Influenza and respiratory illnesses have almost doubled across the country over the past two weeks.
The Health Service Executive is warning that the rate is expected to increase even further in the coming weeks.
It is urging people who are at-risk who have not been vaccinated to do so at their local doctors or pharmacist.
There has been several outbreaks of influenza-like illnesses in residential care facilities and in acute hospital settings throughout the country, particularly in Dublin.
The predominant flu strain is AH3 which is affecting mostly older people.