Sick patients are outnumbering hospital beds in parts of the country as staff struggle to keep up with a flood of winter-related illness.
Bitter winter weather has brought a spike in seasonal illness, bringing high, and in some regions, record numbers of patients affected by cardiac, respiratory and paediatric sickness.
Auckland's Middlemore Hospital was forced to open an area overnight usually used for day patients after it overflowed at 104 per cent capacity.
Patient numbers had reached 469 and with only 453 beds medical surgical beds available, a surplus of people were waiting, said Counties Manukau District Health Board communications manager Lauren Young.
Staff were also seeing record numbers of emergency patients, treating more than 300 people in each of past four days - surpassing the usual daily average of 270, she said.
"So many patients, so many days in a row is a problem for capacity. We are under control but asking people to see their GPs first unless it's an emergency," said Ms Young.
Patients at both ends of the age spectrum were particularly affected by winter ailments, said Auckland District Health Board emergency department clinical director Dr Tim Parke.
"Winter has certainly arrived and we are seeing the usual results of that. Our advice is for elderly people to ensure they see their GP for the influenza vaccine, and to seek medical assistance early if they are unwell. For young people, we advise them to look after themselves and rest."
Starship Hospital was at 99 per cent capacity, Auckland City Hospital 95 per cent, and Women's Health 86 per cent, which were all normal rates, said a spokeswoman.
North Shore and Waitakere hospitals were close to full in all departments except maternity, following a "typical" surge in patients with colds, chest infections and other winter illnesses in the past fortnight, said spokesman Paul Patton.
Bed were almost full at Waikato Hospital but the impact of winter illness was still considered minimal, said a spokeswoman.
Influenza-like illness was on the rise in Canterbury, with rates of the virus and hospital admissions increasing as winter progressed.
The predominant influenza strain was the severe A(H3N2), with some cases of A(H1N1) and influenza B viruses.
Fears over A(H3N2) have been growing in Auckland and South Canterbury, where last month the number of cases spiked in the two regions.
For the week ending June 10, those seeking consultations for influenza-like-illness consultations in Auckland reached 40.9 per 100,000 and in South Canterbury, 51.9 per 100,000, according to data from Environmental Science & Research.
Like other strains, symptoms can include fever, headache and a dry cough, but the A virus was associated with "more severe outcomes", said National Influenza Specialist Group spokesman Lance Jennings.
A major outbreak of A(H3N2) could cause a surge in hospital admissions and deaths, he said.
Influenza is estimated to kill 400 people in New Zealand each year.