Waikato DHB is sending some patients to the private sector to catch up on a backlog of non-urgent operations.

It has been five weeks since a ransomware attack crippled its systems and forced a massive overhaul of its operations.

Waikato DHB chief executive Kevin Snee tells Morning Report private clinics will help with a backlog of about 200 elective surgeries.

The backlog also included thousands of outpatient appointments.

"We're in the winter months and most DHBs are running at full capacity, so we'll try to use the private sector or bring in physical capacity into the hospital where we can," he says.

Radiation and cancer services were now operational.

While services have gradually resumed, some IT systems are still to be restored and manual workarounds remain a daily reality for some staff.

Snee says the DHB was back at 90-to-95 per cent operating capacity overall.

"All of the services have a level of disruption but we have our core systems back up and running ... but obviously these core services have a range of interconnecting services to support them and some of those aren't yet functioning.

"It's going to take a number of weeks before we've got everything back up and running and then of course beyond that there is continued data input from all the data we've been collecting manually over the last five weeks. Of course then there's the patient who had non-urgent treatment that didn't take place, but will have to take place over the next few months."

There has been no contact with the cyber criminals by the DHB and Snee says the lessons learned from the incident should be applied across the wider DHB system.

"The DHB systems are pretty complex and the interconnectedness, both within the DHB and the wider health system, is complex... All DHBs will find that to rebuild the system takes time."

One IT system for the whole country could make it easier, with a consolidation of expertise within the new Health New Zealand system, for example, making the system more secure, he says.

• RNZ