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The Disease
Tuberculosis (TB) is an infectious disease caused by the bacterium
Mycobacterium tuberculosis. TB causes more fatalities worldwide than any
other infectious disease. One third of the world’s population is infected
with TB, two-thirds of them in Asia. In Australia, the incidence is low.
While TB usually
infects the lungs (pulmonary TB), it can attack almost any human organ.
Airborne droplets resulting from an infected person coughing or sneezing
spread the disease. Although TB is harder to catch than the common cold,
it can result from extended exposure to an infected person, usually in a
confined space such as a classroom, hospital, train carriage or bus.
There have even been several cases of transmission on aircraft. TB can also
be transmitted through unpasteurised milk or milk products.
The symptoms of TB
generally include feeling sick or weak, weight loss, fever and night
sweats. With TB of the lungs, symptoms also include coughing, chest pain,
and coughing up blood. Other symptoms may occur, depending on which part
of the body is affected.
Risk for overseas travellers
There has been a marked increase in the incidence of TB in both developed
and developing countries in the last decade, resulting in a serious
public health problem - one that may impact on overseas travellers.
Travellers who anticipate possible prolonged close exposure to local
people (such as expatriates working in a hospital, classroom or some
other confined space; or budget travellers using buses, trains or local
aircraft extensively) especially in high-risk countries, should assess
the risk of TB.
Vaccination may be
recommended, especially for children. However, a tuberculin skin test may
also be appropriate for any travellers whose potential exposure is likely
to be significant. The skin test is used to determine if a person is
infected with the bacteria: not if they have TB disease. For the skin
test, a small amount of fluid called tuberculin is injected under the
skin in the lower part of the arm. Two or three days later, the arm is
inspected for a reaction. If the test is negative, the test should be
repeated on the traveller's return from overseas to determine if there
has been any exposure during travel. An alternate blood test for exposure
to TB, QuantiFERON-GOLD TB, is available through your medical
practitioner.
Because people with
human immunodeficiency virus (HIV) infection are more likely to have an
impaired response to the tuberculin skin test, travellers with HIV
infection should be advised to inform their travel health physician about
their HIV status. Except for travellers with impaired immunity,
travellers who already have a positive tuberculin reaction are unlikely
to be reinfected.
BCG vaccine
The Bacille Calmette-Guerin (BCG) vaccine is used in most developing
countries to reduce the severe consequences of TB in infants and
children. However, the BCG vaccine has variable efficacy in preventing
adult forms of TB and is not routinely recommended for use in Australia and for those travelling to developed countries. People who have been vaccinated
with BCG can be given a tuberculin skin test.
Treatment
TB is usually curable with antibiotics, however multidrug (MDR) and
extensively drug-resistant (XDR) forms have developed. Early detection is
important. If a returned traveller had a positive test, consideration
should be given to the possibility of drug resistance. Travellers who
suspect TB exposure should receive appropriate medical evaluation.
Drug therapy of 6
to 12 months can cure TB disease. The drugs should be taken exactly as
prescribed: stopping too soon or taking drugs incorrectly may result in
surviving germs becoming resistant to those drugs. Drug-resistant TB may
be more difficult to treat.
More information on this and related health risks will be
available during your Travelvax consultation. Call 1300 360 164 for the
location of your nearest clinic.
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