The Health Service Executive said it believed the flu season has hit its peak over the Christmas and New Year period - six weeks earlier than in recent years.
Speaking on RTÉ's News at One, HSE Assistant National Director for Public Health Dr Kevin Kelleher said however that it is expected the flu will be around for another four to five weeks.
Figures released at a briefing for the Government's Winter Plan today shows a significant increase in the number of people over 75 who attended hospital in the week leading up to Christmas Eve.
There was an increase of 25% compared to the same week last year.
The figures also show there were 867 cases of the flu, which was a decrease from the 1,005 notified cases the previous week.
Speaking at the briefing, Minister for Health Simon Harris said there was a reduction in the number of attendances and admissions to hospital in the week running up to Christmas but the numbers were still significantly higher than the same period last year.
Dr Kelleher said there was still time for people to get the flu vaccination and that so far this flu season, 19 people have died as a result of the virus.