Tuberculosis and Chest Service Department of Health - Tuberculosis (TB) - FAQ
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Frequently Asked Questions on TB

Q1.  What is tuberculosis?

Q2.  How is tuberculosis transmitted?

Q3.  What are the symptoms of tuberculosis?

Q4.  Why is it necessary for TB patients to attend chest clinics for supervised treatment?

Q5.  My family member is diagnosed with tuberculosis.  Should I disinfect all the things he had used before?

Q6.  Should TB patients be isolated during treatment to prevent transmission of the infection?

Q7.  Can TB patients travel by air?

Q8.  I have got a positive result on tuberculin skin test.  I am worried that I might have got tuberculosis?

Q9.  I am diagnosed as suffering from TB recently.  My wife is now pregnant, what should I do to prevent transmitting the disease to my wife?

Q10. My colleague is recently diagnosed as suffering from tuberculosis.  How should we clean the office?  How can we clean the air-conditioner?  Will the disease be transmitted through cleansing of the air-conditioner?

Q11. I suspect that I have tuberculosis, what should I do?

Q12. My child had BCG vaccination when he was a baby, do I need to bring him for vaccination again when he grows up?  What is the efficacy of the vaccination?

Q13. I am going to study in Canada .  My school's health centre requests the result of Mantoux test (tuberculin skin test) for tuberculosis.  Can you tell me what is the test and where can it be done?



A1.   Tuberculosis is an infectious disease caused by tubercle bacilli.  The bacteria usually invades the lung (90%), but may also invade other parts of the body such as lymph nodes, brain, kidneys, bones or joints.

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A2.   It is mainly transmitted through inhalation of airborne particles which contain tubercle bacilli.  The particles are generated by maneuvers such as coughing, sneezing, and singing by patients with tuberculosis.

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A3.  The symptoms of tuberculosis vary with different sites of the disease.  The most classical symptoms of pulmonary tuberculosis are:

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Ø        Persistent cough, usually with sputum, which is occasionally blood-stained

Ø        Anorexia (poor appetite)

Ø        Weight loss

Ø        Low grade fever, usually occurring in the afternoon

Ø        Sweating at night


A4.  This measure is called Directly Observed Therapy (DOT).  It means that patients need to take drugs under close supervision by health care workers.  It is recommended by the World Health Organization (WHO) as an effective method for ensuring drug adherence.  It helps to prevent patients from developing resistance to TB drugs due to irregular drug intake.  In addition, during DOT, health care workers can closely monitor patients for treatment side effects and give advice or take prompt actions when necessary.

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A5.  Tuberculosis spreads by airborne particles.  Clothing, beddings, kitchen utensils, and walls do not play significant role in the transmission of the germs.  Regular cleaning of the environment is a general hygienic practice.  Maintenance of good ventilation is beneficial to health.

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A6.  Once anti-TB treatment is started, the risk of spreading the infection is rapidly reduced.  For most TB patients, strict isolation is not necessary. The need of hospitalization or isolation may be considered on an individual basis.

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A7.  Persons with infectious tuberculosis should not travel by public air transportation until rendered non-infectious.  The degree of infectiousness will depend on the site of tuberculosis, extent of disease, presence of cavitary disease and duration of anti-TB treatment received.  When necessary, doctor’s advice should be sought.

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A8.  Positive tuberculin skin test may be due to previous BCG vaccination, TB infection, or infection with atypical mycobacteria.  If necessary, you may consult your doctor for clinical assessment and advice.  In fact, as TB is endemic in Hong Kong, many citizens have a positive tuberculin skin test due to past infection with TB.  However, the majority of those infected will remain healthy and disease-free.

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A9.  When an infectious TB patient coughs or sneezes, small droplets containing the bacteria are generated and spread in the air.  When a healthy person inhales the bacteria, he or she may or may not be infected.  Even if infected, only about one out of ten will develop the disease as a life-time risk.  The disease may develop weeks, months, years, or even decades after infection.  It would be advisable to maintain good personal hygiene, such as covering mouth when sneezing or coughing, as well as good indoor ventilation.  Moreover, adopting a healthy lifestyle with balanced diet, avoidance of smoking and alcohol, and adequate exercise, the bodily resistance can be enhanced and the chance of developing the disease can be reduced.  Generally speaking, the risk of spreading the infection is greatly reduced once treatment is started and patient takes the medication regularly.

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A10. Tuberculosis spreads mainly by air.  Furniture, tables, writing utensils, and walls do not play any significant role in the transmission of the bacilli. Routine cleaning of the environment should be done as general hygienic practice.  The dust filter of the air-conditioner should be cleaned as usual. The room should be kept well ventilated.

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A11. If you have any symptoms suggestive of tuberculosis, for example, persistent coughing for more than 3 weeks, loss of appetite, loss of body weight, low grade fever, or night sweating, you may attend (please bring along your identity card) any chest clinics during office hours for medical consultation.

        Further information may be obtained from the TB telephone hotline at (852) 2572 6024 by visiting the TB website:

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A12. BCG vaccination is given to nearly all newborn babies in Hong Kong for the protection against TB.  Its protective efficacy against TB is mainly in children and not in adults, and the protection is better seen against severe forms of the disease.  However, the protective efficacy is only partial and not 100%.  Repeated BCG vaccination cannot further enhance the protection against TB and is not recommended.

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A13. Mantoux test (tuberculin skin test) is a method for diagnosing latent TB infection. The test or other alternative test for latent TB infection is offered in some private health care facilities in Hong Kong. You may seek advice from your family doctor.

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