Doctors in the UK have warned that it could be the worst outbreak of the bug in 50 years, as official figures revealed cases more than doubled in just one week.
Government statistics show 1,111 people were struck down with flu as temperatures dropped last week - a 156 per cent jump on the previous seven days. Although the number of flu-related deaths recorded in Ireland so far is under ten, 73 people have been hospitalised and the Irish Health Service Executive is urging people to get vaccinated.
In a statement, the executive said the number of reported cases of flu had increased in the week before Christmas and that flu 'is now actively circulating in Ireland'.
Director of the HSE's Health Protection Surveillance Centre Dr Kevin Kelleher told RTE the executive has been informed of a 'small number of deaths directly related to influenza (less than ten)' in the last two weeks.
The executive is urging people, particularly those in high-risk groups, to make sure they are vaccinated.
These include people aged 65 and over; anyone with a chronic illness; all pregnant women as well as people in care homes or long stay facilities.
Meanwhile, figures released by Public Health England show a sharp rise in cases, triggered by a surge in two aggressive subtypes attacking the population simultaneously. The H3N2 subtype triggered two and a half times the normal number of cases in Australia. Britain's flu season tends to mirror what has happened there.
Experts fear the virulent flu strain, which has now reached the UK, could prove as deadly as the Hong Kong flu in 1968, which killed one million people.
Usually, just one subtype, either influenza A or B, is responsible for the majority of cases. It spreads much easier in the cold weather.
But last week 522 cases of influenza A and 546 of influenza B were recorded across England and Wales. Some 43 cases are yet to be identified.
However, this winter's outbreak shows no signs of slowing down, as flu cases are expected to rocket even further in the coming weeks.
However, this winter's outbreak shows no signs of slowing down, as flu cases are expected to rocket even further in the coming weeks.
Cases this year are almost 10 times higher than they were at the same point in 2015, according to the PHE data. Just 132 cases were recorded then.
But in 2015, Government figures suggested that the winter flu played a part in more than 16,000 deaths. Only 577 deaths were recorded in the previous winter.
The total recorded in week 51 is also double that of last year, when 583 cases, mainly of the H3N2 subtype, were reported.
The sharp rise in flu is only expected to cause further problems for the NHS, with cases of the winter vomiting bug also continuing to soar.