Christchurch Hospital's emergency department has been swamped with patients this week - driven by a spike in respiratory syncytial virus (RSV) cases amongst children - and Canterbury's urgent care facilities are also under significant pressure.
On Tuesday, 368 people turned up at the department; by 4pm Wednesday, 101 people were either being treated or waiting to be seen.
The high demand means some surgeries and appointments are being rescheduled, while some of Canterbury's clinics are closing their doors to walk-in patients.
On Wednesday night, Christchurch Hospital said it was over capacity and urged people to stay away from its emergency department unless they needed genuine emergency care.
The officer in charge of Canterbury's seasonal response, Becky Hickmott, told Morning Report the high demand had continued overnight, with occupancy still sitting at 100 percent.
"There's been a lot of viruses circulating around and what we have seen is a spike up in RSV for the children."
The number of sick children was "not unexpected" and it was important they were seen, she said, but people seeking hospital treatment for more "minor ailments" were presenting challenges for staff.
"We do want people to show up if they are very unwell, their children are very unwell, we do not want them to not show up."
However Hickmott said people suffering from minor injuries should do what they could at home to manage them and those with low-grade fevers could take over-the-counter medications and talk to their community pharmacists in the first instance.
The additional pressure on Canterbury's health system meant a total of 11 surgeries had to be cancelled yesterday, Hickmott said, all of which were being rescheduled.
"We absolutely hate taking that kind of action and we really apologise to everyone who's been impacted by these delays, but we sometimes have to take these measures to ensure we can continue to free up space and capacity for other people."
She said New Zealand's experience was closely mirroring what had been seen in the UK's National Health Service (NHS) where more people had been showing up for care "post-Covid".
"They had quite a tough spring and summer and I guess what we've been taking action in is preparing for this and realising we were going to have a bit of a hard time as well."
Hickmott said the high demand was "not unexpected".
"The border's been closed and now it's back open a lot of viruses are beginning to circulate again.
"It's been particularly hard on people this time round because they have been so unwell; but this was not unexpected, we did know and were worried this was going to happen."
Hickmott said healthforce staffing across the world was "really challenging" at present.
She said "alternative models of care" were being investigated to try and help support the existing workforce while the pressure on the health system remained.
This included looking at bringing in rehabilitation and other healthcare assistants to help "support and augment the workforce", she said, which would allow nurses and medical teams to keep working at the "top of the scope".
"We're acutely aware and just so grateful to not just our nurses within the whole system ... but all of our health staff who are really challenged in that space, as the whole world is."