All 25 of the Rangitoto College students whose trip to Mexico sparked the first Influenza A/H1N1 tests in New Zealand are back at school on Monday, including the four confirmed with the virus.

They all passed any contagious stage, NewstalkZB radio reported.

While the number of potential cases of Influenza A/H1N1 appears to have peaked in New Zealand, health authorities are not yet prepared to let their guard down.

Health officials said there have been no signs of Influenza A/H1N1 spreading within New Zealand.

The Ministry of Health said there are four confirmed cases of Influenza A/H1N1 in New Zealand, 13 others probably have the virus and there are a further 89 suspected cases.

Deputy director of public health, Darren Hunt, said the confirmed and suspected cases have either contracted the flu overseas or been in close contact with those who have.

Hunt said a lot of effort is being put into ensuring there is no community transmission of Influenza A/H1N1, especially going into the winter flu season, and none has been seen yet, Radio New Zealand reported on Monday.

Hunt said he believed the swift reaction by health authorities here had kept the outbreak well contained, but that they were ready if the situation deteriorated.

The latest suspected case of the virus is that of an Auckland woman who traveled on flight NZ7 from San Francisco on last Tuesday. She was identified on Sunday as probably having Influenza A/H1N1 and health authorities are trying to trace passengers who sat near her.

A student from Hawke's Bay who returned from Los Angeles on Tuesday, earlier tested positive for Influenza A, which linked to the H1N1 strain.

The results of further tests to determine whether the student has Influenza A/H1N1 should arrive back from the World Health Organization laboratory in Melbourne on Monday.

On Sunday, the Ministry of Health said 360 people were isolated and being treated with Tamiflu, 91 more than the day before.

The head of the National Influenza Center, Sue Huang, said not much is known about the Influenza A/H1N1 virus and it is too soon to tell whether it has been contained.

Prime Minister John Key said on Monday the government did not over-react to the swine flu threat.

"We did everything we should be doing," he said on NewsTalkZB. "You can't sit back when there's a potential pandemic and do nothing."

(Xinhua News Agency May 4, 2009)