Strategies used in tackling Covid-19 can help to eliminate TB in S’pore
We commemorate World Tuberculosis (TB) Day every March 24. The experiences of the past year have shown a silver lining for TB elimination.
We commemorate World Tuberculosis (TB) Day every March 24.
Since Dr Robert Koch discovered the bacterium that causes TB 139 years ago, we have made great strides towards eliminating the disease that killed approximately one out of every seven people in Koch’s time.
Better diagnostic tests allow for the detection of TB not just in its active, symptomatic and contagious phase, but also when the bacterium is latent in the body, contained by the immune system and incapable of spread.
The Bacille-Calmette-Guerin (BCG) vaccine has reduced childhood deaths from TB worldwide, even though it is not particularly effective in adults.
Anti-TB drugs have cured millions worldwide and also reduced the transmission of the bacterium at the same time.
In Singapore, TB rates had fallen sixfold from over 300 per 100,000 population in 1958 — the year it became compulsory for healthcare providers here to report suspected or confirmed cases to the authorities — to just over 50 per 100,000 population in 1985, when short course (six months) treatment for TB became routine.
Yet, the global burden of TB is so great that political commitment, advocacy and innovation continue to be crucial for its elimination.
This is especially if we are to achieve the World Health Organization's ambitious End TB Strategy, which aims to reduce deaths due to the disease by 95 per cent and new cases by 90 per cent by 2035.
March 24 marks the second World TB Day commemorated during the Covid-19 pandemic, which has had an adverse and longer-lasting impact on TB elimination in many countries.
The great fear last year was that Covid-19 would roll back achievements in TB prevention and control worldwide, not just via the diversion of funding and healthcare resources from TB public health and treatment programmes, but also by reducing both active TB case finding and treatment completion rates.
This fear has been borne out by data from nine countries in Asia, Africa and Eastern Europe that collectively represent 60 per cent of the global TB burden.
In these countries, TB diagnosis and treatment declined in 2020 by an average of 23 per cent (representing approximately one million fewer cases) compared with 2019, falling back to levels last seen in 2008.
It will take considerable resources and effort to regain lost ground.
The incidence of TB also fell slightly in Singapore last year compared to 2019, although this is likely not primarily due to healthcare disruptions nor the diversion of resources away from the Singapore TB Elimination Programme.
Nonetheless, the presence of the large TB clusters linked to the Bedok outlet of Singapore Pools, which also resulted in a screening exercise at Block 174D Hougang Avenue 1 in October 2020, shows that active interventions continue to be necessary.
The experiences of the past year have shown a silver lining for TB elimination.
While TB may never command the kind of resources and political commitment given to the pandemic, what has been and continue to be achieved within an ultra-short timeframe in the fields of public health, biomedical (including vaccine) development and societal resilience signal the potential for similar achievements with other diseases, including TB.
There are three key strategies specific to TB control: Diagnosing and completing the treatment of all persons with active TB; contact tracing to find and evaluate persons who have been in contact with those with active TB; and screening of populations at high risk of TB.
For the latter two strategies, the aim is to identify persons with latent or occasionally active TB in order to administer the appropriate treatment and prevent further transmission.
A potential fourth strategy is that of widespread vaccination, although a vaccine that is more effective than BCG is still lacking.
What else can be done in Singapore?
It is clear that virtually all of the metaphorical “low-hanging fruit” with regards to TB elimination have been plucked, and difficult interventions must now be attempted in order to fundamentally change the trajectory of TB rates here.
Yet the pandemic has offered lessons and possibilities that previously would not have been seriously considered.
Our country has an excellent TB treatment programme established by the TB Control Unit, with treatment completion rates that exceed 95 per cent.
However, delayed diagnosis has been a problem, with the majority of active TB patients here diagnosed after being symptomatic for more than three weeks.
A sustained campaign to de-stigmatise TB as well as educate both healthcare providers and the community may help, similar to communication campaigns to increase the uptake of Covid-19 vaccines.
Singapore’s contact tracing strategy for Covid-19 is one of the best in the world, and should be transferred and adapted towards improving TB contact tracing here, which lags behind many high income countries.
Additionally, a significant proportion of identified close contacts do not turn up for medical evaluation, as it is not mandatory to do so.
Given the potential public health threat, there is no reason why we should not make this mandatory, in line with practices in countries such as Japan and Australia.
Almost half of newly diagnosed TB cases in Singapore are foreign-born individuals from countries with high rates of tuberculosis.
All applicants for long term visit passes, work passes or permanent residency are screened for active TB via short surveys and chest X-rays, but not for latent TB, which requires a blood test.
Hence, the majority of potential TB cases are missed, unlike in many high-income low TB-incidence countries such as the United States, Australia and Japan where latent TB testing in migrants is the norm.
Uncertain cost-effectiveness has been given as the reason for not implementing latent TB testing for migrants here.
But given how we now test and quarantine virtually all visitors to Singapore for Covid-19, it is worth revisiting the issue again, with considerations of a strategy that could involve pre-departure or post-arrival testing and treatment, or both.
In conclusion, in order to eliminate TB in Singapore, we will need to implement difficult and challenging interventions rather than tweak existing operations and policies.
The Covid-19 pandemic has forced us to innovate and adapt, and many of the lessons as well as structures set up will help with TB elimination.
ABOUT THE AUTHOR:
Associate Professor Hsu Li Yang is vice-dean (Global Health) and head of the Infectious Diseases Programme at the Saw Swee Hock School of Public Health, National University of Singapore. He was formerly clinical director of the National Centre for Infectious Diseases.