The World Health Organization (WHO) estimates that 304 000 people in South Africa fell ill with tuberculosis (TB) in 2021. Since only a fraction of people who breathe in TB bacteria will fall ill, the number of people who would have been exposed to the bug in 2021 would be much higher. Many of these people exposed to, or ill with TB would have been children or teenagers
Since TB is transmitted through the air, its transmission is thought to be particularly high in enclosed and overcrowded places where people breathe the same air - places like South Africa's notoriously overflowing classrooms.
The term scientists are increasingly using in this area is "shared air". Dr Graeme Hoddinott, Social Science Lead at the Desmond Tutu TB Centre and the Department of Paediatrics and Child Health at Stellenbosch University, explains that shared air simply means that the air that is breathed out by one person is breathed in again by another person.
"The more time we spend inside 'boxes' (for example, a room with closed windows or doors or no ventilation system), then the more times I will breathe in air that you have breathed out and vice versa," says Hoddinott.
He says the basic driver of TB transmission at school is people (learners and their teachers) spending long periods in a space where bugs have time to accumulate, such as in a classroom with the windows and doors closed.
Hoddinott says that if some of this shared air that is being breathed out has bugs in it, then odds are those bugs will be breathed in. He references a campaign run by advocacy group TB Proof that argued: "we do not share water that looks like it has bugs in it, so why should we share air with bugs in it?"
Measuring the TB in the air
The idea that there is TB circulating in the air in classrooms in high TB burden communities in South Africa is not only a deduction based on high TB rates and overcrowding in schools, but has increasingly been backed up by more direct research.
In one recent study, Dr Erick Bunyasi and colleagues from the South African Tuberculosis Vaccine Initiative (SATVI) measured both Carbon dioxide (CO2) levels and TB particles in the air in 72 classrooms in two high schools. There were over 2 200 learners in the 72 classes they monitored. Similar measurements were also taken at three outpatient TB clinics to provide a benchmark. CO2 levels are a good measure of shared air, since CO2 levels are higher in the air people breathe out than in the air they breathe in.
The study's findings were not reassuring.
"More than one-third of 72 high school classrooms were inadequately ventilated, and one-fifth of classrooms had evidence of airborne TB DNA detected," says Dr Angelique Luabeya, Chief Research Officer at SATVI and a co-author of the study.
She also stresses the study's finding that the average risk of inhaling one TB DNA copy was similar between clinics and classrooms. "This was concerning, as TB patients are more likely to attend the clinics. The fact that the clinic and the school have identical risks of exposure to TB DNA might suggest that there are undiagnosed TB cases among adolescents in classrooms who are exhaling TB bacilli at a comparable level of TB patients in the clinics," she says.
Luabeya is clear about the implications of such findings. In communities with high TB prevalence, she says, schools become potential sites of TB transmission.
What it means for learners
While the study by Bunyasi and colleagues identified only one case of active TB disease - likely an undercount since there was very little actual TB testing in the study - it leaves little doubt that there was TB particles in the air in several classrooms and that many learners would have inhaled TB bacteria while at school. Some of these learners may have TB infection, but not be ill with TB disease.
Dr Juli Switala, Senior Technical Specialist for Paediatric TB at the Aurum Institute, says individuals with TB infection don't feel sick, as the TB is alive but not multiplying or doing any damage, and they are also unlikely to be releasing TB bacteria into the air.
"This stable situation can go on for many years. The problem is that at some point later, it could be within weeks or years - the immune system may lose its control, allowing the TB bacteria an opportunity to multiply and start causing damage to the lungs and spread to other parts of the lung. This is what we call TB disease - and if it manages to reach the bloodstream, it can spread to any part of the body - including worst of all, the brain," says Switala.
"Even people with TB disease often don't feel very sick at all or take many months to notice that they are not well. Some may seek medical attention but because early TB disease is so mild and difficult to pick up, and [there is] no completely accurate test for TB - they are sometimes misdiagnosed," she says.
Late diagnosis is not only harmful to the health of individual learners who have TB disease, but it also increases the risk of further transmission. "A compounding factor," Hoddinott explains, "is that adolescents with TB are far too often not diagnosed, or even if diagnosed, they receive care that is sub-optimal. What this means is that a learner with TB might spend a number of days in their classroom breathing or coughing when they should instead have been diagnosed and started on TB treatment, which would rapidly reduce the number of bugs they would breathe out and thereby dramatically reduce the risk of transmission."
A further complication is that learners diagnosed with TB may face various forms of stigma. Hoddinott says it is important to help learners who do develop TB disease to have as minimal as possible disruption to their schooling. This includes letting them return to class as soon as it is safe to do so, accommodating them around exam periods, helping them to disclose or explain their absence to their friends or peers in a way that is safe, and ensuring that there is no lingering sense that the learner might still transmit TB.
"Many adolescents affected by TB also experience huge mental health co-morbidity (depression and anxiety)," he says. "And often, adolescents who develop TB disease come from contexts of hunger, poverty, etc. So, the headline is much more about showing care or love or respect for learners affected by TB and finding ways to mitigate the impact of TB on them and not about TB transmission in schools."
What to do about transmission in schools?
The most obvious solutions to the TB transmission problem are to reduce overcrowding and increase ventilation. While overcrowding in schools may not have any quick fixes, ventilation can be improved by opening windows and leaving doors open if feasible. Where new classrooms are built, they can be built with ventilation in mind. Having CO2 monitors in classrooms might also help in increasing teacher and learner awareness of shared air and related risks.
According to Hoddinott, reducing transmission in schools (as well as homes, clinics, taxis, workplaces, or churches for that matter) boils down to three things - "appropriate infection prevention control measures (for example ensuring good airflow by keeping windows open, mask-wearing if appropriate), getting people who have TB diagnosed quickly and offered treatment to reduce the time that they are infectious for (and get them better outcomes), and where appropriate, offering people who are exposed to TB bugs TB preventive therapy (for example, the children living in a home of an adult who has TB disease)."
He adds that the headline message around TB in schools should not be about transmission, but rather about how to equip learners, their educators and parents with the knowledge and ability to access TB care early. This, he says, includes a need for much greater collaboration between the departments of Health and Basic Education.
Luabeya also warns against a too-narrow focus on transmission in schools. "To improve the situation, it is essential to have interventions that decrease the TB prevalence in the communities where the children live [contact tracing of TB cases and active TB case-finding activities]," she says.
While regular TB symptom screening at schools is essential, she also points out that it will not detect sub-clinical TB. Sub-clinical TB is disease that has progressed beyond just TB infection, but has not yet resulted in TB symptoms.
Government's plans
The government department with primary responsibility for schools is the Department of Basic Education (DBE). Spotlight sent several questions to the department about their plans to address TB transmission in schools, but had received no response by time of publication.
However, according to the department's annual performance plan 2023/24, the department has allocated funds through the HIV and AIDS Life Skills Education Conditional Grant to support the implementation of its National Policy on HIV, STIs and TB for learners, teachers, and support staff in schools through health promotion programmes, including the HIV and AIDS Life Skills, Integrated School Health Programme (ISHP), HIV and TB, Comprehensive Sex Education, and Learner Pregnancy programmes. For the 2023/24 financial year the department allocated R241 million toward this.
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According to the plan, the allocation will be used to train teachers to implement Comprehensive Sexuality Education (CSE) and TB prevention programmes for learners to be able to protect themselves from HIV and TB. The department says it will prioritise schools located in areas with a high burden of HIV and TB infections. The grant is also used to capacitate school governing bodies and other school bodies to develop policy implementation plans focusing on keeping mainly young girls in school, ensuring that CSE and TB education is implemented for all learners in schools and that there is access to comprehensive sexual and reproductive health and TB services as well as implementation of TB services at secondary schools, the report states.
Among the outputs are to reach at least 45 districts "with the dissemination of the National Strategic Plan on HIV, TB and STIs 2023 - 2028 and the revised DBE national policy on HIV, STIs and TB". At least 5 600 schools is set to be reached through monitoring and support visits. The report doesn't contain much detail on how TB transmission will be mitigated in schools.
Yet, speaking at the South African TB Conference last year (2022) at the Department of Basic Education's satellite session themed "Prioritising Tuberculosis Response Among School-going Adolescents", Dr Reginah Mhaule, deputy minister of Basic Education, stressed the importance of building momentum in strengthening the integrated health programme for schools and adolescent-friendly healthcare.
"The department of basic education will be ensuring that classes are not overcrowded, and that there is proper ventilation," Mhaule said. "Part of what the department aims to do to control TB in schools is that screening is done at enrolment. We aim to raise TB knowledge in our schools and have a curriculum with more TB content."
