The head of the HSE says its IT system has been the subject of a major, sophisticated cyber attack.
The entire network has been shut down - but the Covid vaccination programme isn't affected. The Rotunda Hospital has already cancelled most appointments, except for women who are more than 36 weeks pregnant.
The National Ambulance Service is operating as normal, with emergency calls still being handled.
The HSE in the Shannonside region has confirmed that all testing appointments are going ahead as normal today, while walk-in facilities will also continue to remain open in the Shannonside region.