Another seven preschools and six childcare centres were also asked to voluntarily close their doors, said the ministry yesterday.

The 10-day closures come as the number of HFMD patients, predominantly young children, continues to rise.

Almost 1,250 people caught the disease last week, a 25 per cent jump over the preceding seven days. Of these, 16 were children who had to be hospitalised, most because they were not eating well.

HFMD is a common childhood ailment that causes ulcers, rashes and blisters. Symptoms are usually relatively mild, however.

The new cases brought the total number of confirmed cases since the beginning of this year to 7,560.

Given the rise in HFMD cases and the re-emergence of the potentially deadly EV71 strain, a spokesman said the ministry was lowering its threshold for closing schools.

The change is a bid to prevent the virus, which is transmitted through saliva, blister fluid and faeces among other things, from gaining more ground.

Health officials said the closures will give infected children a chance to recuperate at home and hopefully stop the spread of the disease.

They will also give schools and childcare centres time to disinfect their toys and thoroughly clean their premises.

Two of the 20 centres that face closure are located within public hospitals. One, Learning Vision@Work located in KK Women's and Children's Hospital (KKH), was ordered to shut.

Senior operations manager Marini Khamis said: 'We will take this opportunity to thoroughly disinfect all the toys, equipment and furniture.'

Not all schools, though, are embracing the MOH decision. Ramakrishna Mission Sarada kindergarten at Bartley Road has been ordered to shut after 14 of its 510 preschoolers came down with HFMD this month.

But the centre's manager, Swami Satyalokananda, wants to appeal against the closure. He said the situation at the school is getting better.

The last time schools were closed because of HFMD was in 2006 when a centre in Jurong was ordered to shut after 27 per cent of its students fell ill over 21 days.

Schools were also shuttered in October 2000. That decision affected about 140,000 children and their parents. Seven children under five ultimately died after being infected by the EV71 strain, which can lead to complications such as infections of the brain, heart and lungs.

This time round only one child has been seriously affected. A seven-year-old girl suffered a severe case of HFMD that resulted in the swelling of her brain. Her condition has since improved.

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