TB or not TB? Exploring tuberculosis

In 2022, a HDB block in Jalan Bukit Merah was linked to a cluster of seven patients diagnosed with Tuberculosis (TB). This led to the mandatory screening of affected residents and workers in the block. A further cluster of 10 patients with TB was later found to be linked to the cluster, prompting the extended mandatory screening exercise for the residents and people working in the vicinity in January 2024 as a precautionary measure. During the exercise, voluntary screening was also offered to frequent visitors to the area.

TB remains a global public health threat. In 2022, it was estimated that there were approximately 10.6 million cases of active TB globally with approximately 1.3 million TB related deaths1. In the same year, in the course of the COVID-19 infection pandemic, TB was still the world’s second leading cause of death from a single infectious agent¹. In Singapore, TB is considered endemic. According to the Ministry of Health Singapore (MOH), 1,251 new cases of active TB among Singapore residents were diagnosed in 2022².

What is Tuberculosis?

TB is a contagious disease caused by the bacteria, Mycobacterium Tuberculosis. Transmission of the bacteria usually occurs through inhalation of aerosol droplets containing the bacteria. This usually happens with close and prolonged exposure to an infectious individual with untreated TB disease of the lungs or throat. After infection, one could be well and asymptomatic or develop symptoms such as fever, fatigue, cough, weight loss or night sweat. TB could also spread beyond the lungs and affect other organs, leading to a variety of symptoms related to the organs affected. For example, an individual with TB affecting the brain could experience fever, headaches, confusion or neurological deficits; an individual with TB affecting the intestine could experience fever, chronic diarrhoea, abdominal pain or weight loss.

Infected persons with respiratory symptoms are considered to have an active and potentially contagious TB disease. On the other hand, infected individuals who remain asymptomatic are considered to have a latent TB infection (LTBI). LTBI is characterised by inactive bacteria and is deemed non- transmissible. However, about 5-10% of individuals with LTBI could eventually be afflicted with the active disease during their lifetime.

Prolonged, unprotected exposure with an infected person with contagious TB is usually required for acquiring the infection. A person does not typically contract TB infection from casual person-to-person contact (e.g., handshake, using public/communal utensils or toilets). Nonetheless, early identification and treatment of infectious cases in combination with self-isolation practices is crucial in reducing the risk of infection transmission.

Will Tuberculosis affect the heart?

There is some association between TB infection and cardiovascular disease. Some studies suggest that TB infections are linked with the hardening of the arteries, and could place an individual at higher risk of developing cardiovascular disease – which has been hypothesised to be secondary to the systemic inflammation that TB causes^{3, 4, 5, 6, 7}.

Although TB infection commonly affects the lungs, other organs may be involved. Infections involving the heart are serious disease and are due to the inflammation of the heart muscles and exterior lining (pericardium) of the heart. Patients may present with symptoms of heart failure and chest pain. In such cases, prognosis is poorer and can lead to higher risks of heart failure and death.

The treatment of TB involves the use of anti-tuberculosis antibiotics, some of which may have interactions with other medications given for patients with heart disease. Attending physicians are able to assess the optimal tuberculosis treatment regime based on one’s clinical needs and monitor and minimise any side effects over the course of therapy. Diabetes, which is a leading risk factor for heart disease, also places an individual at higher risk of TB relapse and death.

TB is curable and the spread of TB is preventable. Timely diagnosis and treatment of TB infections remain the cornerstone of infection prevention. Individuals who are unwell and display symptoms of TB should seek medical attention as soon as possible.

Individuals with asymptomatic LTBI should also consider LTBI treatment to reduce the risk of developing the active disease and the potential spread of infection. National control measures are also in place to reduce the risk of TB transmission – these include health screening of individuals who are at higher risk of acquiring the infection and the treatment of individuals with LTBI.

Article is contributed by Dr Cheong Hau Yiang, Associate Consultant, Department of Infectious Diseases at the Changi General Hospital.

References

1. (2023, November 7). Tuberculosis. World Health Organization. Retrieved February 20, 2024, from https://www.who.int/news-room/fact-sheets/detail/tuberculosis
2. (n.d.). Tuberculosis. Ministry of Health Singapore. Retrieved February 20, 2024, from https://www.moh.gov.sg/diseases-updates/tuberculosis
3. Adefuye, M. A., Manjunatha, N., Ganduri, V., Rajasekaran, K., Duraiyarasan, S., et al. (2022). Tuberculosis and Cardiovascular Complications: An Overviewq. National Library of Medicine. https://doi.org/10.7759/cureus.28268
4. Wongtrakul, W., Charoenngam, N., & Ungprasert, P. (2020). Tuberculosis and risk of coronary heart disease: A systematic review and meta-analysis. National Library of Medicine. https://doi.org/10.1016/j.ijtb.2020.01.008
5. Huaman, M. A., Ticona, E., Miranda, G., Kryscio, R. J., Mugruza, R., et al. (2018). The Relationship Between Latent Tuberculosis Infection and Acute Myocardial Infarction. National Library of Medicine. https://doi.org/10.1093/cid/cix910
6. Hasanain, A. F. A., El-Maghraby, K. M., Zayed, A. A. H., Nafee, A. M. A., & Abdel-Aal, S. M., et al. (2018). Latent tuberculosis infection among patients with coronary artery stenosis: A case-Control study. National Library of Medicine. https://doi.org/10.4103/ijmy.ijmy_34_18
7. Chung, W. S., Lin, C. L., Hung, C. T., Chu, Y. H., & Sung, F. C., et al. (2014). Tuberculosis increases the subsequent risk of acute coronary syndrome: A nationwide population-based cohort study. National Library of Medicine. https://doi.org/10.5588/ijtld.13.0288