Covid-19 infections continue to surface in dormitories previously cleared of the virus, as many of the workers there have not been exposed and therefore remain susceptible to the virus, said Second Minister for Manpower Tan See Leng.
"However, we are prepared for this," he told a virtual press conference yesterday.
Since the dormitories were declared cleared nearly a month ago on Aug 11, there has been an average of 45 workers testing positive for Covid-19 daily, the Ministry of Health said in a statement.
These were detected primarily through active surveillance testing, such as rostered routine testing (RRT), and aggressive tracing and testing when a new case is detected. About 2 per cent of these newly detected cases had positive serological tests, indicating past infections.
When asked if some of the cases in the cleared dormitories had slipped through undetected by the polymerase chain reaction (PCR) tests, Dr Tan pointed out: "A PCR test is a test at that particular point in time. So it's a snapshot of the status of the migrant worker at that particular point in time. And it's also a function of picking up the virus at a certain concentration."
He said it is not a matter of the sensitivity, adding that the test kits used here are "very sensitive tests".
"It's just that at that particular point in time, in the cycle of the incubation, we may not have picked up the virus because the manifestation of it, the concentration has still not reached that level yet."
Because of this, the authorities decided to tighten the dragnet by rostering workers for testing every 14 days, a key lever in Singapore's detection strategy, said Dr Tan, who cited studies showing that up to 30 per cent of infected individuals are asymptomatic.
In 14 days, about 98 per cent of the migrant worker dormitory population can be tested, he noted.
"Now, does it mean we miss out the 2 per cent? No, because the moment we pick up a re-emergent sort of a number, we actually lock down the block and we test everyone.
"So we believe that this repeated testing... will allow us to weed out this thing and bring it under control."
Only about 15 per cent of dormitory residents began routine testing early last month, but a few weeks later, as more workers went on the roster, an increase in new cases was noted.
Currently, about 90 per cent of workers have been scheduled for the routine testing and "we expect to reach 100 per cent over the next few weeks", said Dr Tan.
"Early detection is critical as it helps to break the chain of transmission and reduce the number of infections subsequently. We will continue our efforts to detect new cases early, and isolate them."
Workers who have not yet registered for RRT cannot go out to work, he said. "So that is how we actually 'contain and quarantine' this group."
Adding that the routine testing is an effective and efficient measure, Dr Tan called on dormitory operators, employers and workers to work together with the authorities to minimise the risk of an outbreak.
Dr Tan noted that the authorities have successfully contained more than 200 re-emergent dormitory sites so far. In the majority of these sites, the number of re-emergent infections has been low, with fewer than 10 each.
Health Minister Gan Kim Yong, who co-chairs the multi-ministry task force tackling the Covid-19 pandemic, stressed that there is a risk of transmission in the community, as these dormitory residents may interact with fellow migrant workers and Singaporeans at their work sites.
"So there is a risk," he added. "What is crucial really is to ensure that in addition to the measures that we have imposed in the dormitories and the work sites, we need to continue to be quite tight in the safe distancing measures in the community. So that even if there's an infection in the community, we can reduce the risk of spread and reduce the risk of a large community cluster from forming."
Measures in place to tackle cases in dorms
To detect and contain new Covid-19 cases in dormitories, the Ministry of Manpower has put in place a "multi-layered strategy" with three main points.
1. TO PREVENT POTENTIAL INFECTIONS
"Safe Living, Safe Working and Safe Rest Day" measures have been implemented in the worker dormitories.
Before dormitory residents are allowed to return to work, dormitory operators have to implement various physical distancing measures to limit workers from mixing across rooms, levels and blocks, as well as when using common facilities and during transport to and from work sites.
Operators must also monitor their residents' health and take the necessary precautions so that those who are unwell are quickly isolated and provided with medical treatment.
2. TO DETECT NEW CASES SWIFTLY
The Ministry of Manpower has deployed a number of steps, including having workers self-monitor and update their health status regularly. Those who report sick with acute respiratory illnesses are observed closely.
Wastewater at selected dormitories is also tested for traces of the virus, and rostered routine testing (RRT) is conducted for residents every 14 days. The RRT, in particular, has helped to pick up new cases in the dormitories.
3. TO CONTAIN SPREAD OF VIRUS
Close contacts will be quarantined and must test negative at the end of their quarantine period before they can return to work. Aggressive testing operations within the dormitories will also be done based on the potential risk of spread.
The ministry will continue to adjust this strategy as new insights are gained about how the virus spreads.