Canterbury intensive care patients are being transferred to Dunedin as swine flu overwhelms Christchurch Hospital.
The Ministry of Health is closely monitoring pressure on intensive care units as swine flu rages on unabated.
Deputy director of public health Dr Fran McGrath said some ICUs were at capacity, but coping.
Among units hardest hit is at Christchurch Hospital, where 20 people were in intensive care yesterday, including 15 on ventilators.
Of those, 10 had or were suspected of having swine flu.
Intensive care specialist Geoff Shaw said the unit usually had a 12-patient capacity but extra staff had been brought in.
A cardiac ward had also been cleared to provide extra intensive care beds.
Elective cardiac surgery and other operations requiring a stay in ICU were being postponed to free up beds, he said.
"We are faced with a situation we've never had before. We've got more people requiring ventilators (because of the swine flu) and it's only expected to get worse," Dr Shaw told The Press.
However, the situation varied from region to region, with some hospitals reporting spare intensive care beds.
Some Christchurch patients had been transferred to Dunedin, which had free beds.
In Wellington, which was the first region to feel the pressure from swine flu admissions, there were three patients with flu complications on ventilators in intensive care.
They were in a serious but not critical situation, a spokesman said.
There were still some spare beds.
Wellington regional medical officer of health Stephen Palmer said there could be worse to come, with a spike in infections anticipated as schools returned this week from their mid-winter break.
The northern district health boards were coping, with Auckland last night reporting seven swine flu cases in ICU (22 percent of capacity); Northland two (50 percent); Counties-Manukau five (35 percent); and Waitemata three (43 percent).
Research showed the swine flu virus penetrated deeper into the lungs than seasonal flu, causing greater damage to the respiratory system.
This meant higher numbers of patients, including the young and people without underlying health conditions, were requiring ventilation.
"The extended length of ventilation time required by patients with pandemic influenza (H1N1) 09, which can be up to 14 days, along with the peak winter requirements, indicates that there will be continuing pressure on ICU capacity for the foreseeable future," Dr McGrath said.
The ministry was monitoring the situation and working with district health boards to manage hospital capacity, she said.
Meanwhile, the virus has been found to be more infectious than first thought.
Wellington-based researchers from the University of Otago today reported that in New Zealand a person ill with swine flu will on average infect almost two others.
This is the first published estimate for the "reproduction number" of the pandemic in the southern hemisphere.
To date researchers have used the lower estimate of 1.5 which was published early in the pandemic based on data from Mexico. NZPA WGT jaf kk kn
