More than 100 pupils were absent from classrooms after a sickness bug swept through a market town school.

Children at St Nicholas Junior School in Dereham were struck down with what is suspected to be norovirus on yesterday.

It saw more than 100 youngsters - a quarter of the school - absent that day or sent home.

All pupils affected were advised not to return to school for 48 hours which meant that, together with more children taken ill or kept at home by their parents, 150 youngsters were not in lessons today.

The cause of the sickness bug, which had caused diarrhoea, vomiting, nausea, fever and headache, is not known, and it affected mainly those in Year 4, aged eight and nine. Members of staff have also been unwell with the virus.

It is believed to have affected those who have school dinners and packed lunches equally.

Headteacher Neil Toplis said the decision to keep the school open was taken on the advice of Public Health England and that the school had undergone a 'significant advanced clean' on Thursday evening.

He said: 'We've taken advice from the health protection team and have put a cleaning regime in place.

'There is no common pattern about it, there is a mixture of people who have had packed lunches and school dinners.

'It's a fairly virulent bug and it's really quite unusual to have that many children off school at once.'

Norovirus, also known as winter vomiting disease, causes gastroenteritis and is highly infectious.

The virus is easily transmitted through contact with infected individuals from one person to another.

Outbreaks are said to be common in semi-enclosed environments such as schools and the virus normally lasts for up to two days.

Dr Hamid Maghoub, consultant in communicable disease control for public health England in Norfolk, said: 'The identity of the infection has yet to be confirmed but the symptoms of the young people and adults who became unwell, which include diarrhoea and vomiting, would suggest that it is norovirus.

'People usually recover fully within two to three days with plenty of rest and replacing fluids that they will have lost through the main symptoms of this illness.'

Have you got a health story for the EDP? Email health correspondent Adam Gretton at adam.gretton@archant.co.uk