The Ministry for Primary Industries is working to mitigate the impact of any avian influenza outbreak - since it cant control the movements of migrating birds that may bring it to Aotearoa.

New Zealand is one of the few places in the world to have no cases of the virus circulating among wild birds and poultry globally in recent years.

The highly pathogenic H5N1 strain has even spilled over into mammals, including humans, raising concerns too about its impact on human health.

MPI has teamed up with the Department of Conservation, the Ministry of Health and poultry and egg sectors to continue developing biosecurity and contingency plans in case highly pathogenic avian influenza (HPAI) arrives in New Zealand.

New genetic research confirmed that wild birds migrating from South America first brought the H5N1 strain to an island off mainland Antarctica - and to the Falkland Islands - which then rapidly spread among other wildlife on arrival.

Chief veterinary officer Mary van Andel said the study showed that given the unpredictable journey of wild birds that could travel with HPAI, it could still arrive here.

"It confirms what we already know about this wildlife-adapted strain of H5N1, and it really reminds us that the work we're doing to prepare is important."

"Up until now, New Zealand's geographic isolation has protected us from lots of pests and diseases, including highly pathogenic avian influenza, but this is a message to us that we can't rely on that isolation forever," she said.

MPI was particularly concerned about the evolved H5N1 strain, due to its rapid spread across the globe and how it had adapted to wildlife.

Van Andel said infected birds could die on their way here across the Ross Sea from Antarctica, but the risk was if they survived the journey.

"What's important about this particular wildlife-adapted strain, and what's different about it, is that we might not be able to prevent wild birds here in New Zealand from becoming infected because we can't stop wild birds that are infected with H5N1 highly pathogenic avian influenza from coming to New Zealand.

"But what we do have to do is work together amongst different sectors and different agencies here in New Zealand to mitigate the impact of the disease should it arrive here.

"If it does become established in wild birds, it doesn't seem likely that it would be able to be eradicated from those wild birds. And so our focus as New Zealand needs to be on reducing the impact."

Officials visited the UK and Australia in recent months to understand what risk mitigations worked at farm level, their complexities and costs, as well as wildlife surveillance, vaccinations and biosecurity measures.

Van Andel said laboratory testing facilities and meetings with Australia's epidemiology team gave valuable insights into the need to "balance disease control while maintaining business continuity" in affected regions as much as possible.

She said infected farms will likely have to control movement of stock, depopulate, decontaminate and dispose of equipment - measures which come at a cost.

But she said rigourous on-farm biosecurity now, before an incursion, could protect farms from infection and limit the impacts.

MPI was asking anyone who sees three or more sick or dead birds to report them to its 0800 80 99 66 hotline.

-RNZ