This includes checking each child as he arrives for tell tale signs like mouth ulcers or little red blisters, and taking their temperatures two to three times a day.

Parents of a child suspected to have the disease will have to take the pupil home, and he can only return after he has been certified infection-free by a doctor.

Although clusters have been reported at some childcare centers, pre-school centres and primary schools, the Ministry of Health said none has been asked to close its doors.

The disease, which is transmitted through bodily fluids like saliva, is endemic in Singapore and outbreaks occur regularly. It affects mostly very young children, although adults can catch the virus.

It causes fever, sore throat, sores and ulcers in the mouth, and rashes on the palms, soles and buttocks. There is no medcine or vaccine for the disease. It is usually a mild disease, but complications can occur, and very rarely, death.

The enterovirus, which causes the disease, has been particularly active this year, infecting 50 per cent more people than in 2007. So far, 3,721 people have caught the virus this year, up from 2,480 for the same period last year.

The ministry's latest weekly bulletin reported that 585 people came down with the virus last week, up from 409 the previous week.

The increase coincides with the re-opening of school after the week-long March break.

The last time the weekly infection was this high was during the seven-week outbreak in May and June last year.