Primary Sources of Infection for Tuberculosis in Singapore

Mr Speaker, tuberculosis (TB) is an air-borne infectious disease. One can be infected with TB through close and prolonged exposure to a person with active TB, such as household members, co-workers and classmates. When infected, most will develop latent TB. Persons with latent TB do not have symptoms and are not infectious. The elderly and persons who have weakened immune systems, such as those with severe medical conditions, are more likely to develop active TB. About one in 10 healthy persons with latent TB will progress to active TB at some point during their lifetime.

To control the spread of TB, the Tuberculosis Control Unit (TBCU) adopts four strategies to detect, treat and prevent transmission that are in line with the World Health Organization’s recommendations. These are:

(a) Early detection and prompt treatment;

(b) Ensuring compliance to treatment through directly observed treatment;

(c) Close monitoring of treatment progress; and

(d) Tracing and screening of close contacts of infectious cases to identify infected contacts early and offer those with latent TB preventive treatment.

In addition, to prevent the importation of TB into Singapore, foreigners applying for work permit in Singapore are screened for active TB.

To further strengthen TB management among the medical community, the Ministry of Health (MOH) launched the TB clinical practice guidelines in 2016. These equip the medical community with better knowledge on TB diagnostic tools, treatment regimens and public health measures for TB control. To deepen our understanding of TB transmission and develop better control strategies, TBCU is progressively implementing whole genome sequencing for TB cases. This helps to identify related TB clusters more precisely and improve our ability to prevent TB transmission.

Specifically on multi-drug resistant TB (MDR-TB), TBCU will be implementing rapid DNA tests for drug resistance testing of all TB cases, reducing the testing duration from eight weeks to just a few hours. By ensuring that TB patients adhere to treatment through Directly Observed Therapy, it has been shown to reduce treatment failures and development of drug-resistant TB.

I thank the Senior Minister of State for his reply. I have two supplementary questions. First, earlier this year, MOH released an update that two in three new cases reported last year in 2017 were aged 50 and above and up to 30% of older residents in Singapore have latent TB. From the Senior Minister of State's earlier reply, about 10% of those with latent TB can possibly develop the active form. My first question is: with an ageing population, will the number of patients with active TB continue to increase further, with the growing numbers? If so, are there plans to have more targeted public education, public awareness, for this group of older Singaporeans to maybe make them more aware about what signs to look out for, what precautions to take? That is my first question.

My second question is: last year, there was a case reported – a staff member at a preschool in Clementi was diagnosed with active TB and then subsequent screening found that 39 children and four other staff members were diagnosed with latent TB. Are there any plans to screen staff, specifically, working at preschool centres to ensure better protection for our preschool children?

I thank Mr Melvin Yong for the two supplementary questions. Mr Melvin Yong is right to say that the prevalence of latent TB amongst the elderly Singaporeans is quite high, in the region of about 30%. The reason for that is because TB was endemic in Singapore and was very common until the 1970s. As a result, it is not unexpected to see the prevalence of latent TB to be higher within the older age group.

However, he is also right to say that not all patients with latent TB will develop active TB eventually. Five percent of those who acquired latent TB may get active TB within the first two years and another 5% may develop active TB within their lifetime. Based on these statistics, it is probably not necessary and not cost-effective to do screening or treatment of all patients with latent TB.

With regard to public education, yes, we have put up information on TB on our MOH websites and through press releases. In addition to that, the Health Promotion Board also runs a special social hygiene campaign to promote good hygiene practices and also to help prevent the spread of infectious diseases. During our annual World TB Day, TBCU also holds exhibitions at Tan Tock Seng Hospital to educate the public on TB. We will step up efforts on public education and we will also encourage the elderly to visit some of these exhibitions so that they are aware of the symptoms and what to look out for in case they do develop active TB.

With regard to the Member's second question on the screening of employees in preschools, under the Childcare Centres Regulations, all new staff members are required to undergo a medical check-up which includes a chest X-ray and be certified free from active TB by a registered medical practitioner before they can start work in a preschool centre. Centres are also advised to conduct daily health checks on their staff members and to monitor for persistent cough amongst staff members.

But I must caution that, sometimes, it can be difficult to diagnose TB because many of us do suffer from a bout of cough in one way or another throughout our lifetime and, unless the cough becomes persistent, then these employees should be encouraged to approach the medical practitioner to screen for active TB. Once the staff are diagnosed to have active TB, of course, they will not be permitted to return to work until they have been cleared to be fit for work by the medical practitioner.