Norovirus, surgery for burns and trauma and the onset of "asthma weather" have combined to push one of Auckland's major hospitals beyond capacity.
Middlemore Hospital has been running at up to 8 per cent above capacity this week because of the influx of patients with serious and life-threatening afflictions.
Norovirus has closed one ward and left eight beds unusable in the quarantine zone, while serious cases - including a 2-year-old boy burned in a Mt Wellington house fire and a man who needed two fingers reattached after a workplace accident - have consumed theatre hours at the South Auckland hospital.
Middlemore central manager Dot McKeen said a combination of factors since the weekend had led to the high patient numbers.
"There's no real reason, sometimes this just happens," she said. "We've had a lot more surgeries that took longer and with a longer time of stay.
"It is more common in winter when we get a big increase in respiratory illness and chest infections - this has been more surgery-based."
A cool and windy start to spring was spurring "asthma weather" and there was also an outbreak of highly contagious norovirus, she said.
"Currently we have one ward that is closed to new admissions as several patients are very infectious. This also restricts our capacity."
Middlemore Hospital has 14 operating theatres and about 800 beds, plus an extra 200 beds across facilities operated by the Counties Manukau District Health Board.
"So that's a lot of surgeries," Mrs McKeen said. "We have had a couple of big cases like the child that was in the house fire. That takes up a lot of theatre time because you have got to have grafting and then recovery."
There were nine other patients in the burns unit, she said.
The hospital managed the demand by using its "pod" system that allows wards to be extended in times of high demand, a spokeswoman said.
While Middlemore was overflowing, Auckland's other hospitals remained in check. Waitakere Hospital was at 92 per cent and North Shore at 94 per cent. Auckland and Starship hospitals were running at a combined 95 per cent occupancy.
In Northland, Whangarei Hospital was operating at full capacity yesterday and Bay of Islands and Dargaville hospitals' daily bed numbers had also been tracking quite high, a Northland District Health Board spokeswoman said.
"We are experiencing a late winter surge, especially children with bronchial illnesses," she said.
The Waikato District Health Board was not experiencing high occupancy, a spokeswoman said.
Mrs McKeen said a number of discharges yesterday had begun to bring numbers down, but advised patients to see their GP as soon as they felt sick, be vigilant with hygiene and around potentially dangerous activities - especially barbecues and swimming - as summer approached.
Patient gives staff top marks
Diagnosed with a brain tumour in 2012, Geraldine Devoy has spent a lot of time in hospitals.
Most recently, she was admitted to Middlemore Hospital on Sunday for tests.
Mrs Devoy, 54, has spent time in hospitals in Auckland, Hamilton and Tauranga as she seeks treatment for her craniopharyngioma.
The mother of three said hospitals always seemed busy to her - and the past three nights were no different.
"It has not been as busy as it has been at other times. Hospitals are always busy, in my opinion. Sometimes when it is really busy it just depends how much staff you have to keep the momentum.
"The staff here are wonderful, they are lovely."
Mrs Devoy was discharged yesterday afternoon, and said the three-night stay was a standard length of time for her.
Tight squeeze at Middlemore
• Has been running at 8 per cent above capacity this week.
• Norovirus has closed one ward, meaning eight empty beds cannot be used.
• Time-consuming surgery - including for burns and a finger reattachment - has lengthened patient stays.
• On Tuesday, 34 people needed beds before the day's admissions had arrived.
• Whangarei Hospital was also at capacity, but others around the upper North Island are tracking normally.