New research details the rapid spread of the H5N1 strain into wildlife on an island off the coast of mainland Antarctica, and in Falkland Islands.
The report, published in the journal Nature Communications, said the fragile ecosystem of South Georgia had been free of the virus until it was first detected during the 2022-23 summer season.
Genetic assessment found the virus had spread from South America, probably through migratory birds.
It infected a range of birds such as black-browed albatross, skuas, kelp gulls, as well as marine mammals such as southern elephant seals.
"Much like New Zealand, Antarctica has never had the really pathogenic strains of this form of virus before," Massey University veterinary professor Brett Gartrell told RNZ's Morning Report programme today.
"The really scary thing for us about this latest report is the range of species that has been affected."
Birds like skua, giant petrels and kelp gulls can move right around the sub-Antarctic so there was a risk the virus would get to New Zealand's sub-Antarctic Islands and from there to the mainland.
"In the worst case scenario, if it gets into some of the albatross species which do make landfall in New Zealand, that could come in that way as well."
The good news was at this stage Antarctic penguins did not seem to be affected, he said. If they had been, the spread would have been much more rapid.
The research would give an idea of how the strain will behave if it makes it to New Zealand.
Will the H5N1 strain get to NZ?
At this point the virus was on the other side of Antarctica, so it would be a while longer before it got to the New Zealand side, Gartrell said.
There was still a degree of uncertainty on whether it would reach the New Zealand mainland.
However, five years ago the virus was thought unlikely to reach Antarctica, and it had since changed behaviour, being able to infect a greater range of bird species than ever before.
"That's why its been able to spread so far."
A Department of Conservation avian flu vaccine trial on New Zealand birds indicated immunity would kick in after two vaccinations and about six to eight weeks, he said.
It would be helpful in protecting some of the most vulnerable species which are managed intensively. "But there's going to be a lot of species that are going to be put under the hammer by this virus should it get to New Zealand."
Doc has vaccinated 50 native birds, including takahē, kākāpō, tūturuatu, kakī and kākāriki, as part of a trial to see if it is an effective line of defence, The Guardian has reported.
