A WEST Devon primary school was forced to close early for half term last week, due to an outbreak of a virulent sickness bug which spread through the classrooms like wildfire. The headteacher of North Tawton Primary School, Nick D'Agorne, took the decision to close on Thursday evening after 20% of children became ill with the Norovirus bug. Mr D'Agorne said: 'It's a projectile vomiting virus — the poor children are just sitting there and don't know it's about to happen, and because it's quite violent, it frightens them. 'This morning (Thursday) we had three or four off and by the end of the day it was 28, which represents 20% of the school.' 'We've been advised that one bout of vomiting contains in excess of 30 million viral particles — but you only need between ten and 100 particles to catch the bug, so it's very contagious.' Mr D'Agorne said the youngest children in the school had been affected most badly by virus, which could also cause diarrhoea. Mr D'Agorne said the school would be 'deep cleaned' during half term — staff were advised to work from home last Friday. It is hoped that with a week away from school and the cleaning process, the bug could be eliminated. Children should not go back to school until 48 hours after the last period of vomiting and parents have been advised that good hygiene is the best way to stop the virus spreading. The sickness bug is not the only problem affecting the school — children have also been suffering from an outbreak of 'slap cheek'. 'When it first appears it looks as though you have been slapped in the face — it's a rash which then goes to other parts of the body, and it's very itchy,' said Mr D'Agorne. 'The trouble is, it's contagious before it appears — a lot of children have been off with that,' said Mr D'Agorne.