Three-quarters of the 40 cases of Covid-19 confirmed in the Republic yesterday involved people under the age of 45.
It was the highest number of cases in six weeks, bringing the total number to 25,929.
But no new deaths were recorded, meaning the death toll remains at 1,764.
Sligo is one of five counties reporting new cases of Covid-19.
One new case has been identified in the county, bringing the total to 149. It comes a day after Mayo reported a new case, bringing its total to 576.