Mandatory TB screening in Bukit Merah after emergence of more cases linked to 2022 cluster

SINGAPORE: Around 3,000 people who live and work in Bukit Merah will be screened for tuberculosis, after 10 more active cases were detected, all linked to a cluster first uncovered in 2022.

The screening, which is mandatory for some groups and voluntary for others, will start on Jan 11, the Ministry of Health (MOH) announced on Friday (Jan 5). The mandatory screening exercise is the largest to date. 

The cluster was declared in March 2022, following the diagnosis of seven tuberculosis cases among residents of Block 2 Jalan Bukit Merah between February 2021 and March 2022. 

The 10 latest cases were discovered between February 2022 and July 2023, and linked to the cluster through genetic analysis, said MOH in a press release. 

“This suggests that there had possibly been spread beyond Block 2 Jalan Bukit Merah to the immediate vicinity,” the ministry said. 

Of the 10 new cases, two individuals live in Block 1 Jalan Bukit Merah, one lives in Block 2 Jalan Bukit Merah, one works at the nearby ABC Brickworks Market and Food Centre and six frequently visited the market, said MOH. 

The mandatory screening, which will be free, will apply to those who live and work in Blocks 1 and 3 Jalan Bukit Merah, those who work at ABC Brickworks Market and Food Centre, as well as clients and staff of the Thong Kheng Senior Activity Centre in Block 3 Jalan Bukit Merah. 

This is the first time the government is conducting tuberculosis screening for patrons of a market or hawker centre, who would not typically be considered close contacts, said the National Centre for Infectious Diseases (NCID) in a media briefing on Friday. 

The on-site tuberculosis screening is being offered as a precautionary measure, to identify undetected active tuberculosis cases and prevent further transmission, the press release read. 

Unlike other infectious diseases, tuberculosis has a long latent period and may not develop into disease for months or even years later. 

In 2022, there were 1,251 new active tuberculosis cases in Singapore. Only active cases are infectious. 

Those with latent tuberculosis infections do not exhibit symptoms, are not infectious, and do not pose a public health risk, said MOH in the release. Tuberculosis is curable.

Voluntary screening, which will also be free, will be offered to several other groups. This includes people who frequently visit – or have spent more than 12 hours per month between November 2021 and January 2024 – the market or Blocks 1, 2 and 3 Jalan Bukit Merah. 

People who live or work at Block 2 Jalan Bukit Merah who did not undergo tuberculosis screening during the previous mass screening exercise from May 2022 to August 2022, and former residents and tenants of Block 1 and 3 Jalan Bukit Merah will also be eligible for free voluntary screening. 

Voluntary screening will also be offered to teachers and students of the PCF Sparkletots preschool located at Block 3 Jalan Bukit Merah.

HOW TO GET TESTED

Between Jan 6 and Jan 9, staff from MOH, NCID and the People’s Association will visit all units at the affected blocks and stalls to engage with residents and schedule appointments for the screening. 

From Jan 11 to Jan 13, staff from MOH and NCID will go door-to-door to conduct mandatory screening, which will involve a blood test, in the homes of residents of Blocks 1 and 3 Jalan Bukit Merah. 

Screening stations will be set up at the open-air car park next to Block 2 Jalan Bukit Merah from Jan 11 to Jan 15 for those who work at the blocks or ABC Brickworks Market and Food Centre. 

Those who are eligible for voluntary screening can make an appointment at go.gov.sg/tbs for screening at the car park from Jan 14 to Jan 15, and screening will strictly be by appointment only. 

Individuals who test positive for latent tuberculosis infection must then undergo additional evaluation, including a chest x-ray and other tests. They will also be offered preventive treatment to reduce their risk of developing active tuberculosis in the future. 

People with abnormal chest X-rays will be further evaluated at the Tuberculosis Control Unit, and treatment will commence if they are diagnosed with active tuberculosis, said the Health Ministry. 

Active tuberculosis is treated with a course of three to four medications, for six to nine months, said NCID at a media briefing earlier on Friday. 

Those with active tuberculosis feel better quickly after starting treatment and become non-infectious in about two weeks, but it is important for them to complete the entire course of treatment, NCID said. This is why these individuals have to go to a polyclinic every day and take their medicine under the observation of healthcare professionals. 

For those with latent tuberculosis infections, preventive treatment can reduce the risk of them developing active tuberculosis in the future, and this is 60 to 90 per cent effective, said NCID. This involves taking one type of medication for four to six months.  

About 10 per cent of those with latent tuberculosis infections will develop active tuberculosis disease in their lifetime, but the risk is higher in the first two years after they are infected, NCID added. 

MOH urged those who work and live in Blocks 1 and 3 Jalan Bukit Merah, as well as the market, to be screened for active and latent tuberculosis. It also urged those who experience tuberculosis symptoms, including persistent fever and coughing, night sweats, weight loss, fatigue, chest pain and blood in their sputum, to come forward to get tested. 

“The problem we have is that we have a lot of individuals who dismiss some of these symptoms, like coughing for three weeks,” said the MOH spokesperson during the media briefing on Friday.

“And the more it festers, it gets more serious, it’s more transmissible because their bacterial load becomes higher, and it is also more difficult to treat if you wait for too long.” 

HOW THE NEW CASES WERE UNCOVERED 

Transmission of the tuberculosis bacteria from active cases usually requires prolonged exposure – days to weeks of exposure rather than minutes to hours, said MOH in the press release. 

“A person cannot get tuberculosis from sharing cups, utensils or food. Tuberculosis is also not spread through shaking hands, kissing, touching bed linens or toilet seats,” the press release read. 

In the previous screening conducted in 2022, 197 cases of latent tuberculosis infection and 15 cases of active tuberculosis disease were found, and all the active cases were treated accordingly. Seven of the 15 active cases discovered in this round of screening are also part of the cluster.

When the 10 most recent cases were diagnosed between February 2022 and July 2023, contact tracing was conducted, but did not identify each other as close contacts, said the Health Ministry. 

It also alerted primary care physicians in the area in April 2023 to keep a lookout for patients who present with tuberculosis symptoms. 

Genetic analysis conducted by the National Tuberculosis Programme in September 2023 then revealed that all 10 cases have a similar genetic make-up to the cases in Block 2 Jalan Bukit Merah, linking them to the cluster. 

“Further detailed epidemiological investigations into the cases did not reveal any common links, other than that many of the cases frequented ABC Brickworks Market and Food Centre or lived in the vicinity,” the press release read. 

MOH was then notified of the cases in November 2023. 

The authorities conduct genetic sequencing for all discovered cases of active tuberculosis, and the process of cultivating the bacteria sample, conducting the genetic sequencing and then analysing the results takes time, said the MOH spokesperson at the media briefing. 

Even though many of the cases frequented the market, they all lived elsewhere, and there was no apparent link between them at first glance, they continued. 

After it emerged that the 10 cases were linked to the cluster through genetic analysis, NCID conducted thorough interviews with the individuals, which involved discussing months or years of their movements, since tuberculosis can remain latent for a long time. 

Though this was quite a challenge, this led to the realisation that all cases frequented ABC Brickworks Market and Food Centre, said the MOH spokesperson.