SINGAPORE - Recovered workers who test positive for Covid-19 may not have been reinfected, as they could just be shedding viral fragments from an old infection, said the Ministry of Manpower (MOM).
More recovered workers are expected to test positive for the coronavirus as the authorities conduct regular testing of those who were infected more than 270 days ago, due to the risk of waning immunity and the threat of new variants.
"We expect a proportion of them to return a positive result on the polymerase chain reaction test," said MOM on Wednesday (April 28).
MOM's Assurance, Care and Engagement (Ace) Group medical director, Dr Lam Meng Chon, said such cases will require further clinical assessment over several days, to determine whether they are old or current infections.
"When Covid-19 positive cases are found among the recovered workers population, it does not mean that it is a confirmed cluster because it could actually be a group of people that are shedding dead viral fragments, which are actually non-infectious," Dr Lam told reporters on the sidelines of a briefing.
"In this case, it is not a cluster but an old infection. So there is no need to panic, but to actually be patient and allow the clinical assessment to take place."
He was referring to the 24 recovered workers at Westlite Woodlands dormitory who tested positive for Covid-19. Of this group, five were determined to be likely cases of reinfection, while 11 were assessed to be shedding virus fragments.
Two of them were determined to be negative after retesting, while the remaining six cases are pending assessment by an expert panel.
On April 22, the Health Ministry's director of medical services, Associate Professor Kenneth Mak, said investigations to establish if a person is a reinfection case would usually take about two to three days, but up to two weeks in some cases.
On Wednesday, MOM said movement restrictions or quarantines in dormitories might be imposed if a few workers there test positive for Covid-19.
Such measures are necessary while the clinical assessment is carried out, and will be lifted when tests have concluded, added the ministry.
MOM said: "If quarantines are imposed in some dormitories, this does not necessarily mean that there are confirmed clusters there. Most of the time, it is because cases are being assessed to determine if they are old or current infections."
Dr Lam said imposing a quarantine will allow the authorities to quickly isolate cases of reinfection and prevent further spread of the disease.
He set out two scenarios for recovered workers who test positive in polymerase chain reaction tests.
One: The person is a prolonged shedder of Covid-19 and does not pose a threat to public health as he is non-infectious.
Two: The person is a reinfection case, which means that he has gotten infected from a different Covid-19 strain.
In the second case, the person is infectious and poses a risk of spreading the virus to others, Dr Lam said. Measures must thus be taken to curb further transmission.
There is no need for the public to be worried as the appropriate public health measures will be put in place early, he added.
Asked how workers will be taken care of should they be quarantined while clinical assessments are taking place, Dr Lam said their well-being is of utmost importance to the ministry.
He outlined several steps MOM has taken, including distributing care packs to workers and providing timely updates on a smartphone app for foreign workers.
"Beyond this, we are also working with the various non-governmental organisations such as HealthServe and Migrant Workers' Centre to help assure the workers who are quarantined at this moment," he said.