As a small country that is not resource-rich, Singapore cannot afford to shut its borders for a long time, said Education Minister Lawrence Wong yesterday.
Mr Wong, who co-chairs the multi-ministry task force on Covid-19, was explaining why Singapore did not close its borders to India earlier, given the raging outbreak there.
Singapore stopped entry to all long-term pass holders and short-term visitors with recent travel history to India within the past fortnight from April 24.
"We are small… We need migrant workers to build our homes," he said. Foreign workers are also needed for other essential services, including caring for the elderly.
"It's really very hard for us to close our borders permanently," he said. "Instead, we've always taken a risk-based approach in managing our borders from the start."
This involves controlling the number of arrivals. He said the overall number coming in has been going down, even before curbs on arrivals from India kicked in.
"We've already become very tight, to the point that the backlog of applications has been growing… Many projects have been suffering from delays, as all of us know."
He added: "Some of our housing projects may now be delayed by up to a year or more.
"So it does come at a considerable cost to Singaporeans."
Migrant workers who come in are isolated and "we've been progressively tightening that regime over the past few months". They are also tested more regularly.
In spite of all measures, Mr Wong said there will be leaks into the community from time to time.
This can happen even in a country like China with its very tight border measures, he added.
So there cannot be sole reliance on border measures, he said.
"We have to make use of other tools at our disposal," he said.
"If we do all of these well, then we can control the spread of the infection in our community."
As for visitors who tested negative, but later test positive when they want to leave the country, Mr Wong said there are two possibilities. One is they could have been infected in the community while in Singapore.
The other is that the cases involve an older infection and they are "intermittent shedders" of virus particles. If so, they are less likely to be infectious.