World Tuberculosis Day: A Closer Look at the Challenges in Eradicating TB

World Tuberculosis Day is commemorated by the WHO on 24 March each year, with the aim of raising awareness about the disease. The date is not accidental; 24 March 1882, the German microbiologist and future recipient of the Nobel Prize, Robert Koch, announced his discovery that tuberculosis (TB) was caused by the bacterium Mycobacterium tuberculosis.

Most people in high-income countries think of TB as an infectious disease of the past – maybe familiar with the high mortality rate in Europe in the 19^th and early 20^th centuries. But in reality, TB is the world’s leading cause of death from infectious disease, and was only briefly eclipsed by COVID-19 during the pandemic. In 2021, approximately 10.6 million people worldwide were ill with TB, and 1.6 million people died from the disease, mostly in low- and middle-income countries. According to the WHO, about half of all cases of TB are found in eight countries: Bangladesh, China, India, Indonesia, Nigeria, Pakistan, Philippines, and South Africa.

Reducing Poverty, Prevention, and Screening

Why is TB so prevalent in these countries? An estimated 1 in 4 people worldwide are infected with TB, but they do not have TB disease. It is only when immunity is impaired that latent TB becomes an active TB infection. A weakened immune system can be caused by diseases, such as HIV and diabetes, but it’s the combination of malnutrition and poor hygiene that gives rise to so many cases of TB.

Another reason for the spread of the disease is that its symptoms (coughing, chest pain, fever, weight loss) are the same as in other respiratory illnesses and may be overlooked even by health care professionals. Of the estimated 10 million people who have active TB, nearly 30-40% are undiagnosed and are able to infect others. This is why early detection is critical.

New Diagnostic Tools

The typical method of diagnosing TB is by using the sputum test, which is a collecting a patient’s sputum, or mucus, that’s coughed up from the lungs, after which the culture is stained and observed under a microscope. This is essentially the same test used by Robert Koch to identify Mycobacterium tuberculosis. Molecular methods are faster and more precise, but are too expensive and unfeasible to use in, e.g., rural clinics in low-income countries.

Fortunately, easier methods of diagnosis are in the pipeline, including the use of fluorescent probes in sputum, or conducting simple blood or urine tests with minimal equipment. Tongue swabs could be an alternative to testing those who have trouble producing sputum, such as young children. AI is already being used to analyse chest X-rays for signs of TB, which could be particularly beneficial in countries where there is a shortage of radiologists.

Treatment Without Relapse

TB is preventable and treatable, yet it’s by no means an easy path. The current standard treatment is 4-6 months of daily high doses of antimicrobials; however, rates of drug-resistant TB can be as high as 11%, making treatment even more costly and difficult to follow for many patients. As the current BCG vaccine has varying efficacy, there are high hopes for a new effective TB vaccine, with 21 candidates now undergoing clinical trials.

The End TB Strategy

In 2014, the World Health Assembly adopted the End TB Strategy, which ambitiously aims to eliminate TB: decreasing TB incidence by 90% and TB mortality by 95% between 2015 and 2035. Yet, global trends of incident TB cases have been at the same levels for the past decade and although rare, case numbers are rising in high-income countries. Investment in research is fundamental to lessen the burden of this disease, but many of the lessons learned during the COVID-19 pandemic can be put into place to curb TB, such as widespread screening, community-facing programmes, data collection and collaboration between public health systems in different regions. With a shared effort, perhaps TB can become the infectious disease of the past in low- and middle-income countries as well.