Incidence of Tuberculosis

Mrs Lina Chiam asked the Minister for Health in the last five years (a) what is the number of (i) people infected with tuberculosis; (ii) students infected with tuberculosis; (iii) foreigners in Singapore infected with tuberculosis; (iv) adult Singaporeans infected with tuberculosis; (b) what is the current number of infected patients who are under treatment; and (c) what are the measures the Ministry has adopted so far to prevent an outbreak of this contagious and dangerous disease.

Minister of State for Health (Dr Amy Khor Lean Suan) (for the Minister for Health): Sir, please allow me to first explain the difference between active tuberculosis (TB) and latent TB infection. Active TB is a disease state where the patient is symptomatic and the disease can spread to others. Latent TB infection is an asymptomatic disease state during which the disease cannot spread to others.

The majority of people with latent infection, about 90%, will not develop active TB disease. Only about 10% of persons with latent TB infection develop active TB disease. This may take place many years after the infection, although there is a higher risk of active TB during the first two years of infection. On average, about 1,380 Singapore residents were diagnosed with active TB each year over the last five years, or about 40 cases per 100,000. Most, or about 95% of these cases, are adults. Among non-residents excluding short-term visitors, the average number was also about 40 cases per 100,000 over the same period, or about 450 per year. Short-term visitors were excluded as many of them were workers who were diagnosed during pre-employment medical screening for application of work passes, and will be rejected if they were found to have TB. Others were here specifically for TB treatment. There were about 100 students diagnosed with TB each year during the last five years. More than 75% were students aged 17 years or older. About 1,000 people are currently being treated for TB.

I would like to highlight that Singapore has one of the lowest incidence rates of TB in Asia, besides Japan. Singapore has a comprehensive national TB control programme which was enhanced in 1997 with the setting up of the Singapore Tuberculosis Elimination Programme (STEP). Under STEP, the key control strategy for TB is, firstly, early detection and effective treatment. This is important to stop the spread of TB in the community. Secondly, the TB Control Unit, which runs STEP, closely monitors compliance with treatment until cure. Whilst most patients would voluntarily be compliant with the treatment, the Infectious Diseases Act gives us the power to mandate treatment of TB patients who are non-compliant, if necessary. By actively monitoring the treatment process of all TB cases, the risks of treatment failure and development of multi-drug resistance are lowered

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Finally, as TB could only be transmitted through prolonged close contact, contact-screening is conducted among household contacts and other close contacts in institutions like schools to identify persons with latent TB infection. Persons with latent TB infection are offered preventive treatment to reduce the likelihood of developing active disease. My Ministry will continue to monitor the effectiveness of the TB control programme closely, and implement enhancements from time to time.

Mrs Lina Chiam (Non-Constituency Member): Sir, I thank the Minister of State for answering my question. I have a supplementary question. I believe when foreign workers apply for work passes, they have to undergo X-rays to detect whether they have got TB. Am I correct? If the X-rays show black spots, it would be easy to presume it might be TB. Is there any other way to detect infection other than black spots on the X-rays?

Dr Amy Khor Lean Suan: For foreign domestic workers, before they are granted the Work Permit, they have to undergo medical screening, as the Member has rightly noted. And we screen for active TB. As I have said earlier in my reply, active TB cases are symptomatic cases. This is a disease state where the disease can be spread to others in the community. We do not screen for latent TB cases. If they are found to have active TB, they will be rejected and sent home. When a foreign domestic worker re-applies for a Work Permit, she would be screened again. The screening is done every time they apply for a Work Permit. The reason being that we feel that active TB can present itself in between screenings. The best way to prevent the spread of such a disease would be to get foreign domestic workers to go to the doctor, especially if they have a chronic cough, because that is the main symptom of TB.

Mrs Lina Chiam: Sir, I would like to ask the Minister of State whether it means that when a foreign worker applies for a work pass and has undergone a screening test or an X-ray, there is no way to identify whether they have active TB or not, is it, if there are no spots on the X-ray?

Dr Amy Khor Lean Suan: We screen them for active TB, and if they are confirmed to have active TB, they will not be given the Work Permit, and they will be sent home. I have also said in my reply that we do not screen latent TB because the risk of these cases developing into active TB is actually very low. Only about one in 10 of such cases will develop into an active TB case, and it could develop over the course of many years. Of course, the risk will be higher in the first two years – 50%. But the risk is spread over a lifetime, so it is very low. We do not screen for latent TB.

Mrs Lina Chiam: So X-rays are not really a means to test whether they have got TB or not.

Dr Amy Khor Lean Suan: No, no. I have just confirmed that the test that they have gone through will screen for active TB. The test is robust in that sense.