It says the lack of access to patient information in hospitals is creating an "extremely high risk" environment.
Some cancer services like chemotherapy are operating at close to full capacity - but there's huge disruption in areas such as mental health.
HSE chief executive Paul Reid says it's going to cost a lot of money to recover from the cyber attack.
Over €1 Million Secured For Outdoor Recreation Projects In Wicklow
Average Rent Of A Three-Bed In County Wicklow Is Up 6.1% Year-On-Year
Wicklow TD Slams Government Over “Shameful” Refusal to Fund Rehills Development In Bray
Young Voices of Wicklow Unite at Comhairle na nÓg Youth Summit