Epidemiology of TB in India

Dr Giridhar R Babu

India has one fifth of the world’s burden of tuberculosis (TB) found and has a huge economic impact. According to recent estimates, TB caused India to lose an estimated $23.7 billion. In addition, 42 per cent of the total population in the country is classified as poor and hence TB can lead to catastrophic out-of-pocket expenditure. It is imperative to ensure overall oversight, management systems. Ensuring political will at all levels of government is also a key determinant of the initiative’s success. It has to be acknowledged that extreme times such as this require extreme actions.

India started its National Tuberculosis Programme (NTP) from 1962. The Revised National Tuberculosis Control Programme (RNTCP) adopted DOTS in 1997. RNTCP expanded in several phases to cover the entire population by 2006 and is the largest TB programme providing anti tubercular treatment for more than 1.5 million people annually. The programme has over 13,000 peripheral laboratories with smear microscopy services and has examined more than 36 million persons through sputum-smear microscopy and detected more than 7.5 million TB patients in the past five years. This mammoth programme screens nearly 25000 chest symptomatic persons per day for TB and detects, on an average, 3000 smear-positive TB cases and registers 4800 TB cases of all forms for treatment.

Out of the estimated 8.8 million new TB cases worldwide, 2.3 million occur in India. Over the last few years, India has been reporting about 1.5 million cases of TB annually and of them a little over 1.3 million are new (and relapse) cases. (Table-1) The gap in notification is about one million people with TB that either do not receive care or receive it under sub-optimal conditions with unknown treatment outcomes. This is a major challenge in the fight against TB in India. In addition, the gap between the smear positive TB cases diagnosed and those treated and notified is about 100,000 per year. It is important to include all the cases of tuberculosis and bring them into the ambit of national programme. Here, I describe the epidemiological steps of detection to identify opportunities of TB case detection and suggests steps to be taken to improve detection at each of these steps and provide a roadmap for implementation of the steps.

Epidemiological basis of TB Control

The estimated detection of new cases in India is falling short by at least one million per year. For a period of five years, this would result in a backlog of five million patients to be treated. In addition, approximately 100,000 patients are not diagnosed as TB even within the network of RNTCP hospitals. That means they add up 5,00,000 in the last five years. In effect, this means over 4.5 million people would be potentially transmitting the disease to the uninfected population in the last five years.

The rate at which the Indian programme is detecting new cases has remained stable. There are few possible reasons why this possibly might indicate detrimental effects. First, even if we were to assume TB transmission has really been reduced and only old cases are present in greater proportion; but this cannot explain the missing one million new cases per year. Second, there might be more deaths from TB that they don’t survive till diagnosis. Third, the proportion of people who are getting diagnosed for TB is same as proportion of TB cases being missed by the system. Realistic estimations of TB burden will provide the credible evidence for policy formulation and program implementation. To aid this, the Government of India can consider conducting nationwide population-based surveys of the prevalence of TB. These surveys would provide a direct measurement of the number of TB cases and their resistant forms, while repeat surveys conducted few years apart can allow direct measurement of trends in disease burden. There is abundant evidence that surveys are helpful in curbing TB burden in low and middle-income countries.

Additional challenge in poor detection of TB cases is compounded by rampant and irrational use of antibiotics to treat undiagnosed TB cases. This results in the patients to become resistant for second and third line of anti-tubercular drugs, generally reserved for those who do not respond to first line of treatment. This is one of the biggest contributor for burden of multi drug resistant (MDR) TB case.

According to the WHO Global Tuberculosis report of 2012, the estimated MDR TB cases among the notified cases are around 21000 patients per year. Extending the same proportion of MDR-TB to missed cases; India will have an additional 21000 cases annually. In total, with 42000 MDR TB cases annually, India should have had more than two lakh cases of MDR TB in the last five years. In contrast, the cases of MDR TB cases reported in India are only around 4000 cases.

Way ahead

The first pragmatic step is to enhance sputum specimen collection and transportation systems to full coverage by pro-actively establishing sputum collection and transportation from all public and private health facilities where TB symptomatics seek care, even if it costs significantly. It might be better to efficiently engage the services of NGOs, Anganwadi, ASHA, and the private sector laboratory specimen transport systems. This will ensure reduction in burden of primary TB and will greatly contribute towards prevention of drug resistance. Hence, the immediate priority is to bring the missed TB patients in the ambit of diagnosis and treatment. The challenge is exploring the attributes of finding around one million additional cases annually in terms of where they are missed, who is missing them and including all vulnerable sections as target beneficiaries for treatment.

The next immediate requirement is to address the need of innovative new diagnostics and improve their quality to not to miss the opportunities of treating the infected individuals due to false negative results. Keeping in line with this logic backed by epidemiological principles, the possible actions to be taken are therefore based on the epidemiology of tuberculosis.

The objective of RNTCP has so far been to detect smear positive TB cases by monitoring the number of TB symptomatic, which are tested with sputum smear microscopy. Though this indicator has been steadily increasing showing continued and successful effort for detecting TB cases. The Indian programme has done tremendous progress in improving the case notification rates. However, good case notification rates need not necessarily lead to early and rapid diagnosis of all persons with TB. Delays in detecting cases could in turn allow the spread of infection in the community before such cases are detected.

It is only realistic to think that there are several steps at which we miss TB diagnosis. Any delays before diagnosis can spread the TB infection in families, public places, and other overpopulated places. In India, this is expected since most of these delays are inherent to access issues with health centres. The next challenge is to resolve treatment failure after diagnosis of TB. The immediate precedence is to uphold the objectives of RNTCP, as highest scientific and epidemiological gains will come from prompt diagnosis and effective treatment. This can be followed through a combination of accurate diagnosis and actively seeking TB cases in high-risk and vulnerable populations. The next step would be to use newer technology driven diagnosis and detect greater proportion of cases for treatment.

There is a role for public health researchers and professionals. There should be greater evidence from the field in terms of how to integrate the existing private practitioners including the traditional healers into the ambit of TB case detection and treatment. It would be useful to generate evidence from the existing national health programs on motivating factors and enablers for private practitioners to report and treat TB cases as per national policy.