A stomach bug which affected nearly two hundred people at a primary school in Lampeter is believed to be Norovirus.
Around 180 pupils and 16 staff at Ysgol Gynradd Ffynnonbedr were affected by vomiting and diarrhoea this month.
Public Health Wales say they are 'optimistic that the outbreak is coming to an end'.
Dr Jörg Hoffmann, Consultant in Communicable Disease Control for Public Health Wales, said: “We are very grateful to staff and parents at the school who have co-operated so readily with the investigation.
“As well as issuing sample pots to children, we also issued questionnaires to gather information on where pupils had been and what they had eaten before becoming unwell, and received more than 330 responses.
“These, together with microbiological sampling and environmental sampling, have led us to believe that the cause of the outbreak is Norovirus.
“We are hopeful that there will be no further cases following the Easter holidays.”
Norovirus causes vomiting and diarrhoea and is easily transmitted from person-to-person.
Anyone experiencing symptoms should contact their GP or NHS Direct on 0845 46 47, and is advised not to return to school or work until they have been symptom-free for 48 hours.