By Dr Deborah Ng, Deputy Director, and Associate Professor Jeffery Cutter, Acting Director of the National Tuberculosis Programme, National Centre for Infectious Diseases
World Tuberculosis Day is observed internationally on 24 March each year. A look at how we can draw lessons from the latest pandemic COVID-19 to manage the world's oldest pandemic.
In 2019, there were about 10 million cases of tuberculosis (TB) reported worldwide. Despite being both preventable and curable, TB remains the leading cause of death from a single infectious agent globally. While countries have been putting in efforts to end TB, progress has been slow with only 9% reduction in the global TB incidence rate between 2015 and 2019, falling short of more than half the target of 20% set for 2020.
The Situation Today
2020 proved to be a challenging year, with the global COVID-19 pandemic overwhelming many countries and economaies. Efforts to accelerate TB control globally were significantly hampered by COVID-19, and it still threatens to derail the progress that countries have made towards ending TB. According to the World Health Organization's (WHO) Global Tuberculosis Report 2020, there were significant reductions in notification of TB cases. High burden countries for TB, specifically India, Indonesia and the Philippines, reported 25% to 30% drop compared to the same 6-month period in 2019. This reduction in case notification would likely lead to delayed diagnosis, increased transmission in the years to come, delayed treatment, and eventually cause a rise in deaths due to TB.
While the incidence rates of TB in Singapore have dropped from over 300 per 100,000 since the 1960s, the rates have not declined substantially over the last 15 years, ranging between 33 and 41 cases per 100,000 resident population since 2006. This highlights the need for renewed effort and commitment towards reducing TB. As TB had been common in Singapore until the 1970s, many older Singaporeans would have been exposed to TB and acquired latent TB then. This is reflected in the high proportion (71.9%) of TB cases who were 50 years old and above, among the new cases notified in 2020. Persons with latent TB do not exhibit symptoms and are not infectious, but 1 in 10 may progress to active TB during their lifetime. Delayed diagnosis among persons with TB has also contributed to these stagnating rates. This is in part due to delays in seeking medical attention by persons with symptoms, leading to ongoing transmission. In other instances, patients may seek medical attention, but the diagnosis may be missed by their clinician, especially among patients who 'doctor-hop'. Clinicians may initially prescribe antibiotics that lead to a temporary resolution of their symptoms, but recurrence of symptoms may lead them to seek an opinion from another doctor, who is unaware of the history. Without the complete clinical picture, the diagnosis of TB may not be made early.
'Teaching an old dog new tricks'
During the onset of COVID-19, we saw how widespread messaging is important in educating the community about health-seeking behaviour and good respiratory hygiene measures. Similarly, these measures are necessary to break the chain of transmission of TB. As such, ongoing education is important to maintain these good practices, and to serve as a reminder that TB is still endemic in Singapore.
During the pandemic, persons admitted to hospitals for suspected or confirmed COVID-19 infection would typically have a chest X-ray taken. As such, there were some who were opportunistically diagnosed with TB. Even among clinicians, the diagnosis of TB can be easily missed, especially if the patient does not have prolonged symptoms or only has subtle changes on their chest X-ray. It is therefore important to maintain a high index of suspicion among persons presenting with prolonged cough, or unexplained persistent changes on their chest X-ray.
The use of digital platforms increased exponentially during COVID-19 as people increasingly began to work from home and meetings moved online. TB treatment also went online with the use of video-observed therapy (VOT) successfully implemented for selected patients with TB. Persons with TB are typically required to take their medications in front of a healthcare worker as part of the course of treatment, also known as directly observed therapy (DOT). However, this places an onerous burden on persons with TB, especially those who are working as they may face pressure from their employers and colleagues when taking time off work for these daily visits. The use of VOT not only reduced travelling time and time off work for patients, but also offers greater flexibility and privacy. While DOT remains the gold standard for treatment administration, it is likely that the use of VOT will continue to increase. During the circuit breaker period, site visits which are an essential part of TB contact tracing, were greatly affected due to the restrictions in movement and closure of many workplaces. This in turn led to the implementation of virtual site visits, which allowed contact tracing to continue effectively.
Even with the COVID-19 outbreak in Singapore, the National TB Programme remained committed to its goal of detecting and treating TB in Singapore by ensuring continuity of services. In November last year, the programme moved towards whole genome sequencing (WGS) of all TB positive cultures in Singapore to study and detect genetic linkages in the laboratory. WGS results enable the National TB Programme to conduct more targeted epidemiological investigations. This narrows down the individuals for investigation and helps guide contact tracing and interviews conducted by the National TB Programme to sieve out information more rapidly and accurately, for example through social activities such as similar hobbies. The additional information has helped to improve mapping of TB clusters and made contact tracing of TB clusters such as the recent Singapore Pools Bedok Betting Centre more comprehensive while optimising the use of resources.
Singapore took a Whole-of-Government and Whole-of-Nation approach in managing COVID-19 over the last year. If we apply the same principles to control TB, with the primary goal of ending TB in Singapore, we can be confident to see a reduction in the incidence in the years to come.