Managers are being advised to roster back-up staff because of the number of people who will have to self-isolate in the days and weeks ahead.
75,000 people have tested positive for Covid-19 in the last ten days alone.
But with close contacts of people infected with the Omicron variant asked to isolate too, it could be a quarter of a million or more.
Infectious diseases consultant Professor Sam McConkey of the RCSI says management need to make contingency plans:
"There will be a very significant chunk of the population isolating. So as I've said, about 10 days to 14 days ago, the biggest issue for businesses and for public sector organisations, like the hospitals where many of us work, is actually keeping enough staff, who are not sick and are not having Omicron to keep the show on the road."