Instances of flu and respiratory illness are on the rise, according to HSE Chief Executive Bernard Gloster.
Mr Gloster said that in the "week up to last Friday night" there were 1,845 cases under the categories of Covid, RSV and Flu.
He added that flu accounts for just under 1,000 of those.
"Over the past four weeks, influenza particularly followed by RSV and Covid are somewhat stable, but influenza has been doubling," Mr Gloster said
This doubling effect, he said, "obviously means that a lot of people are looking for assistance on top of the non-flu cases that will attend at our emergency departments, so it is quite significant".
He said in the past week things have taken a turn, with over 4,600 people over the age of 75 years old attending emergency departments.
"That's the highest this year in that age category," he said.
Speaking on RTÉ’s News at One, the HSE chief said demand is high in hospitals and the situation this year will be pressurised.
"The next two weeks particularly look quite concerning in respect of the prevalence of flu," he said.
But Mr Gloster said significant measures are in place across the system to cope with the situation in the coming weeks.
He said the HSE was focused on areas, including hospital avoidance through self-care advice.
He added that there will be an increase in available GP practices from the 27 December, with extended days and additional out-of-hours services.
"We are also putting into our out-of-hours GP service, what is the equivalent of 150 extra doctors operating in four-hour sessions," he said.
In hospitals, Mr Gloster said the focus is on the care and management of people in emergency departments.
From next week and into three weeks of January, he said "schedule care work" likely will not be planned unless it is time critical work.
"The focus is very much on emergency care, the focus is on caring for people outside of the hospital when they can be and the focus is also on the decision-making over the seven days of the week in the hospital to keep the hospital system moving," he said.
