The Department of Health's chief medical officer is undergoing tests in hospital.
Dr Tony Holohan has told RTÉ it's not related to Covid-19 and he's expected to be released tomorrow.
He told the broadcaster that he is in good spirits.
He was seen clutching his chest by social media users during the briefing, which is streamed online.
He went to St James’s Hospital in Dublin for tests and is expected to be released on Thursday.
Dr Holohan has been giving daily updates to the media on the situation regarding the outbreak since it began last month.
His deputy, Professor Ronan Glynn, will take over in his absence.