Latent Tuberculosis: The Silent Threat — Ruthashini Selvasingam, Tan Cia Vei & Assoc Prof Dr Rafdzah Ahmad Zaki

Latent TB poses a significant public health challenge, sheltering the potential to turn into active disease and thereby continue the cycle of transmission.

In the global battle against infectious diseases, tuberculosis (TB) remains a significant challenge.

While much of the focus is on active TB cases, a silent and often overlooked aspect of this epidemic is latent tuberculosis infection (LTBI).

Latent TB poses a significant public health challenge, sheltering the potential to turn into active disease and thereby continue the cycle of transmission.

Tuberculosis, caused by the bacterium Mycobacterium tuberculosis, is a leading cause of infectious disease mortality worldwide, with millions of new cases annually.

However, not everyone infected with TB bacteria becomes sick. In many cases, the bacterium enters a dormant state, resulting in latent TB infection.

People with LTBI are asymptomatic and not contagious, but they stand a risk of the infection progressing to active TB disease, especially if their immune system weakens.

The World Health Organization (WHO) has estimated that nearly a quarter of the world’s population possess LTBI, with a significant portion at risk of developing active TB.

The risk is higher in individuals with compromised immune systems, such as those with HIV/AIDS, diabetes, or those undergoing treatments that weaken the immune response, and healthcare workers who might have multiple exposure to the disease.

The transition from latent to active TB can be a ticking time bomb, threatening not only the health of the individual but also public health at large.

The challenge with LTBI is its silent nature; since it does not manifest symptoms, it often goes undetected without specific testing. Testing for LTBI is crucial for individuals at high risk, including close contacts of people with active TB, people with HIV, and those who have recently immigrated from countries with high TB incidence.

The primary tests for LTBI are the Tuberculin Skin Test (TST) and the Interferon-Gamma Release Assays (IGRA). Identification of LTBI provides a critical window of opportunity for intervention before the infection progresses to active disease.

Treatment of LTBI plays an important role in TB control efforts. Without treatment, about 5 to 10% of infected persons will develop TB disease at some time in their lives.

Recent advancements in treatment regimens offer shorter, more tolerable options compared to the traditional months-long therapy.

The WHO recommends several treatment regimens, including shorter courses like the three-month regimen of weekly isoniazid and rifampicin, which has shown high efficacy and better completion rates.

Treating LTBI, especially among high-risk populations, can significantly reduce the risk of progression to active TB and is a key element in the strategy to eliminate TB as a public health threat.

The cost of treating LTBI is also far cheaper compared to the TB treatment.

The fight against TB requires a multifaceted approach that includes LTBI management.

As we observe World Tuberculosis Day, it is important to remember that the key to combating TB lies not only in treating active cases but also in addressing the silent reservoir of latent infections.

In this crucial journey towards TB elimination, the message is clear: tackling the silent threat of latent TB is not just a matter of public health urgency but a necessary step towards a TB-free world. Let’s not wait for the ticking bomb of latent TB to detonate.

Ruthashini Selvasingam, Tan Cia Vei and Assoc Prof Dr Rafdzah Ahmad Zaki are from the Department of Social and Preventive Medicine, Faculty of Medicine, University of Malaya.

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