Auckland City Hospital was yesterday on high alert after a nurse and her son tested positive for swine flu.
Access to a ward was restricted and operations were postponed.
The Ministry of Health said mother and son returned positive results for influenza A after returning on Saturday from a family holiday in Britain.
The nurse worked a 12-hour shift at Auckland City Hospital's Ward 71 - the renal care and transplant centre - on Monday while the boy attended daycare.
The ward has been closed to new admissions and is operating under strict infection-control procedures.
The restrictions are the first of this kind since swine flu reached New Zealand.
The ABC Childcare Centre on Kelvin Rd in Meadowbank , which the son attended, has also closed and is likely to stay shut until Wednesday.
Auckland City Hospital's chief medical officer, Dr David Sage, said the nurse did not have flu symptoms when she returned to work, but her child began showing them during the day.
The family went into voluntarily isolation at home while waiting for the child's test results.
It was then the nurse began showing flu symptoms. On Wednesday night, both swabs returned positive influenza A results.
The Ministry of Health is now tracing people who may have been in contact with the pair.
The positive results brought the total number of swine flu cases in New Zealand to 27 last night, up from 23 on Wednesday.
In Australia, the number of confirmed cases has topped 1000.
Dr Sage praised the actions of hospital staff who worked quickly to identify, isolate and treat those who were potentially affected.
"At this time, none of these people are showing flu-like symptoms," he said.
Auckland District Health Board spokeswoman Julia Lang said: "We've had to postpone our operations today while the situation is managed in the ward."
She said renal patients were being moved to other areas in the hospital.
Auckland Regional Public Health director Dr Julia Peters said her organisation was told of the cases Wednesday night, and contacted the childcare centre yesterday morning.
Nurses had been in touch with all "close-contact cases" and would remain in touch to deal with any of the families' concerns.
"If a child is obviously sick, parents should do everything they can not to send their child to daycare," she said.
The 29 children enrolled at the centre and seven staff are being offered Tamiflu and are in isolation at home.
The Ministry of Health's chief advisor on public health, Dr Ashley Bloomfield, said that as more people tested positive for influenza A, more workplaces, schools and childcare centres would be affected.
"People have been highly co-operative," she said.
"This has undoubtedly contributed to New Zealand's relatively low number of confirmed cases."
THE NUMBERS
* 27 Confirmed cases in New Zealand, up from 23 on Wednesday.
* 10 Suspected cases
* 74 Countries which have reported having swine flu
* 27,737 Total cases worldwide
* 141 Deaths worldwide
AUCKLAND CITY HOSPITAL
* Ward 71 closed to new admissions.
* Five patients in isolation.
* 19 staff in home quarantine.
ABC CHILDCARE CENTRE
* Seven staff and 29 children in isolation at home.
Swine flu strikes transplant centre
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