The cybersecurity breach may not be fixed for a further week and possibly beyond that, the district health board's chief executive Kevin Snee said.
Some elective surgery and outpatient clinics have been cancelled as cyber experts work around the clock to get on top of the ransomware attack.
There were backups for all files and the system was slowly being rebuilt, but there was no definitive time-frame, Snee said.
''It becomes clearer as time goes on but I couldn't give you an end point to this and certainly even when we are back up and running fully there will still then be quite a recovery period afterwards because obviously you can imagine there are a lot of things to enter that are now in writing.''
It was too early to say what the cost of the cyber attack on its computer system would be, he said.
The system crashed on Tuesday after a ransomware attack on it from overseas.
''Obviously we do have insurance for this purpose. We are cataloguing it and it will only become clear in the aftermath of this how much it is all going to cost," Snee said.
It was difficult to be certain when the computer system would be back up and running.
''As everyday goes by we see improvements in the organisation because we are learning to live with it, we are learning to put in place work around, but it is less than ideal. The team are beavering away to get the IT system back up and running and I am confident we will get there at some point in the not too distance future, but when that will be I can not guarantee at this stage.''
While there was a risk to patient information there was no evidence to date to suggest medical files had been taken, he said.
The information systems team continued to work in shifts 24/7 and an incident control team was on hand to ensure operations could continue with minimal disruption.
Patient safety and service remained the number one priority of everyone working to resolve the issues and contingency plans were in place, Snee said.
Investigating the ransomware attack was challenging and complex and Waikato DHB continued to engage with experts across both the government and private sector, he said.
