The centre specialises in research on zoonotic diseases -- ones which animals can transmit to humans -- and Dr Kousoulas said his researchers had been focussing on the H1N1 virus.

"If the avian flu and human flu infect a pig, the pig becomes a mixing vessel. The viruses mix in the pig, and a new virus comes out," he said. "Because it changes so fast, it is highly possible that a new virus evolves that is highly virulent in humans."

Companies that produce vaccines were now faced with a dilemma over whether they should produce vaccines for seasonal flu, swine flu or both, Dr Kousoulas said.

"If we produce both vaccines, then we will have to produce much less of each, which means not everybody could be immunized," he said.

Another fear was that swine flu would mutate so much that the new vaccine would be useless by the time seasonal flu returned to North America in the New Zealand spring, he said.

"Now we're all holding our breath to see what happens in the Southern Hemisphere with the swine flu and what happens in the (American autumn)," Dr Kousoulas said.

He said that BIOMMED was looking into where the swine flue actually originated, and that appeared to be in either New Zealand or China.

The research centre had $US10 million in funding from the US National Institutes of Health to create a centre for experimental infectious disease research.

"We're interested in every virus or bacterium that could infect animals or a human," he said.

A New Zealand virologist, Dr Richard Webby, of St. Jude Children's Research Hospital in Memphis, director of the World Health Organisation's collaborating centre for studies on the ecology of influenza viruses in animals and birds, has previously confirmed the A(H1N1) pandemic virus was specifically a swine virus.

Other researchers have shown that some of the eight segments that make up the swine flu virus were related to influenza viruses found in swine, both in North America and Eurasia, and that segments from the North American lineage, were related to a swine virus isolated in 1998 that was a triple reassortment of avian, swine and human viruses.

Dr Kousoulas' team has separately been studying effectiveness of novel drugs against swine flu, using a virulent H1N1 strain which caused a severe outbreak in 1930 as a surrogate for the current influenza.