For two years, Xolani Mngomezulu from Indlovu Village in Mtubatuba, in northern KwaZulu-Natal, took at least eight pills a day and endured painful kanamycin injections after being diagnosed with multi-drug resistant (MDR) TB, a hard-to-treat form of the disease.
“Taking TB drugs was the hardest part. They made me nauseous and exhausted. But I survived a disease that has killed many, so I feel like a winner,” she says.
Despite her diagnosis in 2014, the 42-year-old mother-turned-TB activist didn’t have the usual symptoms such as coughing, chest pain, night sweats, or weight loss. This form of the disease is known as asymptomatic, or subclinical TB.
Mngomezulu was diagnosed after her brother fell ill and was diagnosed with MDR, following two weeks of persistent coughing and getting weak. Following his diagnosis, healthcare workers came to her home to screen everyone. “I was the only one who had contracted TB from him,” she recalls.
“But I didn’t feel sick at all and didn’t experience a single TB symptom. I remember when I was asked to cough up sputum [for the test], I couldn’t produce any because my chest was clear. Healthcare workers had to test my saliva, and that’s how MDR-TB was detected,” she tells Health-e News.
The mystery of asymptomatic TB
The World Health Organisation estimates that people like Mngomezulu make up about half of all TB cases. Because they don’t feel sick, they rarely visit clinics and are often only identified through national TB prevalence surveys.
There is a lot that researchers don’t understand about asymptomatic TB. For example, why do some people with active TB remain healthy and show no symptoms? A more urgent question is whether people with asymptomatic TB may be unknowingly spreading the disease.
Now, for the first time, scientists from the Africa Health Research Institute (AHRI) in South Africa and Padjadjaran University in Indonesia are setting out to answer this question in a new study, called Asymptomatic TB Transmission in Indonesia and South Africa (ATTIS). Researchers will recruit and screen about 90,000 people – 30,000 in South Africa and 60,000 in Indonesia – both ranked among the world’s top 30 TB-burdened countries.
TB remains a leading cause of death in South Africa, with about 270,000 people living with the disease in 2023, and 56,000 dying from the disease.
Testing children for TB
South African co-lead, Professor Limakatso Lebina, director of clinical trials at AHRI, says the local arm of the study will start in February and recruitment will be done over two years, mainly in the high-burdened rural uMfolozi area in King Cetshwayo District. In 2024, the district recorded about 2,503 TB cases, making up around 2% of South Africa’s total and ranking 25th across the country.
TB screening will be conducted among participants aged 15 and older. The process will include X-rays of the lungs, rapid GeneXpert testing of sputum, and other laboratory confirmation of infection. Children younger than 15 will get a blood test – Interferon-Gamma Release Assay, or IGRA – to check if they have previously been exposed to TB or had an infection.
Lebina explains that testing children is crucial and will give researchers clues as to whether people with asymptomatic TB can spread the disease to others. This is important because children usually catch TB soon after exposure, usually from someone close to them, such as a family member or caregiver. A child testing positive for TB is usually a sign that there is an infectious adult in their household or community.
Value of community testing
Beyond the question of infectiousness, Lebina says the study will help to determine whether large-scale community testing is worth expanding.
“In South Africa, we still have quite a large number of people with TB that are not on treatment,” says Lebina. “But it’s not a cheap exercise to go into the community and test everybody, even if they do not have symptoms. That is why we need to do this study to see if it is worth the investment, such as having more X-rays in the community, for instance.”
Subscribe to our newsletter
South Africa’s Targeted Universal TB Testing (TUTT) strategy has helped find more “missing TB patients” boosting testing by 17% to nearly 3 million people in 2024 after a COVID-19 decline. For 2025/2026 the department aims to ramp up its TB testing to 5 million people across the country.
Missing TB patients are those with TB but are either undiagnosed, unreported, or not reached by health systems. This group includes people with mild or asymptomatic TB, and those who are diagnosed but whose cases are not officially reported.
The TUTT strategy involves routinely offering TB tests to people living with HIV, household contacts of people with TB, and people who have had TB in the last two years – all groups considered to be at increased risk of TB.
The health department estimates that in 2022, there were 66,000 people with TB in the country who were either not diagnosed or treated. This group, which includes asymptomatic TB patients, is believed to be responsible for the ongoing TB transmission.
Global lessons for local impact
Getting answers to these questions will help the country and the WHO to develop policy recommendations and guide governments on whether they should invest in finding people with asymptomatic TB, and on which tools would be most effective for doing so.
Lebina says conducting a study of this scale in both South Africa and Indonesia – two TB-burdened countries with different risk factors, such as HIV in South Africa and malnutrition and smoking in Indonesia – will offer a global perspective and help guide policies on managing asymptomatic TB.
While Mngomezulu is relieved to have recovered from TB, she sometimes wonders if she might have unknowingly passed it on to others in her community.
“Research like this could be life-saving. With more knowledge, health workers will hopefully detect TB much earlier before it causes greater damage to the lungs,” she says. “Awareness will make it easier for people to go to the clinic and test even if they feel well.” – Health-e News
