SINGAPORE - Singapore confirmed 73 new coronavirus cases on Wednesday (March 25) - the largest increase in a day, which brought the total number of cases here to 631, the Ministry of Health (MOH) said.

Two new clusters have formed - the first has 18 cases linked to a new cluster at the PCF Sparkletots pre-school at Fengshan Block 126. Of these, 14 cases are staff at the pre-school, while four are family members of case 601 - a 47-year-old Singaporean woman.

The second new cluster comprises three staff members at Dover Court International School.

In a statement, an Early Childhood Development Agency (ECDA) spokesman said PCF will close all of its centres for four days from Thursday to Sunday, to review its precautionary measures and clean and disinfect all its premises.

The spokesman said another 13 staff members from the Fengshan pre-school - a mix of teaching and non-teaching staff - tested positive for Covid-19 on Wednesday, following the Nursery 2 teacher who was found to have the coronavirus on Monday.

One of them is the centre principal, who was well when she was at work on March 17, but developed symptoms in the afternoon, the spokesman said.

On that day, she had a meeting with her staff, and later attended a course with other pre-school staff in the evening. The principal saw a doctor the next morning, on March 18, and was on medical leave until last Friday.

Most of the other staff who tested positive began developing symptoms from last Friday and over the weekend, the spokesman said.

Of the 73 new cases, 38 were imported. All except one of the imported cases were returning residents and long-term pass holders who had travelled to Europe, North America, Asean and other parts of Asia.

The remaining 35 new cases were locally transmitted. Of these, 27 cases were linked to clusters or previous cases, while contact tracing is ongoing for eight cases that are not linked to travel or previous cases, the MOH said.

Five more cases were discharged from hospital. To date, 160 patients fully recovered from the infection and have been discharged.

Among the 404 patients still in hospital, a total of 17 are in critical condition in the intensive care unit.

"Sixty-five cases who are clinically well but still test positive for Covid-19 have been transferred to Concord International Hospital, Mount Elizabeth Hospital and the Community Isolation Facility at D’Resort NTUC for isolation and care," the ministry said.

As of noon on Wednesday, the MOH had identified 8,930 close contacts who have been quarantined. Of these, 2,643 are currently quarantined while 6,287 have completed their quarantine.

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Health Minister Gan Kim Yong on Wednesday told the House that the number of coronavirus cases will continue to rise in coming weeks as some of the 200,000 overseas Singaporeans return home.

He noted that the number of cases in Singapore had more than doubled last week.

Singapore announced its strictest measures to date in the fight against Covid-19 a day earlier, which included closing all entertainment outlets, limiting gatherings outside work and school to 10 people or fewer, and suspending all centre-based tuition and enrichment classes.

To deter people from travelling overseas, any Singapore resident or long-term pass holder who leaves Singapore from Friday will be charged unsubsidised rates should they be hospitalised in public hospitals for Covid-19 treatment.

They will also not be able to claim from MediShield Life or Integrated Shield Plans for these treatments at public and private hospitals.

The tough measures will take effect on 11.59pm on Thursday and will be in place until the end of April, at least.

To assist businesses and Singaporeans in coping with the economic impact of the outbreak, Deputy Prime Minister Heng Swee Keat will present a supplementary Budget in Parliament on Thursday. It will detail additional support measures for workers, businesses and households.

The coronavirus has so far infected more than 436,000 people worldwide and killed over 19,600.