A dozen New Zealand Qualifications Authority (NZQA) staff have been quarantined after a colleague contracted swine flu.
The employee with swine flu worked on level 13 of a central Wellington office building, and was sent home on Friday.
When the diagnosis was confirmed yesterday afternoon NZQA quarantined a dozen people from level 13.
Other tenants were warned yesterday, and the building landlords were expected to co-ordinate a response tomorrow.
Public health officials yesterday warned that up to half the country could be affected if a pandemic took hold.
The number of confirmed New Zealand cases of swine flu rose to 19 yesterday, with two new confirmed cases being reported by Wellington's Regional Public Health overnight.
While numbers of those infected are relatively small, the flu strain is new and people have never been exposed to it, so it was expected to spread quickly.
In its present form, it was unlikely to result in a higher death toll than seasonal flu.
Both those today confirmed as having swine flu arrived in New Zealand on Air New Zealand flight NZ5 from Los Angeles on May 31 and became unwell after travelling together.
Swabs were taken from both on Sunday, and they and their close contacts were being treated with Tamiflu and had been asked to stay at home in isolation.
The confirmed cases have occurred in Auckland, Wellington, Christchurch and Hawke's Bay. Most have recovered.
The number of probable cases was 11, up from 10 on Monday, and there were 161 people in isolation or quarantine and being treated with Tamiflu, up from 92 on Monday.
There was no way of knowing with any certainty the exact number of people who could be infected if a pandemic established in New Zealand, director of public health Mark Jacobs said.
However, the more confirmed cases New Zealand has, the higher the chance that more serious illness and deaths would occur, he said.
While New Zealand appeared to have succeeded in keeping swine flu at bay, Dr Jacobs said, as time went on the virus would become harder and harder to manage.
Among the suspected swine flu cases are a group of 16 Gisborne Boys' High School students who recently returned from a trip to Brisbane.
They were isolated in a classroom today and were able to go home this evening, after five had exhibited flu-like symptoms.
Public Health staff have taken swabs and the ones who have viral symptoms were to be prescribed a course of Tamiflu.
In Wellington, staff have been attempting to track down close contacts of another person with a confirmed case of swine flu who was travelling on Air New Zealand flight NZ124 which arrived from Melbourne on June 5.
The two most recent cases in Wellington also involved workplace contacts and in both cases a number of staff had been sent home and had been offered Tamiflu.
The Engineering, Printing and Manufacturing Union (EPMU) said today employers should be prepared to take responsibility for the costs of workplace exposure to swine flu after a predicted increase in cases.
EPMU national secretary Andrew Little said quarantine came with significant costs to workers and that those costs should be met by their employers if the exposure was work-related.
"There can be a significant cost to a worker when they are quarantined, ranging from loss of allowances to not being able to work their second job and we believe that cost should be paid by the employer if the quarantine is the result of workplace exposure," Mr Little said.
"We are currently following up on four cases in which EPMU members have been quarantined following workplace exposure and are not being properly compensated for the losses they are incurring as a result."
