SINGAPORE - There were 23 new coronavirus cases confirmed as at Sunday noon (April 18), taking Singapore's total to 60,831.

They included 22 imported cases who had been placed on stay-home notice or isolated on arrival in Singapore, said the Ministry of Health (MOH).

There was also one community case.

No new cases were reported within migrant workers' dormitories.

More details will be announced on Sunday night.

On Saturday, four new cases of locally transmitted Covid-19 infection were reported, one of which involved a national serviceman who was due to attend his in-camp training (ICT) at Nee Soon Camp.

Two of the new cases are linked to a National University of Singapore (NUS) senior research fellow from India who was confirmed to have Covid-19 on Thursday. On Saturday, MOH said his colleague - a 31-year-old Swiss woman who is also a senior research fellow at NUS - had caught the virus too.

She had interacted with him on April 12 and developed a sore throat on April 15 but did not seek medical treatment. As she had been identified as a close contact, she was placed on quarantine.

Her test came back positive on April 16.

The man's 35-year-old brother, who works at DBS Bank at 2 Changi Business Park Crescent, was also infected. He had been working mostly from home, and last went back to his workplace between April 6 and 9.

As he had also been identified as a close contact, he was placed on home quarantine on April 15.

He developed a fever the next day and was taken to the National Centre for Infectious Diseases (NCID) after he informed MOH of his symptoms. His test came back positive on April 17.

Another case reported on Saturday was that of a Singaporean man, 35, who works as a freelance photographer. He was tested on April 15 as part of the Singapore Armed Forces' protocol to test national servicemen at the start of their in-camp training.

His pooled test came back positive, and a swab done on April 16 gave the same result. He was taken to the NCID, where he developed a fever on the same day.

MOH said his serological test result has come back positive, which is indicative of a past infection.

A Ministry of Defence spokesman said immediate and thorough disinfection of the premises that the serviceman had been in was carried out.

All personnel identified as close contacts during the ICT were also swab tested. None tested positive and all are under quarantine.

"They will be monitored and retested to confirm their negative status before they are released from quarantine," the spokesman added.

The fourth patient is a female Singapore permanent resident, 41. She is an accountant at OM Universal at 11 Kaki Bukit Road 1 but had not gone to the office since she developed a cough on the evening of April 14 after work.

She went to a clinic the next day, where she was tested for Covid-19. The result came back positive on April 16 and she was taken to NCID.

One of her household contacts is a work pass holder who arrived from India on April 2, and had tested positive for Covid-19 on that day. But he was later assessed to be a recovered case, based on his serology result on April 4.

There were also 35 imported cases on Saturday.

All 35 had already been placed on stay-home notice upon arrival in Singapore.

Overall, the number of new cases in the community has increased from two in the week before to seven in the past week.

The number of unlinked cases in the community has also increased - from two in the week before to four in the past week.

With 17 cases discharged on Saturday, 60,448 patients have fully recovered from the disease.

A total of 62 patients remained in hospital on Saturday, including two in the intensive care unit, while 253 were recuperating in community facilities.

Singapore has had 30 deaths from Covid-19 complications, while 15 who tested positive have died of other causes.

Globally, the virus outbreak, which began in December 2019, has infected more than 140 million people. More than 3.01 million people have died.