What is Tuberculosis?
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 those 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 to 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.
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 bacteria becoming resistant to those drugs. Drug-resistant TB may be more difficult to treat.