Two teenagers, both pupils at St Nathy's College, Ballaghaderreen, Co Roscommon, are in hospital with meningitis.
Five doctors visited the school yesterday to give antibiotics to all 500 pupils at the school as well as to the families of the two teenagers.
The two, a boy and a girl, are suffering from meningococcal group C, and doctors are administering a specific vaccine against this form of the disease. Both of the teenagers are said to be in a comfortable condition, the boy at Sligo General Hospital and the girl at Mayo General Hospital.
The Western Health Board warned people to be vigilant for the symptoms of meningitis, which are drowsiness, irritability, vomiting, diarrhoea, fever, neck stiffness, widespread rash and headache.