Weddings, hen parties and communions have contributed to increased demand for Covid tests, according to the HSE.
About 100,000 tests were done over the past week — with a notable spike in the past five days.
There were 11 per cent more tests on Saturday than the previous Saturday.
The HSE's head of testing and tracing, Niamh O'Beirne, said there is no obvious reason for the spike.
“Generally speaking increased social mixing, different events between parties, communions, we've heard some of those events have large numbers of close contacts — weddings, hen parties and communions in particular — the only age group where it's not growing is the 15-24s and the 25-34s. All other age groups are seeing an increase in the number of positive cases and the number of tests.”
A further 1,358 Covid-19 cases were confirmed in the State on Monday.
It comes as the chief executive of the HSE Paul Reid has warned it is going to be a “very challenging” winter for the health service.
Speaking on Newstalk Breakfast, Mr Reid outlined the current situation with Covid-19 figures after it was confirmed there were 393 being with the virus in hospital on Sunday night, 74 of whom were in intensive care units, a rise of 23 per cent.
In the last four days the number of cases has increased from 1,500 to 2,000 per day, Mr Reid added. Of the 74 patients in intensive care, 67 per cent were unvaccinated and three per cent were partially vaccinated, he said.