The recent community cluster at the Bukit Panjang integrated transport hub is a cause for concern, although its emergence did not surprise experts.
With the easing of restrictions and more people going about in public, the formation of such clusters is to be expected, Professor Teo Yik Ying, dean of the National University of Singapore's Saw Swee Hock School of Public Health, told The Straits Times yesterday.
Still, there is reason to worry because the cluster - involving four SMRT bus captains who tested positive for Covid-19 between July 7 and last Friday - posed a relatively higher infection risk to fellow bus drivers than to commuters, said Prof Teo.
The reason is these drivers, who are front-line workers, would likely have had sustained interactions with the infected cases during break or meal times when they may not have been wearing masks, he said.
But for commuters, the risk is likely to be low as most would probably have had only transient interaction with the drivers and been masked up, he added.
The infected bus drivers drove services 976, 184 and 176, and three of them contracted the virus at home.
Since the cluster was confirmed last Friday, SMRT said on Sunday that it has taken steps to curb the spread of the virus.
Its chief communications officer Margaret Teo said employees have been urged not to talk during mealtimes when they are sitting close to one another, and to continue monitoring their health diligently.
"Employees who were in close contact with the (infected drivers) have been placed on leave of absence," she added.
All premises, such as depots and interchanges, are cleaned and disinfected frequently. Buses are also disinfected at least twice daily.
SMRT has advised its bus drivers to strictly follow safe management measures.
"Additional measures to sanitise the affected premises have been implemented too," said Ms Teo. These include closing the two canteens as well as the crew rest rooms, toilets and passenger service office.
"All common premises have undergone deep cleaning and disinfecting by an external vendor," she added.
Prof Teo said that while a cluster is bad news, what is more important is the speed at which the authorities can ring-fence these community infections, and how well contact tracing is done to identify and isolate those exposed as quickly as possible.
Associate Professor Alex Cook, vice-dean of research at NUS' Saw Swee Hock School of Public Health, said that it is better to have four linked cases than four that are unlinked.
Contact tracing will be easier with linked cases, he added. "Therefore, I am not especially worried by this particular cluster."
With the virus set to stay for the long term, Singaporeans will need to learn to live with it, said Professor Dale Fisher, a senior consultant at the division of infectious diseases at National University Hospital.
"This requires community behaviour to stay in line with all the guidelines and rules," he said.
• Additional reporting by Ng Keng Gene