What more can Singapore do to eradicate tuberculosis?

March 24 was World Tuberculosis (TB) Day.

The World Health Organisation estimates that a quarter of the world’s population is infected with latent TB, of which 10 million developed active TB in 2017, resulting in 1.6 million deaths.

TB remains one of the top 10 leading causes of death worldwide, despite the fact that the rate of new TB cases has fallen in most countries.

Just under half a million people were infected by multidrug-resistant TB (MDR-TB) in 2017. Infection with MDR-TB — where the bacterium is resistant to the most critical anti-tuberculosis drugs — results in poorer health outcomes despite the use of more expensive and toxic drugs for a prolonged course of treatment (nine-24 months compared to six-nine months for drug-susceptible TB).

This global phenomenon is unlikely to decline in the short term, and may increasingly impact tuberculosis control in Singapore in the future.

Among residents and long-staying foreigners in Singapore, the rate of new TB cases had fallen from 307 per 100,000 residents in 1958 (the first year of mandatory TB notification) to a low of 35 per 100,000 residents in 2007, only to subsequently rise and hover around 40 per 100,000 residents since.

Fortunately, barring a few high profile incidents in recent years such as the Parklane cybercafé and Ang Mo Kio TB cluster which spanned between 2012 and 2016, the rate of MDR-TB in Singapore remains low.

Although this figure is a fraction of TB incidence in neighbouring South-east Asian countries, the continued stagnation is a cause of concern.

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Singapore has had a comprehensive programme of TB control based on the World Health Organisation-endorsed strategy of directly-observed therapy since 1997.

The objective of directly-observed therapy is to boost cure rates for TB at affordable costs, and its components have been refined to comprise:

• Sustained political and financial commitment to TB control.
• Availability of quality-assured laboratory diagnostics for TB.
• Regular and uninterrupted supply of high quality anti-TB medications.
• Standardised recording and reporting of cases and treatment outcomes.
• Standardised short-course anti-TB treatment administered under direct and supportive observation.

The most visible part of the programme is the administration of the six-nine month course of anti-TB treatment under the direct observation of nurses at the TB Control Unit and polyclinics.

This is understandably viewed as an inconvenience by the majority of the patients, who cannot travel extensively during their treatment and who have to have a nurse observe them consuming their medications most days of the week.

However, not all patients are required to submit to direct observation of treatment.

Those whose disease are deemed non-infectious - TB that does not affect the lungs but other parts of the body - are generally permitted to bring their medications home for self-administration, as they are not at risk of transmitting to others.

A small number of patients with TB of the lungs are also treated via self-administration of medications – most of these are treated in the private sector.

Whether anti-TB treatment needs to be directly observed is a contentious point.

A number of clinical trials and meta-analyses, including one performed by the renowned Cochrane Library group in 2015, have not shown any strong benefits of direct observation over self-administration.

Nonetheless, it is clear that directly-observed therapy as a whole has greatly improved TB treatment completion and cure rates worldwide.

There are few alternatives to TB control via cure.

Development of new anti-tuberculosis drugs and breakthroughs in other fields such as immunotherapy offer the possibility of shorter course and potentially less toxic drug regimens for both active and latent drug-susceptible and MDR-TB.

A recently concluded clinical trial in Africa of a new TB vaccine (M72/AS01E) demonstrated that it was both safe and reasonably effective, with a protective efficacy of approximately 54 per cent (an improvement on the venerable Bacille Calmette-Guérin vaccine).

Similarly, advances in tuberculosis diagnostics offer the hope of earlier diagnosis and confirmation of TB, which is important to prevent further spread of the disease. All of these breakthroughs, however, are still many years away from being widely available commercial products.

Harnessing of existing technology may facilitate directly-observed therapy.

The use of smartphones and computers for “video-observed treatment” of TB has been tested in several countries, notably the United States and United Kingdom.

This has been found to be both feasible and acceptable by both patients and TB programme staff, with treatment completion and cure rates that are equivalent to direct observation by medical staff.

Video-observed treatment of TB should certainly be a consideration here, where smartphone penetration is exceedingly high, provided that privacy safeguards are in place.

For Singapore, in addition to being early adopters and developers of interventions that show evidence for cost-effective TB control, there is a need to address the issue of stigma associated with the disease.

The question of unjust termination of employment for employees with TB was raised and addressed in Parliament in 2016, where the Minister for Manpower reassured the House that appeals against such unfair dismissals could be addressed to his ministry under the Employment Act.

He also urged employees suspected of having TB to seek medical care early and be adherent to the treatment, and for employers to treat such employees “with fairness and compassion” in order to minimise the risk of transmission of TB at the workplace.

Finally, having a public, ambitious target for TB control, such as has been achieved by Japan or several other high-income countries, might help to generate or focus resources.

There remains a critical need for the government, businesses and the Singapore community to be collectively and continuously engaged in TB control.

This is more important than whether biomedical breakthroughs, public-private initiatives and other innovative approaches to TB control are individually successful.

Such cooperation marked many of the advances made in reducing the burden of TB since post-World War II in Singapore – and will be equally crucial in the future.

ABOUT THE AUTHORS:

Assoc Prof Hsu Li Yang is Head of the Infectious Diseases Programme at Saw Swee Hock School of Public Health and Dr Loh Kah Seng is Director of Chronicles Research & Education, a research consultancy.