A number of the recent cases of Covid-19 among foreign workers here are those who had previously been in the dormitories but were later placed in quarantine facilities after they were exposed to others who were infected.

They were moved to the facilities before the dormitories had been cleared, the Ministry of Health's director of medical services Kenneth Mak said yesterday when asked where the foreign workers among recent Covid-19 cases had been infected.

These cases are being picked up now because the workers are reaching the end of their quarantine periods and are being tested, he added.

For these cases, evidence and testing suggest that many of them have older infections that occurred before they were even placed in the quarantine facilities, said Associate Professor Mak.

He said: "We have been looking very carefully also to make sure that we are able to pick up any possible re-infections of cases that may have occurred from recovered cases before. To date, we have not picked up any such case."

There are currently about 14,000 migrant workers in quarantine.

Other foreign worker Covid-19 cases are picked up from the routine testing that is in place for those who are returning to work, he said.

The task force is continuing to look at testing workers outside of the dormitory setting, such as those who were decanted to other facilities early on while the authorities were managing the coronavirus outbreak within the dormitories, said Prof Mak.

Health Minister Gan Kim Yong said those in quarantine facilities had been exposed to Covid-19-positive patients and so had a high risk of becoming patients themselves.

"We are still in the process of clearing these quarantined workers. Over time, this number will come down," he said.

But in time, there will be new infections, and more migrant workers who are exposed and have to be quarantined.

Hence, the number of such quarantined workers will stay at a certain level, and a number of them will be expected to be Covid-19-positive, he said.

He added that as all the dormitories have been cleared, most of the workers will be going back to work or have already done so.

As there will be more migrant workers in the workplaces and more workplace interactions, the number of Covid-19 cases in these settings is expected to go up, said Mr Gan.

"Therefore, it is very important for us to re-emphasise the safe management and safe distancing measures at workplaces so as to reduce the risk of transmission in workplaces," he said.