Hospitals are being urged to curtail all non-emergency activity and introduce greater measures to reduce transmission of Covid-19.
It comes as the number of staff absent increases due to high infection rates.
The Irish Nurses and Midwives Organisation says the hospital system's too small to cope with servicing emergency care, Covid care and elective treatments.
General Secretary, Phil Ní Sheaghdha says staff are reaching breaking point:
"We now have a very exhausted workforce who are facing into their fifth wave. And what they're saying very clearly is, and what their Nurse Managers are saying to us very clearly is the level of goodwill, the level of just positivity that has been demonstrated by this workforce is unprecedented."
