Tuberculosis, dramatically described in Victorian times as "consumption of the lungs," is proving to be as serious a public health problem at the start of the 21st century as it was at the start of the 20th, despite the fact that the cause is known & effective drugs available.
Approximately one-fifth of the world's population is infected but up to 97% live in very poor countries or under poor conditions in the more developed countries.
The disease can affect all parts & organs of the body but it is when the lungs are involved that the infected person becomes most infectious to others. It results from invasion of the body by a specific germ called Mycobacterium tuberculosis. Illness will occur from repeated or overwhelming invasions of the germ, or when the body's immune defenses are lowered by other diseases or malnutrition. In a society with no poverty, overcrowding, poor hygiene, undernutrition, alcoholism, chronic hepatitis or HIV infection the Mycobacterium would be relatively innocuous.
Prolonged contact with an infectious person is generally needed for the germ to be transmitted & even then only about 10% of people infected will go on to develop the disease depending on their state of health & living conditions. The high prevalence throughout the world thus implies that tuberculosis is far more a social problem than a medical one.
Since prolonged contact is needed air travel is not regarded as hazardous. Nevertheless the potential for infection exists & Guidelines issued by the World Health Organisation have been accepted by all major international carriers.
A short-term visit to an area with a high incidence of Tuberculosis should pose no problem but people with low immunity either from disease (HIV infection; poorly controlled diabetes; chronic liver disease; leukaemia, lymphoma) or treatment (chemotherapy for cancer) should exercise care.
Prolonged stay is another matter. Healthy, well-nourished individuals should not have any concerns although health care workers may be at high risk & will need expert advice. Infants & young children, however, are at greater risk than adults & BCG inoculation is recommended.
There is no true vaccine against tuberculosis but inoculation with an extract of a related bacillus, known as BCG, will provide protection against the serious forms of the disease which can occur in infants & young children. It's value in protecting older individuals is not proven & in the USA it is not used at all. Other authorities including the World Health Organisation disagree with this policy. In Australia BCG is not given as a routine but State health authorities will give it to high risk groups, & it may be offered to adolescents as part of the School Health Service or to students on exchange schemes although this is subject to review.
BCG vaccine cannot be given within one month of receiving a live virus vaccine (yellow fever; mumps/measles/rubella). A small ulcer develops at the site of inoculation & rarely a generalised illness with lymph gland enlargement & fever may develop which can be successfully treated. It takes up to three months for BCG vaccination to provide protection.
MANTOUX TEST or TST (tuberculin skin test)
This is a test using a purified derivative of the tuberculosis bacillus injected into the skin, usually of the forearm. A sensitivity reaction to this extract will occur within 72 hours if there has been a previous infection, a current infection, previous BCG inoculation or because there is a natural immunity. The reaction is measured in millimetres & recorded. Interpretation of the result is not straightforward & needs medical judgement. The test is used to decide if a person, usually an older child or adolescent, should be sent to have a BCG inoculation. In addition, because the Mantoux test is frequently used to help with the diagnosis if there is suspicion that tuberculosis may have developed after a term of residence in a high risk country, it is very useful to record the result of a routine "baseline" test. Individuals who have a strong positive baseline reaction would be referred to the State tuberculosis authority for assessment.
Quantiferon-TB Gold tests
This is a new blood test that identify people infected with the TB germ, but not sick. It can distinguish between TB infection & the BCG vaccine ( the Mantoux test cannot), & is useful for identifyinh a possible exposure by testing before & after. It is less accurate in children, & is not a good predicter for active disease.
For low-risk healthy travellers, this has largely replaced the role of TST in checking for exposure & latent disease.