Ireland has the fourth highest incidence rate of Covid-19 in the EU - with only Cyprus, Portugal and Spain faring worse.
The Republic's 14-day rate is 121 per 100,000 people, with 534 new cases confirmed yesterday.
627 new cases were reported in the North yesterday - the highest since late January.
Donegal GP Denis McCauley, from the Irish Medical Organisation, fears the Republic's rate could increase six-fold in the coming weeks.
"Northern Ireland is a case study for the Republic of Ireland, they have had numbers which have gone up by a factor of 6 in the last number of weeks.
"This is because of the Delta variant, in a situation where there is indoor hospitality.
"In the Republic of Ireland we have to anticipate that there is going to be an increase in numbers, that increase if it's in the same magnitude could mean we have several thousand positive cases per day."
