INITIAL tests show a virus caused the illness that struck down 80 staff and pupils at a school.

The Grange School in Hartford was forced to shut on Friday after the sickness bug spread rapidly on Thursday, affecting more than 30 staff and around 50 pupils.

Environmental health inspectors have carried out tests on samples from three people from the school.

Dr Nick Phinn of Cheshire and Merseyside Health Protection Agency said the first sample showed a virus and he does not expect substantial differences from the other tests.

He added: 'In places like schools you can get rapid spread from person to person. We have a lot of cases of viral gastroenteritis especially in winter and spring but all it takes is one person to have it in the right conditions.'

All those suffering from the illness were told to stay at home until they were free of symptoms for 48 hours and detailed infection control advice was issued to all pupils.

By Monday, all but two affected staff had returned to work, and the number of new cases among pupils had diminished.

Pupils who went abroad on school trips last week have not shown any symptoms of the illness and the school term ends today.

A spokesman for Cheshire County Council said no other schools in the area have been affected.

Headteacher Christopher Jeffery said: 'The school was hit quite suddenly by the spread of this bug on Thursday morning, and procedures were put in place very promptly to do all we could to halt its spread.

'Our decision to close the school on Friday was endorsed by officers from Vale Royal Borough Council, and seems to have been instrumental in stopping the spread among staff and slowing it dramatically among pupils.

'It has been a particularly unpleasant illness for those who have suffered from it, but I am happy that, as a school, we did all we could to prevent its spread once the extent of the problem became clear.'