Information about Tuberculosis (TB)

Frequently Asked Questions 

Dr Anthony Byrne and Dr Yasmeen Al Hindawi are lung physicians and tuberculosis (TB) experts at St Vincent’s Hospital, Sydney.

Together, they have collated commonly asked questions to alleviate some of the anxiety, fear of the unknown and misconceptions about TB.

We strongly encourage you to read and view the TB educational resources provided by St Vincent’s Hospital, Sydney and NSW Health.


Why did I receive a letter advising me of recent tuberculosis exposure?

You have been identified as having been in the same workplace or clinical area, at the same time as an individual that had active tuberculosis in the lung.  The individual was not known to have tuberculosis at the time and may have been infectious. This means that there was the potential for you to have been exposed to the tuberculosis bacteria and you are at risk of active and latent tuberculosis.

Preventative therapy is available to significantly reduce the risk of developing active TB, which is a little like “post exposure prophylaxis”.


What is tuberculosis?

Active Tuberculosis, or TB, is an infectious disease that is caused by the bacteria Mycobacterium tuberculosis.

It can be spread from person to person via droplet transmission from the respiratory tract of an individual that is unwell with active tuberculosis (TB).

TB is not spread by common household items such cups, cutlery and phones.

TB most commonly affects the lungs but can infect almost any organ of the body.

TB is not as infectious as Influenza or COVID-19 and usually requires prolonged close contact with the source.

Tuberculosis bacteria grows very slowly so there is usually a delay from the time of exposure to the development of TB disease. This can be months, years or it may never develop at all.

Some people with active TB may only have mild symptoms. Symptoms may include:

  • A persistent cough for more than 3 weeks
  • Fevers
  • Night sweats
  • Unexplained weight loss
  • Loss of appetite

TB can be active or latent. Active TB is where the individual is infectious and has symptoms.

Latent TB is when the infection is dormant or “asleep” and is not infectious. 


What is the difference between latent TB and active TB?

In simple terms, active TB causes symptoms and can be seen under the microscope or grown from bodily fluids. Active TB causes changes to the body, seen on x-ray or CT. This form of TB is contagious.

Latent TB is inactive and not contagious. It cannot be seen under the microscope or grown from bodily fluids. A person with latent TB receives it from someone with active TB.

Latent TB does not cause any symptoms or health problems, but there is a small risk of reactivating or ‘waking up’ the bacteria to become active TB.

Reactivation of latent TB can sometimes be triggered by:

  • a social or physical stress - such as, hospitalization, illness and trauma or
  • medications – which lower the immune system, such as chemotherapy, immunosuppressants and steroids

Also, reactivation can sometimes happen for no obvious reason.


I thought TB did not exist in Australia?

The incidence of active TB is Australia is much lower than other countries. The incidence of active tuberculosis in Australia is approximately 6 per 100,000 people per year. However, worldwide, there were 10 million new cases of TB in 2019. There are still many cases of active tuberculosis diagnosed in Australia every year. 

In New South Wales last year, there were approximately 600 people diagnosed with active TB with around 5% of these treated at St Vincent’s Hospital.

Most cases of active TB in Australia are from people that have been exposed from living or travelling to overseas in high risk countries. This may be many years ago. TB can then “wake up” whilst living in Australia to cause active TB - so we do see cases of active tuberculosis that are “locally acquired”.


I have had the BCG vaccine many years ago, isn’t this a TB vaccine?

Unfortunately, the BCG vaccine does not provide adequate protection against TB disease for adults. In fact, most of the 10 million new cases of TB in 2019 occurred in countries where the BCG vaccine was routinely administered to children.

The BCG vaccine offers partial protection against developing active TB disease, mainly in young children. 

If you have had the BCG vaccine it is still possible to develop active TB. You will still need to have the QuantiFERON Gold, also known as IGRA blood test.

The QuantiFERON Gold blood test is the same as the IGRA blood test. At SVH we commonly refer to blood test as the IGRA test


What is my risk of “getting” active tuberculosis?

The chance of developing active tuberculosis is low.

Of those people that have latent tuberculosis (a positive IGRA) after their exposure, approximately 5-10% will develop active tuberculosis in their lifetime. The probability is highest in the two years after TB exposure.

The risk of active TB is also much higher in certain “at risk” populations such as:

  • Smokers
  • Diabetics
  • and people with
  • Chronic kidney disease
  • Reduced immunity and
  • HIV

Is screening for Healthcare Workers compulsory?


In the same way as measles, mumps and rubella require occupational screening, New South Wales occupational health and safety requirements include tuberculosis as one of the mandatory infections that requires health care workers to be screened.

This is even more important following possible exposure because active tuberculosis can affect the health of you, your family, and other people you have contact with.

As with other health conditions, it is important for you to know your TB status.  

If you are a healthcare worker it is recommended that you have ongoing TB screening.


What do I need to do now?

St Vincent’s Hospital has set up a special clinic to offer TB screening. You will be asked to have a blood test called an IGRA. There is no preparation, such as fasting, required for the IGRA blood test collection.

In addition to your letter that notifies you of your possible TB exposure, you will receive information sheets about tuberculosis and a “Tuberculosis Assessment Tool”. We ask that you compete your assessment tool, paying attention to the presence of any concerning symptoms such as an unexplained cough of more than 2 weeks, cough with blood or unexplained fever.

If you have any of these symptoms you will need a COVID-19 swab performed as well as a Chest X-ray prior to an appointment with the TB doctors.


How can I reduce my risk of developing tuberculosis?

If you are diagnosed with latent or inactive TB with a positive IGRA blood test, and take recommended preventative treatment, your risk of developing active TB will significantly reduce.

Studies have shown an approximate 70% risk reduction with preventative treatment, which would usually involve taking a daily antibiotic, called Rifampicin, for 4 months.


Is there any charge for these investigations and treatments?


All blood tests, medical imaging, medical appointments, and medications (if required) are provided to you at no cost.

Will I be able to take time off to complete these tests or investigations?

If you are a healthcare worker, your manager, or employer, will work with you to allow sufficient time for you to complete the required screening.

It is important that you attend all your scheduled appointments.


Will the IGRA, blood test tell me if I have tuberculosis?

The IGRA blood test diagnoses latent TB. It detects the presence of an immune response to the Mycobacterium tuberculosis antigen.

It cannot differentiate latent infection from active disease.

A positive IGRA test indicates tuberculosis infection from some time in the past and is not necessarily from a recent exposure. Importantly, the IGRA is not positive from a prior BCG vaccination.

How long does the IGRA blood test take to come back?

It takes approximately 3-7 days to receive the IGRA blood test result.


If I am pregnant can I still have the IGRA blood test?


There is no added risk to having the IGRA blood test if you are pregnant.

If the IGRA blood test is positive you would normally proceed to a Chest X-ray, however if you are pregnant you will see the TB doctor to discuss whether this is appropriate for you.


Am I still able to work whilst waiting for the IGRA blood test result?


Most people who have had exposure to a case of active tuberculosis will not become unwell with tuberculosis and therefore will not be infective to others.

However, if you are concerned that you are unwell and are experiencing symptoms, such as fever or cough, you should not work. First, you should undergo a COVID-19 test followed by a Chest X-ray and TB doctor review, regardless of the IGRA blood test result being negative or positive.


What if the IGRA blood test is positive?

If you have a positive IGRA blood test you will have a Chest X-ray followed by a TB doctor review. 

If you are well and your Chest X-ray is normal, the TB team will schedule your appointment.

However, if your Chest X-ray is abnormal or if you are immunosuppressed or have any symptoms of a cough, fever or weight loss you should notify the TB team.

Most people with a positive IGRA blood test will have latent tuberculosis infection, but some people may require further testing to ensure there are no early signs of active tuberculosis.

People with latent tuberculosis infection, that have had recent exposure to active TB, will usually be offered preventative treatment to reduce the risk of developing active TB in the future.

This is the reason for a medical review with a TB doctor. They will be able to talk to you, examine you and interpret all of the test results to diagnose your condition and explain the best management plan for you.


Do I need to do anything more if my IGRA blood test is negative?

Most people with a negative IGRA blood test will not require further testing.

You should remember that there is still the possibility of future TB exposure and as a health care worker you are at increased risk of TB exposure. There may be a need to repeat TB screening in the future.


What if I have had an IGRA blood test for tuberculosis before?

If you have had a positive IGRA test before you do not need to repeat it now. Please advise the TB team. You will need to have a Chest X-ray followed by TB doctor review.

If you have had a negative IGRA blood test before, you will need to have a repeat test now.

I had a positive tuberculin skin test or “Mantoux” for my health care worker screening tests. Do I still need to do the IGRA blood test?

If you had a positive tuberculin skin test ,also known as TST or Mantoux before, you do not need a IGRA blood test now. This result indicates you already have latent TB. Please advise the TB team. You will still need to have a Chest X-ray followed by a TB doctor review.

If you have had a negative tuberculin skin test, you will need to have a IGRA blood test now.


When will I be able to see a specialist to discuss my results?

If you have a positive IGRA blood test, the TB team will arrange a Chest X-ray followed by a TB doctor appointment as soon as possible.

If you have any symptoms that you are concerned about (fever, weight loss, cough) please advise the TB team so that your appointment with the TB doctor can be prioritised.

 If you have another health condition that may affect your immunity such as Diabetes, Chronic Kidney Disease, Human Immuno-Deficiency Virus, Silicosis or Systemic Lupus Erythematosus, please let the TB team know so that your appointment with the TB Physician can be prioritised


We recognise that this information may cause some concern for staff and patients.

To assist patients and staff with any concerns, St Vincent’s Hospital has implemented a designated TB hotline and email service. Email

In addition, St Vincent’s Healthcare Workers can access the Employee Assistance Program, also known as AccessEAP to support staff if they have any concerns. AcessEAP can be contacted on 1800 818 728


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