askST: Should I be worried about 3 tuberculosis clusters in Bedok Central?

SINGAPORE – A five-day public screening exercise for tuberculosis is under way, with the Communicable Diseases Agency (CDA) attempting to detect and prevent the spread of the infectious disease in the community after three tuberculosis (TB) clusters were detected in Bedok Central.

CDA announced on April 30 that some of the 13 individuals in the clusters had likely been infected through repeated visits or prolonged exposure at three key locations: Heartbeat@Bedok, Block 216 Bedok Food Centre and Market, and the Singapore Pools Bedok Betting Centre at Block 215 Bedok North Street 1.

The Straits Times looks at this endemic disease and what could have brought about the latest clusters.

What causes tuberculosis?

Caused by Mycobacterium tuberculosis, TB usually affects the lungs but can also affect other parts of the body.

Symptoms of TB disease include a persistent cough that lasts more than two weeks, low-grade fever, night sweats, fatigue, weight loss and chest pain, said CDA.

How is it transmitted?

TB spreads when a person with an active TB infection coughs the bacteria into the air, which others then inhale through close, prolonged contact, said CDA.

Transmission of the TB bacteria usually requires prolonged exposure over days or weeks of contact, rather than minutes or hours.

CDA emphasised that a person cannot get TB from sharing cups, utensils or food. It is also not spread through shaking hands, kissing, and touching bed linen or toilet seats.

How does it affect the body?

According to information on the US Centers for Disease Control and Prevention’s (CDC) website, TB bacteria inhaled into the lungs can settle and begin to grow.

TB bacteria can live in the body without making the person sick. This is known as a latent TB infection.

Such people do not feel sick, do not have symptoms and cannot spread TB to others, said CDC.

Without treatment, people with latent TB can develop active TB disease if the immune system cannot stop the bacteria from multiplying and growing in the body, said CDC.

CDA said the disease develops in the first two years for 5 per cent of those infected. Another 5 per cent may develop TB later in life, especially as they age.

People with active TB disease feel sick with symptoms, and may also be able to spread the germs to people they spend time with every day, said CDC.

Should we be worried about 3 TB clusters forming in Bedok Central?

TB is endemic in Singapore, with ongoing transmission, though the number of TB cases is relatively low. There were 1,019 new cases of active TB disease among Singapore residents in 2025, a drop from the 1,156 in 2024.

CDA said it has not seen any unique factors influencing or driving new TB transmission in Singapore.

Besides sufferers having to be exposed for a long period or be in close contact with a sick person to then be infected, TB is also generally treatable.

Those with active TB will be treated with a combination of drugs for six to nine months. Patients are generally no longer infectious two weeks after treatment starts, and can probably resume their normal activities.

However, completing the treatment is still necessary to prevent any relapse, said CDA.

Those with latent TB can also receive preventive treatment with anti-TB antibiotics over four to six months. This helps reduce their risk of developing active TB in the future, added CDA.

Senior Minister of State for Health Tan Kiat How said in several of his Facebook posts that none of the 13 TB cases was a hawker or staff member working at the three key locations, and they were visitors to the Bedok Central area.

Why was public screening launched only after three clusters were detected?

CDA said that the three clusters occurred simultaneously, rather than one cluster forming after another.

Through whole genome sequencing of the cases as well as epidemiological investigations, CDA found that the three clusters of 13 cases occurred in the same locality over the same time period, and further public health actions were needed to reduce further transmission.

This led to the decision to launch the screening exercise.

Whole genome sequencing is the process of determining the DNA sequence of an organism’s genome. Determining the TB bacteria’s genome casts light on whether seemingly unconnected patients have been infected by genetically similar bacteria, suggesting possible links.

In addition, some of the cases were genetically linked to earlier clusters, which were also related to the same betting centre. The Ministry of Health conducted similar public screening for visitors who frequented the centre in 2021.

CDA said that due to the nature of TB, which can cause an infected person to develop the disease several decades later, the latest analysis could be made only when new cases emerged. It led the agency to look for more commonalities beyond the betting centre and identify other locations where TB spread may have occurred.

CDA said that whole genome sequencing has enabled it to detect genetically similar TB cases.

Therefore, identification of TB clusters from time to time is expected.

Does my BCG vaccination protect me against TB?

CDA said the TB vaccine, or Bacillus Calmette-Guerin (BCG), given at birth is effective at preventing serious forms of TB in young children. This includes TB meningitis, which affects the linings of the brain.

However, it does not strongly protect against lung TB, which is the most common form of TB in adults.

The BCG vaccine reduces the risk of developing all forms of TB by 50 per cent, and deadly forms of TB by up to 80 per cent, said Professor Thoon Koh Cheng, senior consultant of the KK Women’s and Children’s Hospital’s infectious disease service.

The risk of long-term disability and death is high in children infected with TB, added Prof Thoon.