For much of modern history Tuberculosis (TB) was the archetype of a killer disease. In the 19th and early 20th centuries, the condition was a leading cause of death in Europe and North America, driven by urban crowding, poor living conditions, along with limited biomedical understanding. It was only in 1882, when Robert Koch identified ‘Mycobacterium tuberculosis’ as the causative agent, that science began to unravel the biological basis of the disease. In the decades that followed, public health interventions such as sanatoria, the Bacille Calmette-Guérin (BCG) vaccine, and eventually effective antibiotics transformed TB outcomes in high-income countries.
Yet, despite all these advances, tuberculosis cases never disappeared. It persists in contexts of poverty, inequality and weak health systems. In fact, while significant progress has been made in reducing TB deaths and cases in high-income countries, it remains one of the world’s deadliest infectious diseases till date.
In 1993, the World Health Organization declared TB a global health emergency, a recognition indicating that despite scientific tools to control it, TB continued to exact an enormous toll globally. Epidemiological data illustrates the persistence and expanse of the epidemic: an estimated 10.7 million people fell ill with TB in 2024, with Southeast Asia, the Western Pacific and Africa being regions reporting major cases.
A look at the numbers
India bears the world’s highest burden of tuberculosis cases, accounting for approximately 26 to 27 per cent of all global cases. As of 2024, the estimated TB incidence in the country is around 2.7 million cases. Despite gradual improvements and a decline in mortality to 21 deaths per lakh population, tuberculosis remains a major public health challenge, with an estimated two deaths occurring every three minutes.
Globally, about 1.23 million died from the disease, making TB the top infectious cause of death worldwide. Yet, the number of people officially diagnosed, represent only a portion of estimated cases. While estimated diagnoses increased in recent years, the gap between actual and detected cases persists; in 2024, only 78 per cent of TB cases were diagnosed and reported, leaving a substantial proportion undetected.
Analyses indicate that around 25 to 40 per cent of people who develop active TB may remain undiagnosed each year, particularly in high-burden countries with limited access to quality healthcare. Moreover, in India, which accounts for about 25 per cent of global TB cases, even with expanded diagnostic coverage, approximately 100,000 cases remain missing from official statistics, contributing to ongoing transmission. This enduring burden is in part driven by a stubborn disparity between actual disease and diagnosed cases.
The diagnostic gap in tuberculosis cases
One of the defining challenges in global TB control is the diagnostic gap: the difference between the number of people who develop active TB and those who are diagnosed. In 2024, about 8.3 million people were newly diagnosed and treated, representing roughly 78 per cent of estimated cases. That leaves over 20 per cent of cases undetected or unreported, a gap that carries serious implications.
The reasons for this diagnostic deficit are several. First, there are technical limitations in widely used diagnostic methods. Traditional smear microscopy, still common in many low and middle-income countries, has low sensitivity, especially in patients with low bacterial loads. In one Indian study, classic smear microscopy identified TB in only 4.3 per cent of samples, whereas more sensitive molecular methods detected it in 13.7 per cent. The persistence of suboptimal tools in resource-limited settings deepens the risk of missed diagnoses.
Research into the economic consequences in India illustrates that the failure to detect and treat TB escalates costs not just for the patient but for the broader healthcare system and society, as continued transmission generates additional cases and treatment demands. Moreover, TB disproportionately affects people in their most productive years. Loss of productivity due to illness and death translates into reduced economic output for communities and nations. Many households face catastrophic costs even when treatment is free, due to indirect costs such as transportation, lost wages, and caregiving.
Furthermore, undiagnosed TB perpetuates cycles of poverty and vulnerability. In communities with limited access to healthcare, this burden is compounded by stigma and lack of awareness, delaying diagnosis. Intersecting vulnerabilities highlight how TB operates not just as a medical condition but as a marker of deep societal inequities.
The Indian context
In the Indian context, there is a strong gender dimension to the burden of undiagnosed tuberculosis. Evidence suggests that more than one-third of tuberculosis cases in India go undiagnosed each year, with this gap being more pronounced among women. Social norms, stigma, gendered expectations often discourage women from seeking timely medical care, especially for symptoms such as chronic cough or weight loss, which are frequently overlooked. Limited autonomy and financial dependence reduce women’s access to diagnostic services, particularly in rural and low-income settings. As a result, many female patients remain invisible within the health system, leading to delayed treatment and continued transmission within households.
The way forward
This can be addressed in India by adopting a more people-centred and equity-driven approach to TB care. The focus needs to shift from waiting for patients to seek care to proactively reaching those who are most likely to be missed by the health system. This means strengthening community-based screening, improving early and affordable access to diagnostics, and ensuring that primary healthcare facilities are equipped to identify TB at the first point of contact.
Through its ‘Smile on Wheels’ programme, Smile Foundation delivers medical services directly to communities with limited access to hospitals, helping reduce the burden of preventable diseases on families. These efforts when combined with overall public health awareness can help reduce the number of undiagnosed cases and create a more effective TB response in the country.
