Five years after Covid-19 reached New Zealand shores, we are bracing for the arrival of another deadly virus: a strain of bird flu called H5N1.
The current bird flu pandemic started in Asia in 2020, when alow pathogenic strain of H5N1 mutated into a high pathogenic strain.
Usually, high pathogenic strains causing illness and death are confined to domestic poultry like chickens and ducks. Outbreaks either peter out or are controlled – like the outbreak on two chicken farms in Otago in late 2024.
But this strain was different. It began to infect, kill and spread in wildlife – both birds and mammals.
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In October 2020 it began to spread rapidly across Africa and Europe, with devastating impact for some species. Numbers of great skuas in the United Kingdom, for instance, declined by 76%.
Just a year later, in late 2021, it reached Canada and the United States, having island-hopped via Iceland.
By October 2022, the virus was causing enormous numbers of deaths in seabirds and marine mammals across South America. Southern elephant seals were particularly hard hit, with more than 17,000 dead animals reported in a single breeding colony in Argentina.
In October 2023, it jumped from South America to South Georgia, South Sandwich and Falkland Islands, in the subantarctic. The Guardian reported at the time that “dead seals blocking the way” was preventing visitor access to explorer Ernest Shackleton’s grave on South Georgia Island.
In February 2024, two skuas became the first confirmed cases on the Antarctic Peninsula.
In October 2024, hundreds of king penguins and elephant seal pups were found dead from H5N1 in the subantarctic Crozet and Kerguelen islands. These very remote islands lie halfway between South Africa and Australia in the southern Indian Ocean, which means that the virus has already moved more than halfway around Antarctica.
Genetic testing showed that the virus on these islands originated in South Georgia, more than 6000km away. It is not known what species carried the virus to Crozet and Kerguelen islands.
New Zealand, Australia and Oceania are the last places in the world where H5N1 bird flu has not yet been detected.
The mammalian spread
To date, H5N1 bird flu has impacted at least 485 bird species and 48 mammal species worldwide. It is prevalent among marine mammals and seabirds that breed in large, tight-packed colonies, such as sea lions and gannets.
A breeding colony of tākapu Australasian gannets with the Farewell Spit lighthouse in the background. Photo / Alison Ballance
It also occurs in animals that scavenge the carcasses of infected animals, such as giant petrels and skuas. And it has infected dairy herds in the United States, leading to growing concerns about human cases – but as yet, there are no signs of person-to-person transmission.
As it edges closer, New Zealand officials have been on high alert. This includes testing any birds that look sick, and those that are in remote locations, such as New Zealand’s subantarctic islands.
They are also keeping an eye out for clues identified by their northern counterparts.
The largest gannet colony in the world is on Bass Rock in Scotland, home to more than 75,000 breeding pairs of gannets.
Bird flu struck in 2022, and at the height of that breeding season researchers counted just 21,000 occupied nest sites, a decline of more than 70%.
The normal light blue colouration of a gannet's eye (left) versus the black iris (right). Photo / Alison Ballance
At the time, researchers noticed some gannets with black eyes, rather than the usual pale blue. Nearly 80% of a small sample of these black-eyed birds had antigens against bird flu, showing they had been infected and recovered.
New Zealand ornithologists Rob Schuckard, David Melville and Steve Wood then heard of a sighting of a black-eyed tākapu Australasian gannet in Western Australia. Juvenile and subadult tākapu from New Zealand spend several years in Australian waters before they begin breeding, so birds from the two countries overlap and could potentially pass on infections.
As gannets are possible candidates for bringing bird flu to New Zealand, and as black irises might indicate a prior bird flu infection, the ornithologists set up a surveillance study of tākapu breeding at Farewell Spit.
Birds New Zealand study comprised monthly visits, starting in September 2024. On each visit, the team was alert for any signs of potential infection, such as sick birds in the colony, or dead gannets on the beach. No bird flu was detected.
One hundred and fifty gannets were caught, weighed and banded. Swabs from their mouth and cloaca were sent to professor Jemma Geoghegan at the University of Otago for a virome study, investigating background levels of viruses in various New Zealand bird species.
To their own surprise, the team caught and banded three tākapu with black irises and saw a further two or three. These are the first black-eyed gannets recorded in New Zealand.
Dr Megan Jolly, a wildlife vet from Massey University’s Wildbase hospital, was able to take a close look at one black-eyed gannet. Her initial assessment is that this bird had experienced some kind of infection, but not bird flu, that had caused inflammation in its eyes.
Preparing for H5N1
New Zealand has been preparing for the possible arrival of H5N1 bird flu, with the aim of minimising potential damage to wildlife, the agricultural sector and human health. A multi-agency working group has brought together staff from the Ministry for Primary Industries, Department of Conservation, Health NZ, and the poultry industry.
Early detection of the virus is a priority, and the public is asked to report signs of unusual illness in wildlife or sightings of three or more dead birds in one place to the exotic pest and disease hotline on 0800 80 99 66.
