The European Centre for Disease Control (ECDC) has said that influenza cases are increasing "unusually early" in the EU this season.
It said the season has started about three to four weeks earlier than the two most recent seasons.
The centre has urged people for whom the flu vaccine is recommended to get vaccinated as soon as possible.
The ECDC said there is uncertainty regarding the public health impact of the upcoming influenza season.
However, it said the centre is preparing for the scenario that Europe could face a more severe season than previously, especially if there is low vaccine uptake.
It said that a newly emerged influenza strain A (H3N2) subclade K is driving the circulation.
The latest report from the Health Protection Surveillance Centre says influenza activity continued to increase across most surveillance indicators in Ireland but remains at low levels.
There were 637 influenza cases reported in the week to last Saturday.
