TB is one of the oldest known infectious diseases. According to the World Health Organization, each year more than one million people die from TB worldwide, and it has retaken from Covid-19 the mantle of the leading infectious cause of death.

TB predominantly affects the socioeconomically disadvantaged, highlighting iniquitous distributions of wealth and health. Even in high-income, low-burden countries, TB typically occurs among socially and economically vulnerable populations.

World Tuberculosis (TB) Day is observed annually on 24 March. The theme for 2024 – “Yes! We can end TB!” – emphasises the importance of individual and collective action to end the global TB epidemic. TB is commonly considered an acute illness that is diagnosable, treatable and curable.

However, in recent years researchers have begun to question the meaning of living with TB. A central tenet of our chapter published in The Routledge Handbook of Anthropology and Global Health earlier this month is rooted in this emerging argument: That many people who are affected by TB experience its impacts over a much longer period, from episodic to even lifelong, requiring TB programmes – including TB clinicians, nurses and counsellors – to shift their approach to TB diagnosis, prevention, treatment and care.

We connect these arguments through three points. First, we acknowledge that TB exists along a spectrum. Almost a quarter of the global population is understood to have latent TB or TB infection. That is, they are infected with the TB bacteria, but not infectious or currently experiencing any of the symptoms related with active TB disease.

Next on the spectrum is a group of people who have incipient or subclinical TB, in whom TB would be detected using TB-specific tests, but might complain of only mild, nonspecific symptoms. This group substantially contributes to TB transmission.

People who develop TB commonly have other diseases which increase their risk of worse health outcomes because of overlapping negative social, physiological or psychological effects.

Then there is the group of individuals who have active TB or TB disease; they are infectious and experience symptoms.

These many ways of living with TB – the undiagnosed and often untreated and the diagnosed and treated – are increasingly joined by another group of people, former patients, or TB survivors.

These are people who have been cured of TB or reached “treatment completion” and are understood to have escaped TB. However, even after cure or completing treatment, TB survivors often experience long-lasting physiological and psychosocial challenges.

Not only are they at greater risk of experiencing another TB episode, but they are also at greater risk of developing chronic lung disease(s), persistent respiratory impairment and other TB-related disabilities. Finally, they have a higher mortality rate than people who have never had TB.

Second, our chapter highlights how TB increasingly occurs alongside, and is aggravated by, a plethora of other infectious and chronic diseases. TB is typically not the only illness affecting those who develop it. They commonly have other diseases, or comorbidities. These diseases increase their risk of worse health outcomes because of overlapping negative social, physiological or psychological effects.

Additionally, people comorbidly affected by TB must navigate the sometimes complex demands of the health system and care. Among these co-occurring conditions, HIV is the most notable.

TB is the leading cause of death in people living with HIV (PLHIV). They have poorer success on TB treatment, even lower among people infected with drug-resistant forms of TB. They also have an increased risk of recurrent TB.

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Although antiretroviral therapy (ART) has extended the life expectancy of PLHIV, over time they become prone to developing chronic diseases like diabetes. People with diabetes face poorer treatment outcomes for TB, are at increased risk of developing resistance to first-line TB medications and are at an even greater risk of recurrent TB than those without diabetes.

Third, TB, and many of these co-occurring conditions, share social determinants of health that render entire populations susceptible to enduring debilities.

When we consider how TB predominantly occurs in places of disparate social and economic opportunity alongside other diseases… we begin to see it as chronic.

In South Africa, and other resource-limited countries, poverty, malnourishment and a struggling health system continually place people at risk for TB. Forty-nine percent of households in which one (or more people) had TB experienced “catastrophic” costs – defined as costs exceeding more than 20% of their household income.

Even in places like South Africa where TB treatment is free through the public health system, households affected by TB incur indirect costs related to treatment and care.

For example, they may have to pay for specialist consultation fees or tests, transport to and from numerous health facilities while seeking a diagnosis or retrieving treatment, and even nutritional supplements. These costs are particularly burdensome for people with multidrug-resistant TB. Additionally, people infected with TB might lose their jobs or source of income.

In pulling these three strings of argument together, we join others who have begun to challenge ideas about which diseases are considered chronic over the past decade.

For example, today most public health specialists consider HIV a chronic, manageable disease. Yet many PLHIV in high-burden, low-resource settings struggle to get the necessary care and socioeconomic support to achieve relatively good health. Temporary lapses in adherence to ART are common and can cause fluctuations in immunity and even vulnerability to opportunistic infections, like TB.

At these moments, PLHIV experience their otherwise “chronic disease” as an acute assault on their lives. Another way in which people have begun to challenge notions of chronic and acute disease, is through consideration of how global shifts in socioeconomic conditions have increased, and to some degree necessitated, local access to foods that quicken “diseases of lifestyle” – like type 2 diabetes.

People, especially those living in low-resource settings, have limited choices over the foods they can afford, placing them at increased risk of lifestyle diseases.

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When we consider how TB predominantly occurs in places of disparate social and economic opportunity alongside other diseases, time and again, we begin to see it as chronic. The TB response must shift from an “infectious disease” model to addressing the chronic characteristics of TB.

It is here that the risk of TB infection, reinfection and recurrence appears perpetual, and where health systems and social support structures fail to provide people succour. Thinking of TB as a chronic condition – if not disease – provides the opportunity to highlight the long-term, potentially debilitating impacts it has on many people with limited socioeconomic resources.

As others have begun to suggest, we believe the TB care cascade could adopt a more cyclical and rehabilitative approach to help reduce the impact of TB on people’s lives.

This also means addressing the underlying social determinants of health that contribute to increased risk of exposure to TB by developing a sustained response that carries affected people through the continuum of TB care, including prevention and care of TB recurrence and rehabilitative care for people who experience long-term impacts of TB. DM

Dr Dillon Wademan is a principal research officer at the Desmond Tutu TB Centre at Stellenbosch University.

Dr Amrita Daftary is a social and behavioural global health researcher at the School of Global Health at York University.

This article is based, in part, on their chapter, “The neglected chronicity of TB”, in The Routledge Handbook of Anthropology and Global Health (Routledge, 2024).