A Witney school alerted several hundred parents after a pupil was rushed to hospital with meningitis.
Rod Walker, headteacher of Henry Box School, sent out letters to the families of all Year 7 students within a day of the boy falling sick.
The 12-year-old pupil was treated with antibiotics and returned to school on Monday, a week after being taken to the John Radcliffe Hospital, Oxford. No other pupil has shown symptoms of the potentially lethal virus.
Mr Walker said yesterday: "It was a scare. Within 48 hours the lad's parents contacted me to say he was OK."
The precautionary alert followed guidelines set out by Oxfordshire's community physician Dr Dick Mayon- White.
Parents were told not to panic because the virus is rarely infectious outside the immediate family.
The scare came a month after three children from the same family were struck down.
Charlotte Harrop, two, of Thorney Leys, Witney, her baby brother Fletcher, and their cousin Bradley Horne, of James Wolfe Road, east Oxford, all had the virus.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article