The acting Chief Medical Officer revealed tonight that one restaurant in Cork was the starting point of a cluster that has caused 57 Covid cases so far.
Speaking to RTÉ News Dr Ronan Glynn said: "We have one cluster, for example, tonight in Cork, from a café restaurant where a number of people from different households socialised.
"At the moment, that cluster is at 57 cases. We have to cut down the size of these clusters, we have to cut down socialisation if we are going to get on top of this disease."
Earlier, the Department of Health has been notified of 442 new cases of Covid-19 and four further deaths.
There has now been a total of 1,806 coronavirus-related deaths in Ireland and 36,597 cases.
There were 170 cases confirmed in Dublin, 47 in Cork and 28 in Donegal.
The remaining breakdown of cases is as follows:
- 23 in Meath;
- 21 in Galway;
- 20 in Monaghan;
- 14 in Clare;
- 12 in Roscommon;
- 11 in Laois and Longford;
- 10 in Cavan, Limerick and Tipperary;
- 9 in Kildare;
- 8 in Wicklow;
- 5 in Louth and Wexford;
- and the remaining 28 cases in 9 counties.
Of today's confirmed cases, 67% are under 45 years of age.
There was also 69 cases identified as community transmission, with 54% of today's cases associated with outbreaks or close contacts.
Meanwhile, no counties will be moved up a level of restrictions today after a decision from NPHET.
However, there will be further nationwide restrictions on visitors to people's homes.
The rules are to change meaning people can have no more than six people from one other household in their home at any one time.
It is in a bid to reduce community transmission caused by gatherings in houses and apartments.
The Department of Health's Chief Medical Officer Dr Tony Holohan will return to his post next week.
Dr Holohan stepped back from his role in July to spend time with his family as his wife was receiving palliative care.
Health Minister Stephen Donnelly says he's looking forward to working with the returning CMO.
Another 259 people have tested positive for coronavirus in Northern Ireland, the Department of Health said.
It brings the tally of infections to 11,952.
Almost 2,000 have been diagnosed in the last seven days.
Two more deaths were reported.