Two North Shore schools are at the centre of a swine flu scare after tests showed the disease believed to have killed scores of Mexicans may have infected a group of Auckland students.

Initial tests have shown around 10 of 22 students from Rangitoto College in Mairangi Bay who arrived home on Saturday from a trip to Mexico are "highly likely" to be infected with some form of influenza A strain.

Fourteen students and two parents from Northcote College also arrived home from Mexico that day and are being followed up by health officials.

Principal Vicki Barrie said none had shown flu-like symptoms.

The World Health Organisation fears the new influenza A virus, a mix of human, pig and bird flu strains, has the potential to become a global pandemic. It jumped species, infecting more than 1000 people across Mexico and killing as many as 81; 20 deaths have been confirmed.

Cases have been reported in California, Texas, Kansas and New York. A British Airways crew member was taken to hospital in London with symptoms after returning from Mexico.

Health Minister Tony Ryall said last night 13 Rangitoto students had been tested and 10 had returned positive results for influenza A. There was no guarantee they had swine flu, but his officials considered it highly likely.

"All precautions are being taken to allow for this. However, I am also informed none of the affected patients are considered seriously ill."

Some of the other students who had not been sick were now showing symptoms, however.

Samples from the 10 students who had tested positive for influenza A would now be sent to the World Health Organisation laboratory in Melbourne to ascertain whether it is the H1N1 swine influenza." H1N1 influenza is a subset of influenza A.

The 364 passengers on Air NZ flight NZ1, on which the Rangitoto students returned, are being urged to see their GP or a health professional if they develop flu-like symptoms.

But the airline said filters on its airconditioning killed 99.9 per cent of airborne viruses including influenza.

The anti-influenza drug Tamiflu has been released from Middlemore Hospital to the Auckland Regional Public Health Service to treat patients and those who have had contact with them.

The Ministry of Health said it was working closely with the service, district health boards and Government agencies including Agriculture, Customs and Education.

The 22 Rangitoto Spanish language students and their three teachers were in Mexico for three weeks. Some were sick with flu-like symptoms, and the public health service was notified on Saturday by a GP and a North Shore Hospital physician.

David Boyens, of Mairangi Bay, told the Herald last night he was relieved that tests on his 16-year-old twins Thomas and Anja, who went on the trip, had put them in the clear.

But because swine flu could not yet be ruled out for the whole group, health officials had told them to act as if they had been exposed. They would be given Tamiflu and were in home isolation.

"I was down to go to Australia [today] but I was told I can't - just cancel that and stay at home."

The public health service's clinical director, Julia Peters, said the sick had respiratory illness symptoms including blocked nose, cough, fever, aching muscles, headache, loss of appetite, sneezing and watery eyes.

"One student was hospitalised, probably more as a precaution [on Saturday night]. The physicians do not think he has influenza. He's just being kept there as a precaution."

The sick and the well had agreed to stay in "home isolation" until the preliminary test results were known.

"Where there are non-symptomatic people, we have said other household members can go about their normal business," Dr Peters said. "If the preliminary results are all clear it is likely we would be allowing people who are well to go to school and work [today]."

On Saturday, the World Health Organisation activated stage three of its six-stage global influenza plan. Stage three puts nations on "pandemic alert", urging them to intensify surveillance for unusual outbreaks of influenza-like illness and severe pneumonia, but is less serious than the declaration a pandemic is under way.

Stage 3 is activated when there is "no or very limited human-to-human transmission".

The WHO declared the outbreak a public health emergency of international concern, but said there were gaps in knowledge on the virus.

Director-general Margaret Chan said symptoms of swine flu were similar to seasonal flu, but could include severe pneumonia causing death. Sometimes there were no symptoms.

The WHO said the current seasonal flu vaccine did not contain swine flu virus and it was not known whether the vaccine would protect against it.

The US Centres for Disease Control and Prevention said Tamiflu and Relenza seemed to work against the new virus.


Travellers returning from areas of north and central America affected by the Mexican swine flu are being advised to seek medical attention if they are displaying flu-like symptoms.

And all passengers flying from North America to Auckland will be stopped from today, read a statement about the flu and asked to visit a doctor if feeling unwell.

Health Minister Tony Ryall said last night anyone on Flight NZ1 who came in from Los Angeles and anyone who came from Mexico should have those symptoms checked.

He upgraded the alert level to code yellow - one below the highest code red. "[That means] increased surveillance and people arriving on North American flights will be told that if they have flu-like symptoms they should be in touch with their doctor or other health authorities."

Warning signs of severe flu are rapid breathing or difficulty breathing, chest pain, severe vomiting or if a child is difficult to wake up.

Sick people should use tissues to cover sneezes and coughs; avoid contact with others and stay at home; wash and dry hands often; and avoid touching their eyes, nose and mouth.