‘21-day quarantine for travellers from India will help Singapore detect more COVID-19 cases’

However, it is not yet necessary to ban flights from India, it said.

''A 14-day quarantine or SHN (stay home notice) would detect more than 98 per cent of COVID-19 cases, including those who were infected while on the plane,'' said Associate Professor Hsu Li Yang, the vice-dean of global health at the NUS Saw Swee Hock School of Public Health.

''A 21-day quarantine backed by specific tests would detect virtually all cases. However, that would impose a significant mental and financial cost'' to the traveller, Yang said.

Singapore announced new safety measures on Tuesday, including fewer approvals for foreigners who are not permanent residents and are coming in from India, which is experiencing a second wave believed to be fuelled by a variant with a double mutation.

All travellers from India must now isolate for seven days at a residence after spending 14 days at a dedicated facility for those serving SHN.

The new measures have come amid a recent rise in locally-transmitted cases and as a new three-person cluster here has just been linked to a 43-year-old Indian national who was ''probably reinfected'' in India.

The work pass holder, who was asymptomatic, had tested positive on arrival from India on April 2 but was discharged after a few days as he was considered no longer infectious. But he went on to infect his sister-in-law and her husband.

Associate Professor Alex Cook, vice-dean of research from the NUS Saw Swee Hock School of Public Health, said the positive swab result could mean that the Indian was infectious or had recently recovered from an infection.

A serology test to look for COVID-19 antibodies was then done and the man tested positive, meaning that he was infectious at least two weeks ago. But it is now clear that he could have been infected sometime back and then reinfected recently, and hence tested positive on both tests.

Cook said this shows that it's vital to assess the interpretation of the combination of a positive swab and serology tests, given that it can be a reinfection case, and continued vigilance is key.

India's surging outbreak has prompted places such as Hong Kong and New Zealand to ban flights. But the Singapore daily had experts saying that it is not yet necessary to ban flights from India or tighten guidelines on social and other gatherings.

Infectious disease expert Leong Hoe Nam said while banning flights is easy, it is about achieving a balance, as there's also the need to support the economy and be compassionate in allowing family members to come to visit.

Flight bans provide just short-term relief, said Professor Teo Yik Ying, dean of the NUS Saw Swee Hock School of Public Health.

''If such flight bans were successful, we would have seen a much smaller COVID-19 footprint globally, given the number of flight bans and border closures in the early months of 2020,'' he said.

''What I suspect ... is that these new variants that have emerged in one country are in fact already circulating in other countries,'' Teo said.

It's better to prevent virus variants from going on to seed uncontrollable community outbreaks with a comprehensive strategy that includes stricter border controls for travellers from India, he said.

''This, together with the repeated testing that will be applied to such travellers, will greatly increase our ability to reduce any leakage into the community, such as what we have seen last week,'' Teo said.

He added that the 14-day quarantine was never able to detect 100 per cent of the cases. ''We know from the epidemiological data that there are people whose incubation period actually extends beyond 14 days, just that the chance of this happening is low,'' he said.

Meanwhile, 11 workers tested positive for COVID-19 at Westlite Woodlands dormitory on Wednesday -- the largest number of infections in the foreign worker dormitories in months.

A letter from Westlite Woodlands to its clients said that 11 of the residents at the dormitory were confirmed to have tested positive for COVID-19 as of Wednesday morning, reported the Channel News Asia (CNA), adding it has seen the letter.

The results are from 568 tests carried out on Tuesday for residents from levels two to seven of Block A of the dormitory, located at 2 Woodlands Sector 2.

According to the letter dated April 21, all the block residents, which number more than 1,100, will be sent to a government quarantine facility (GQF) for 14 days as a ''precautionary measure''.

Swab tests will also be conducted on all the remaining residents in Block B of the dormitory, it said.

The 11 dormitory cases did not appear in the Ministry of Health's case count on Wednesday, which said there was one new community COVID-19 infection and 14 imported cases.

One of the infected workers is the roommate of a worker who tested positive on Apr 19, said the Ministry of Manpower in a press release on Wednesday night.

As a close contact of the infected worker, he had already been quarantined.

There have been more than 54,000 COVID-19 cases detected in foreign worker dormitories since the start of the pandemic last year.

Although the numbers peaked in the middle of last year, cases in the dormitories have fallen dramatically and before Wednesday, there were only seven cases reported since Janary 1 this year.

As of Wednesday, Singapore has reported a total of 60,880 COVID-19 cases and 30 fatalities from the disease.

As of Tuesday, 60,540 have fully recovered from the infection and have been discharged from hospitals or community care facilities. There are currently 74 confirmed cases who are still in hospital including one in critical condition in the intensive care unit while 221 are isolated and cared for at community facilities for mild symptoms, or are clinically well but still test positive for COVID-19.