells in their body, where they stay alive in an inactive form. This inactive or latent TB infection does not make the patient sick or infectious and, in most cases, it does not progress to cause active tuberculosis.
However, some patients - especially those with damaged or compromised immune systems - may proceed directly from initial TB infection to active tuberculosis. And in another 10% of those with latent TB infection, the mycobacteria will later be reactivated and begin to multiply - leading to active progressive tuberculosis disease.
TB has been a leading cause of death for thousands of years. In the days before the discovery of antibiotics it was called consumption, and those who contracted it were put into long-term hospitals called sanatoriums for the rest of their lives. In Australia the National Notifiable Disease Surveillance System received 1,076 tuberculosis (TB) notifications in 2004 and the incidence of TB in Australia has remained stable since 1985 at approximately 5.4 cases per 100,000 population. High-incidence groups remain people born overseas and Indigenous Australians at 21.7 and 8.1 cases per 100,000 population, respectively. Worldwide TB is still the leading cause of death due to infection - killing more than 3 million people a year.
In developed countries the majority of recent cases are among those living in overcrowded or confined conditions such as prisons, nursing homes, and schools. The most vulnerable were those who had poor health care or had diseases and conditions that weakened their immune systems, such as: the homeless, alcoholics, intravenous drug users, those with HIV or AIDS, and those with chronic kidney or liver diseases. Often these new cases were multi-drug resistant (MDR), making them more difficult to treat.
In Australia the Australian Immunisation Handbook 8th Edition, 2003 immunisation program recommends BCG vaccines for:
- Aboriginal neonates (living in regions of high incidence)
- Neonates born to patients with leprosy or tuberculosis or with a family history of leprosy
- Children under 5 years who will be travelling to live in countries of high TB prevalence for longer than 3 months (WHO defines ‘high risk’ countries as those with an annual incidence of TB in excess of 100 per 100,000 population)
- Children and adolescents aged less than 16 years who continued to be exposed to an individual with acute pulmonary TB and where the child or adolescent cannot be place on isoniazid therapy or has completed isoniazid therapy.
State and Territory guidelines should be consulted for advice on vaccination of health care workers and children over the age of 5 years who will be travelling or living for extended periods in countries with a high prevalence of tuberculosis.
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