Scientists fear swine flu could mutate into a strain resistant to Tamiflu at present the only defence against the deadly virus with a vaccine still several months away.
As the Mexican death toll rose above 150 last night, New Zealand health authorities confirmed 14 definite or probable cases.
Eleven international travellers arriving here from the Americas with suspected swine flu symptoms were picked up at border screening yesterday and put into isolation.
Authorities are still trying to contact 15 passengers from flight NZ1, which carried the infected Rangitoto College pupils from Mexico via Los Angeles on Saturday.
The Government has ramped up its powers to deal with a potential epidemic by making swine flu a "notifiable disease" through a special order-in-council giving it the ability to forcibly quarantine suspected carriers if necessary.
Environmental Science and Research virologist Sue Huang, head of the WHO national influenza centre in Upper Hutt, said swine flu strains were changing so rapidly that there was a threat one could combine with a Tamiflu-resistant virus already in circulation.
"This virus really caught us by surprise," Dr Huang said.
It was vital health authorities took advantage of the fact swine flu had not yet become resistant to the retro-viral drug, she said.
Five cases of Tamiflu-resistant seasonal influenza have been diagnosed in New Zealand in the past nine months. Tamiflu-resistant H1N1 flu strains were becoming more prolific in Hong Kong and the US.
Test swabs for the killer virus are now being analysed at the ESR's Upper Hutt laboratory.
Dr Huang said it usually took about six months to develop a vaccine for a particular strain and "get it on to the shelves".
Health Minister Tony Ryall said the move to make swine flu a notifiable disease was "a precautionary measure".
"It is now on the schedule for the Epidemic Preparedness Act, so if there's any need to bring in that act it's much more straightforward."
Under the 2006 act passed when fears of a bird flu pandemic were at their height the prime minister can grant "special powers" to government ministers, the chief of police and judges.
The Health Ministry is enforcing strict border controls, screening every international flight from affected areas.
The quarantined travellers identified yesterday were initially treated in Middlemore Hospital but were last night in isolation at a hotel.
About 200 people were still in voluntary isolation last night. Those who had no symptoms and had had three days of Tamiflu treatment were expected to leave isolation today.
- The Dominion Post