Ireland's COVID-19 death toll has reached 5,000, with two further fatalities reported on Thursday.
Some 448 new cases have also been confirmed.
Donegal has the highest 14-day incidence rate in the country, at 250 cases per 100,000 people.
But Deputy Chief Medical Officer, Dr Ronan Glynn, has expressed particular concern about the situation in Dublin.
"We have some concerns in particular about Dublin, while its incidence is not the highest in the country... incidence has taken off there versus the rest of the country over the past number of days.
"And obviously, given the population size in Dublin, if that continues it will drive the national picture.
"We are aware, over the past number of weeks, that Delta was present at a greater proportion in the Dublin area."
The country's reproduction number has risen above one, according to Professor Philip Nolan from NPHET.
"The situation analysis is incidence is increasing, and that's a real concern.
"We're at close to 390 cases per day now, and above 100 cases per 100,000 population over 14 days.
"Growth rate at 2% per day, and the estimate of reproduction number is that it is now above one - estimated between 1 and 1.2 - and that incidence we're seeing across all age groups.
"This is cause for concern".