The Emergency Department at Letterkenny University Hospital has been extremely busy this week with high numbers of people attending.
The impact of the ransomware attack on the HSE IT systems means that patients attending the Emergency Department are facing extremely long delays as essential services like blood tests and diagnostic services are taking much longer than usual.
The hospital says patients needing urgent care will be prioritised.
They're asking people to contact their GP or GP Out Of Hours Service in the first instance if their health problem is not urgent.
Saolta Hospital Group have apologised for the long waiting times that patients are currently facing.