University of Otago microbiology and immunology professor Jemma Geoghegan said it was highly likely the virus would come to New Zealand on migrating birds.
"Oceania is the last remaining continent that H5N1 hasn’t spread to yet, so I think it’s a matter of when, not if it comes here.
"I think that the virus will get to New Zealand and Australia and other geographically neighbouring countries, too."
Prof Geoghegan said scientists previously thought New Zealand was at low risk of having the virus come into the country because it was mainly carried by waterfowl.
But since then, the virus had started spreading to other migratory species and they now believed the risk of it coming here was "quite high".
"We have lots of migratory birds that travel all around the world and up to the northern hemisphere, and obviously down to Antarctica as well, where the virus is."
The H5N1 strain had been circulating around the world since about 2020.
"It’s been spreading mainly in wild birds and killing millions of them, and it’s now jumped over to cattle.
"It’s spreading to lots of other different mammals as well, including marine mammals.
"It’s spreading between cattle in the United States, causing quite a lot of havoc in their dairy industry.
"But human cases remain quite rare and low risk ... because the virus doesn’t appear to be spreading between humans yet.
"The humans are getting it from working with [infected] animals.
"The human case that died in Louisiana in the US recently was due to exposure to infected backyard chickens — it’s direct contact with those infected animals at the moment.
"However, we know that viruses can evolve and change, and so while public health risk is low currently to the general public, the risks for those people working with animals are not as low.
"Things might change in the future if the virus does acquire the ability to transmit between humans.
"The broad range of animals that it can now infect is quite stark and very worrying.
"That makes us on alert to really make sure that we know how the virus is evolving.
"Then if it does acquire the ability to spread between humans, then that’s something that we really need to be on top of and prepare for."
Prof Geoghegan believed New Zealanders needed be on alert and the country should invest in surveillance, so we know when it does arrive and we can take precautions for both animal and human health.
"We think that it’s got a very high mortality rate and kills around half of the people it infects, but we don’t know if more people have been infected that have had less severe symptoms and not been tested, so it’s hard to calculate.
"There’s some sort of margin of error around that, but we know that it can cause really high mortality rates in a lot of different animals, and so there is cause for concern for human health that it could also be hugely severe."
If it did arrive in New Zealand, even though it might not be a human virus yet, it would be "absolutely devastating" for our wildlife.
The present messaging to New Zealanders was that if you see three or more dead or sick birds, you should call the Ministry for Primary Industries hotline and they would do an investigation.
"The good news is that if it did start spreading among humans, we know we have flu vaccines and they can easily be adapted to current strains, and we know they’re safe and effective.
"So we’re not in the same position as we were at the start of Covid-19, for example."
Worldwide, more than 950 human cases of bird flu have been reported to the World Health Organisation, and about half have resulted in death.
The ongoing bird flu outbreak in the US, which began in poultry in 2022, has killed nearly 130 million wild and domestic poultry and has sickened 917 dairy herds.
Nearly 70 people in the US have contracted bird flu since April last year, most of them farm workers.
A patient with a combination of backyard chickens and wild birds in Louisiana was hospitalised on December 18 with H5N1 bird flu, and died recently, making them the country’s first reported human death from the virus.
The H5N1 virus was unrelated to the H7N6 outbreak that happened on an Otago egg farm late last year, Prof Geoghegan said.
