Among the recent infections is a one-year-old Singaporean baby who had arrived from India on August 24. He was the only imported case on Tuesday. On Monday, two of the three imported cases had arrived from India.
All travellers from India who are not Singaporeans and permanent residents will have to take a coronavirus test within 72 hours before departing for Singapore from next Thursday, in a move to reduce the number of imported cases from the country.
Among the recent infections is a one-year-old Singaporean baby who had arrived from India on August 24. He was the only imported case on Tuesday. On Monday, two of the three imported cases had arrived from India.
The travellers will have to present a valid negative test result that has to be taken within 72 hours before their flight to Singapore, the Health Ministry said in a statement late on Wednesday.
It said the move had been taken to reduce the imported cases from India.
"We have been closely monitoring the COVID-19 situation in India. There have been reports of a resurgence of infections in India. Singapore has also observed a significant number of imported cases with recent travel history to India," the ministry said.
"As the global situation evolves, we will continue to adjust our border measures to manage the risk of importation and any onward transmission to the community," it added.
The tests will apply on top of the existing requirements of a 14-day stay-home notice (SHN) at dedicated facilities and a negative COVID-19 test before the end of their stay-home notice.
Travellers should be prepared to be subjected to control measures upon entry, including the payment of their stay at the SHN facilities and tests, according to the ministry.
Meanwhile, a minister said coronavirus cases continued to surface in previously cleared dormitories that are housing foreign workers as many of the workers there had not been exposed before and, therefore, remain susceptible to the infection.
"However, we are prepared for this," Second Minister for Manpower Tan See Leng told a virtual press conference on Wednesday.
Since the dormitories were declared cleared of the virus nearly a month ago on August 11, there has been an average of 45 workers testing positive for COVID-19 daily, the Health Ministry said.
These were detected primarily through active surveillance testing, such as rostered routine testing (RRT), and aggressive tracing and testing.
About 2 per cent of these newly-detected cases had positive serological tests, indicating past infections, according to a report by The Straits Times.
Asked if some of the cases in the cleared dormitories had slipped through undetected by the polymerase chain reaction (PCR) tests, Tan said: "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 was 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," the minister was quoted as saying.
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 Tan, who cited studies showing that up to 30 per cent of infected individuals were 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," he said.