Health experts have warned cases of the winter vomiting virus could rise this week as offices and schools fully reopen after the festive break.

Five more wards in Scottish hospitals were closed to new admissions yesterday, bringing the total number affected by the norovirus bug to 24 north of the border.

Businesses and schools were told to brace themselves to cope with staff and pupils catching the virus.

The highly-contagious bug typically causes 48 hours of severe vomiting, diarrhoea and flu-like symptoms. Although sufferers quickly recover, it can be passed to others up to two days after symptoms clear.

Doctors estimate that more than 100,000 people a week are catching the bug across the UK and more than 100 hospital wards have been closed after patients contracted the virus.

New cases forced health chiefs in Chalmers Hospital in Banff, Ailsa Hospital in Ayr, Wishaw General and Glasgow's Western Infirmary and Gartnavel, to shut wards, adding to the 19 that are already closed to new patients across Scotland.

As Scots head to work and school this week, experts warned more will fall victim to the illness.

Hugh Pennington, professor of Bacteriology at Aberdeen University, said: "It is at its most serious in hospitals, where people are confined all the time, but the fact that everyone is heading back to work this week will give it a new head of steam."

Dr Steve Field, the chairman of the Royal College of General Practitioners, said: "People are at home with it over the holiday, which is the best place for them. Then next week the schools go back and you get a child outbreak and the children go home and give it to their parents."

Teaching unions are concerned about the effect that virus could have on schools. Ronnie Smith, the general secretary of the EIS, Scotland's largest teaching union, said: "If it spreads to children on any scale then it could impact on schools in that there might not be enough teachers for all the classes.

"This could also affect children who are preparing for exams, many schools have prelims at this time and have tests which form part of the assessments for their eventual grade."

Industry chiefs warned businesses to prepare. A spokesman for CBI Scotland said: "This is an issue that businesses are aware of and that does cause concern. Businesses will find that they will have to cover for staff who catch the bug."