I have worked for several decades as a primary care doctor in the South African public sector. Over the years, a number of women have contacted me, with a concern expressed in almost identical words, saying something like: “Dr Giddy, Florence my domestic worker was diagnosed with TB last week.” The anxious and fearful voice continues: “We have children, and I am really worried that someone in our family may catch TB, or have caught TB already from Florence.” It falters and then asks: “What must we do now? Can you test all of us for TB?”

I used to start my little mini lecture in response with something like: “I understand your concern, but in South Africa we all live in a sea of TB.” I would go on to say that TB was extremely common and so we were all at risk and that you could get it from anyone, anywhere – in a shop, or the post office or bank. Therefore, having someone close to you, like Florence, diagnosed with TB was not a particular risk.

I would also say something about the immune system and that if we had a good diet, and were generally well, then our immune system would be strong, and despite breathing in TB bacteria, our immune system would protect us and we would be very unlikely to get sick from TB.

I would tell Mrs Worried that it was very difficult to diagnose TB early, so it was not worth testing for it, since it was unlikely to show up in a chest X-ray which is what she was wanting. It would be better to wait until a person had some definite signs of TB, like coughing, fever or losing weight, because then it would be easier to diagnose, and that it would be better to do a sputum test – coughed-up phlegm sent to the laboratory – rather than a chest X-ray.

The final thing I would say was that the only way to prevent TB was to open windows to let in lots of fresh air.

I would emphasise to Mrs Worried that once Florence had been taking TB treatment for two weeks she was no longer infectious and could continue working if she was well enough. I would also tell her that she needed to show care and concern towards Florence, and support her to finish her full course of TB treatment.

In the past few years I have realised that I was wrong about some of the things I said to the various worried employers who contacted me. Not wrong about everything, just some of the facts that I communicated so confidently at that time. There have been some significant changes in TB knowledge and related to this new evidence, there are new TB policies with major implications for everyone who lives in South Africa.

What was correct about what I previously said?

TB really is very common in South Africa. It is estimated that about 300,000 people develop TB every year and it is the most common single cause of death from an infectious disease, responsible for roughly 54,000 deaths annually in the country.

Our immune system does protect us from developing TB as well as many other diseases. We know that certain choices we make can boost the immune system, such as a healthy diet, not smoking or drinking too much alcohol, getting enough sleep, and managing stress positively. If you are living with HIV, antiretroviral therapy will protect your immune system and dramatically reduce the risk of falling ill with TB.

Tuberculosis is caused by bacteria and spreads through air and can infect anyone. (Infographic: World Health Organization)

It is also still generally thought that two weeks – although some studies have suggested it may be shorter – after starting effective TB medication a person is no longer infectious and therefore not at risk of transmitting TB to those around them.

And it remains true that people with TB need care and support to complete their course of TB medication and that improving ventilation does help to reduce the risk of TB transmission, which is particularly important in crowded settings.

What then has changed?

A new National TB policy published in 2023 recommends that all close contacts of people with TB disease are tested with a sputum test or chest X-ray. These close contacts are at higher risk of getting TB, particularly children under five years. They are people who share a household, share transport regularly, work closely together, sit close together at school, and so on.

We also now know that people can have TB disease that is infectious without having the typical symptoms such as cough, loss of weight, sweating at night, tiredness and lack of energy. The First National TB Prevalence Survey showed that 57.8% of people found to have TB based on sputum tests or chest X-rays had no TB symptoms.

Recent national TB guidelines recommend that people who are close contacts of a person diagnosed with TB should be offered medicines to prevent TB, after TB disease is ruled out. There are various options for this – either daily tablets for six months or once a week for 12 weeks (a total of 12 doses). What has changed here is that many more people than before are now eligible for these medicines that prevent TB. The much shorter 12-dose course is also new.

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So, now what I will say when a Mrs Worried phones me is:

“Thank you for your question about TB infection risk. You are correct to be concerned about the risk of getting TB. If Florence works as a domestic worker in your home and has had regular interaction with you and your family, then you are all close contacts and therefore at risk of TB disease. You will need to do a test to exclude TB – usually phlegm is sent to the laboratory, but the test could also be a chest X-ray. If you or other family members test negative for TB, then you should take TB preventive medication to protect yourself from getting sick with TB.  These services are all offered at your local clinic and will not cost you anything. It’s important to remember that anyone can get TB. Please support Florence to continue her TB treatment, and note that she is not infectious any longer if she has been on effective treatment for at least two weeks.” DM

Giddy is a medical doctor and member of TB Proof.

This article was published by Spotlight – health journalism in the public interest. Sign up to the Spotlight newsletter.