NPHET is to advise the government whether cities could be placed on higher COVID restrictions instead of locking down entire counties.
It comes amid concerns about Waterford, Cork, Limerick and Galway, as cases in all four cities continue to rise.
Donegal will enter level three restrictions from midnight and the Taoiseach has said health officials will be working with their counterparts in the north to ensure a synchronised response both sides of the border.
Micheál Martin also says NPHET will be examining whether cities could be treated differently to the rest of the county they're in.
"NPHET will advise us in terms of any restrictions that may have to come in for other areas.
"They are concerned about urban centres...particularly as Universities and Institutes of Technologies re-open in the coming weeks.
"That is a concern, where you have high-density populations. The virus can thrive in those situations."
