The number of confirmed swine flu cases has risen by nearly two dozen in the past 24 hours to reach 109 and is expected to rise further tonight, the Ministry of Health says.
Of the 23 new cases reported today, 13 were in Canterbury, seven in Auckland and three in Wellington.
A number of businesses and schools in Auckland and Canterbury closed after cases of swine flu amongst staff were confirmed.
Christchurch seafood processing plant Seafood Products Ltd sent all of its staff home after two workers contracted swine flu, while the Royal New Zealand Police College in Porirua postponed new courses.
Canterbury District Health Board communications advisor Michelle Hider said four cases of swine flu had been confirmed at Bromley School, which was now closed for seven days.
Two other Christchurch schools, Linwood College and Linwood Intermediate, each had a pupil with the virus.
In Auckland, St Patrick's School in Panmure was closed yesterday for seven days after one confirmed case of swine flu and 37 pupils reporting flu-like symptoms.
In Auckland, Westlake Girls High School, Kowhai Intermediate and Papatoetoe High each had one confirmed case, and Westlake's Year 12 level was closed for a week with 450 pupils and five teachers asked to go into home isolation.
At Wellington Zoo, 13 chimpanzees would receive flu vaccinations next week, and would be treated with Tamiflu if they showed any signs of illness, Radio New Zealand reported.
There was no evidence that swine flu could pass from humans to animals but chimpanzees could catch regular flu and suffered the same symptoms as humans.
At Hamilton Zoo there were no plans to vaccinate the eight resident chimpanzees but staff who worked with the animals had been vaccinated.
Meanwhile, health advice line Healthline answered about 1500 calls yesterday - double the usual amount of calls.
The call centre's capacity was being boosted to reduce caller delays.
The ministry had earlier warned against people deliberately contracting swine flu, as widespread absences from work and school would have a severe negative impact on the community.
Media reports in Australia and the United States said some parents have intentionally exposed their children to swine flu, believing that infecting them now will save them from a potentially more virulent strain in the future.
Deputy director of public health Fran McGrath said whether getting the virus to gain immunity to it was a good strategy would be known in the future, but at this stage New Zealand had a relatively small number of cases and the ministry wanted that to continue through the normal flu season.
"For individuals it tends to be a mild to moderate illness- it can be serious for some.
"But it's the impact of widespread absences, business continuity, schools and workplaces, that is like to be severe impact."
Health Minister Tony Ryall said the ministry was stepping up advertising mainly around the "helping not to spread the flu" message.
"Normally we would see about 31,000 medical admissions to hospitals a month during winter. Officials think we could end up with another 4000 or so if the swine flu peak matches the winter peak," he said.
"That is why we are working assiduously to try and prevent that from happening." Stocks of the anti-viral drug Tamiflu were beginning to run low in some pharmacies, although the Government held enough stock of the drug to treat 30 percent of the population.
Some pharmacies were down to their last few packets of Tamiflu while others had waiting lists ahead of new shipments arriving in the next few days, Radio NZ reported.
The ministry had refined its advice to arriving international travellers - only people with flu-like symptoms within four days of travel were now considered to be at risk of swine flu.
The Ministry on Health's national pandemic planning level was at 6.2 - the last level before code red, in which the virus is not contained and becomes widespread.
