People could be putting their own communities at risk by travelling to holiday resorts abroad, according to the former head of the HSE.
Tony O'Brien says travelling abroad to visit a relative or loved one is a "completely different" thing to going to a holiday resort.
He was speaking as Chief Medical Officer Dr Tony Holohan urged people to reconsider any summer holidays they have booked.
Mr O'Brien told Lunchtime Live he himself made a short trip to the London area a few weeks ago to see his mother who had been very ill - and he's been self-isolating since he returned.
He explained: "I'm on day ten or day eleven of not having left the house, having driven myself home from the airport.
"I would draw a distinction between that and what we're now seeing, is the emergence of people thinking it's OK to go off on holiday... I myself have cancelled a long-standing plan for a holiday on one of the Canary Islands.
"Point-to-point travel... is completely different thing to going to places where thousands of people from dozens of countries are going to congregate. It's in the nature of holiday resorts that social distancing barriers tend to fall in those places.
"If you have a melting plot of people from lots of different countries with lots of different scenarios COVID... obviously if we return to the country and don't follow proper self-isolation, we're putting our communities at risk, and that could roll back all of the progress we've made in these very difficult last few months."
He also suggested it's very hard to maintain discipline people have shown in recent weeks when they're away on holidays.
Mr O'Brien said it makes sense that there would be 'green list' countries where people can travel for business or to visit relatives or partners, once the COVID situation is under control both here and in the other country.
However, he noted: "It's likely those things will change over time - if while you're away that country suffers an upsurge in COVID, you might still have to quarantine when you come back.
"As long as the Department of Foreign Affairs is saying that a particular country is a place you shouldn't go to except for essential reasons, then you shouldn't go there.
"If we can identify certain places where it is safe to travel to and back from where you don't need a self-isolation... the counter-point could be that if you're going to other places you may need to have a mandatory quarantine when you get back."
The former HSE chief did stress that Ireland can't cut itself from the entire world because some countries are unsafe to go to, especially as more countries open up their borders to each other.
He said: "What we can't do is fail to deal with the need to rebuild our economy... which of course is how we pay for all our public services and get people back to work. There is a balance to be struck."
However, Mr O'Brien said he'd feel "very, very foolish" to travel abroad against official advice and then get into difficulties abroad without travel insurance cover.
He said coming home and becoming a source of COVID-19 in his community would be the "worst possible outcome".