The H5N1 strain has been spreading rapidly around the world since late 2021.
Recent confirmed cases in birds and seals show it has spread to sub-Antarctic islands on the other side of the world, still far away but approaching New Zealand's neighbourhood in wildlife terms.
It is a strain that has decimated bird species as it travels around the globe, killing 81 million poultry and aquatic birds in the United States alone since the start of 2022.
Late last month the virus was found in the Atlantic subantarctic, Falkland and South Georgia islands.
University of Otago virologist Professor Jemma Geoghegan said an outbreak in New Zealand could be truly terrible.
"It's killing birds and other marine wildlife in unprecedented scales around the world and so the potential threat to New Zealand, it could be catastrophic for many of the species that are sort of already tinkering on the brink of extinction," Geoghegan said.
She said it was just a matter of time before the virus breached New Zealand's borders.
It could be next year or in five years - and could be kept out for longer, with luck and good management.
Massey University infectious disease professor Nigel French said the biggest risk for transfer of infection from different countries was through migratory wild fowl.
"We have around 200,000 or so bar tailed godwits and red knot, mainly those species that come down from the East Asian Australian Flyway from Arctic downwards. They're a relatively low risk compared to the waterfowl. And we don't have any migratory waterfowl," French said.
But French said an outbreak could prompt mass culls on poultry farms.
"It's a big concern for any poultry industry and any country. Some countries have had really big culls of poultry as a result of infection in flocks and obviously we have a poultry industry here in New Zealand, so there would be discussions around how we manage that from a biosecurity point of view," French said.
French said the official risk level was low and the focus had to be on early detection.
"We can't wait till it's in multiple birds and multiple flocks before we decide to do anything about it. It's got to be really, really good surveillance and that involves the whole public as well as MPI and the Department of Conservation.
"And then making sure you have mitigation measures in place to make sure you can stamp it out and deal with it as soon as it does arrive," French said.
The virus can infect and kill other animals, but there is currently no evidence of mammal-to-mammal or human-to-human transmission.
In a statement, the Ministry of Health said it was monitoring the international situation around the HPAI and H5N1 strains and a working on a response plan if the virus reaches Aotearoa.
"While the virus can cause severe illness in humans, the World Health Organization has assessed that the overall risk to humans is low. It is very rare for humans to be infected even if they are exposed."
Professor Geoghegan fears the virus could mutate if multiple mammals such as sea lions or seals have been in contact with the same infected bird.
"If the virus does adapt to spread between marine mammals, there's nothing to say that then it can spread between humans as we are mammals as well," Geoghegan said.
French described the virus as very low risk, but high consequence.
From January 2022 through to the end of December in 2023, nine people caught the virus resulting in five deaths, according to the Centres for Disease Control and Prevention.
The United States government is working on a vaccine and is about 18 months away from finding a jab.
Department of Conservation technical ecology adviser Bruce McKinlay said it was trailing its own vaccine on a small number of endangered birds.
"We've got a kakī or black stilt, takahē, kākāpō, tūturuatu or shore plover and red crowned kākāriki and there's currently no commercially available vaccines in New Zealand, so it's all released by MPI that require two injections to be effective," McKinlay said.
Ministry for Primary Industries chief veterinary officer Mary van Andel wanted people to look out for possible infections.
"Anybody who sees a significant number of birds who are sick or dying, they can report it immediately to our pest and disease hotline so that's 0800 80 99 66 and we're really asking them not to touch these animals. Once they get through to the hotline our investigators will provide some information about what the next steps are," van Andel said.
She said people should take photos and videos if they suspected birds were unwell.
