Weekly cases of hand, foot and mouth disease (HFMD) have hit a four-year high, but the predominant circulating strains this year are usually mild and no severe case has been reported so far.

There were 1,317 cases reported last week, from May 8 to last Saturday, figures from the Ministry of Health (MOH) show.

The last time weekly cases climbed above 1,300 was in 2012.

There are 15,579 cases so far this year, more than the 11,117 for the same period last year. Two childcare centres were required to close earlier this year, but none is currently closed because of HFMD.

Childcare centres and kindergartens may have to close for 10 days if more than 16 pupils, or 23 per cent of the enrolment, come down with HFMD over a period of more than 24 days.

So far, 49 kindergartens and childcare centres have been identified as having clusters of prolonged transmission this year. This refers to those with more than 10 cases, or more than 13 per cent of pupils getting HFMD, and with a transmission period of more than 16 days.

Such centres will be put on a watch list on the MOH website.

The three on the list now are Wesley Vineyard Childcare in Serangoon North, PCF Sparkletots Preschool @ Jurong Spring, and Catholic Kindergarten at Maris Stella High School.

Yesterday, MOH said that HFMD cases "are expected to increase from time to time". So far, no severe case or death due to HFMD has been reported this year.

Symptoms include fever, sore throat, rashes on the hands and feet and mouth ulcers. HFMD is a viral infection spread by contact with an infected person's bodily fluids.

While the effects of this virus are usually mild, there is a more serious strain called EV71 that can affect the nervous system in severe cases and cause swelling of the brain lining. This could result in death.

Housewife Alice Ho, 42, whose son attends Catholic Kinder- garten's afternoon session, said she was not too worried. She said the kindergarten, which runs two sessions, will issue a memo to parents when there is a new case.

It also teaches children to practise good hygiene habits like not putting their fingers in their mouths, she said, noting that the most recent case which worried her the most happened in the morning session. Catholic Kindergarten declined to comment.

A PAP Community Foundation (PCF) spokesman said there are currently fewer than 85 cases across all 374 PCF centres, and fewer than 10 cases of HFMD at each affected centre. The PCF said the number of cases is "starting to taper down" this month and PCF centres "strictly follow" prescribed hygiene practices.

Wesley Vineyard Childcare has seen around 14 cases of HFMD since last month.

A spokesman said all children who were ill have since recovered.

Earlier this month, MOH said it is working with partner agencies to step up preventive measures.

The Early Childhood Development Agency, Ministry of Education and People's Association have been asked to step up measures such as screenings.

To minimise the spread of HFMD, high standards of hygiene should be observed by children and adults, said MOH. Any child exhibiting HFMD symptoms should be kept away from school and crowded public places and be given medical attention early.

• Additional reporting by Aleysa John and Sabrina Faisal