Swine flu is among several strains of influenza to have hit Leicestershire schools.

Hundreds of children have been forced to stay at home after suffering high temperatures, vomiting and breathing problems.

But health officials say parents should not be worried and are advising them to keep their children off school if they feel unwell to avoid spreading germs.

Head teachers have also received advice from the Health Protection Agency (HPA), including making sure children wash their hands regularly.

Dr Philip Monk, from the HPA, said: "We ask head teachers to contact us if large numbers are ill.

"We've been into two city schools and a county school as a matter of course to take swabs so we know there are four different strains causing problems.

"This is a bad winter as far as respiratory viruses are concerned.

"Whereas we vaccinated against swine flu during the pandemic last year, that was the only viral infection we were dealing with.

"There's no point vaccinating now as it wouldn't tackle all the strains out there.

"It's difficult to say what's causing it. Colder weather tends to cause a drier atmosphere and that can aid transmission."

Christ Church and St Peters Church of England Primary School, in Loughborough, had more than 100 of its 411 pupils off sick in one day last week because of flu.

Head teacher Sandy Gourlay said: "We've had a lot of children off ill but are returning to normal levels.

"Some staff have also been off but we've carried on and our nativity is still going ahead over the next few days.

"Advice from the HPA was very helpful."

Woodland Grange Primary, in Oadby, had up to 60 children off in one day out of 364 pupils.

Head teacher Kirk Hayles said: "It's quite unusual to have so many children off ill but sometimes one year is worse than others.

"Parents have responded well to requests to keep children at home if possible."

St Thomas More Catholic Primary, in Knighton, Leicester, had 66 children out of 282 off ill last week.

GPs' surgeries and chemists have reported a rise in patient numbers over the last two weeks and say they are happy to give advice to worried parents.

Dr Andy Ward, from South Wigston Health Centre, said: "We've seen a big increase since Friday when we saw about 90 patients between four doctors.

"A lot of children have come in with respiratory influenza viruses with high temperatures and, in some cases, vomiting.

"Any child that's still eating and drinking normally should be fine, but for those who aren't Paracetamol and Calpol will help bring temperatures down and it's important to make sure they have fluids.

"Anyone with a persistent temperature and vomiting should go and see a doctor or call NHS Direct out of hours."