The arrival of a highly pathogenic strain of avian flu could create a "permanent reservoir" of the virus within our bird population and present "persistent risk" of transmission to agricultural herds and humans working or interacting with them, according to a briefing to Health Minister Shane Reti early last month.
The briefing from the Ministry for Primary Industries, released to 1News under the Official Information Act, said the H5N1 strain was "highly likely" to arrive in New Zealand through migratory birds in the near future.
A global outbreak of H5N1, a type of high pathogenicity (HPAI) strain of avian influenza, has killed millions of wild birds and thousands of mammals on six continents.
It has spread to more than 40 species of mammal and has spread to dairy cattle in the United States. Australia reported its first ever human case in a child who became infected while travelling in India earlier this week. The H5N1 strain has not been detected in birds in Australia.
H5N1 was detected in mainland Antarctica in February.
ESR science leader genomics and bioinformatics David Winter told 1News that New Zealand is "quite unusual in the world" in that we have never seen a highly pathogenic avian influenza strain here.
"We just have been lucky up until now that they have never been present, they’ve never been part of our environment."
The current strain of concern has evolved and is different to previous variants.
He said it is "learning new tricks and being able to get into new hosts", increasing risk that a migratory bird could bring the virus into New Zealand.
Virologist Jemma Geoghegan told Breakfast the virus usually travels "by wildlife, usually wild birds". (Source: Breakfast)
"We just don’t really know precisely what will happen when it gets here because we don’t have a great deal of knowledge about what happens with avian flus in New Zealand."
Winter, who co-leads a Te Niwha research project improving surveillance and develop new tools for detection of avian influenza, said there was a risk that our wild birds could become a reservoir for the virus - a population chronically infected with a disease that act as a source of further infection.
"There is definitely the risk that once it is established, it will prove impossible to completely remove, and it may just circulate like it does in other parts of the world."
The risk when that happens is a "spillover" either from wildlife into farmed animals or wildlife into humans.
He said we do not have the full picture of what impact this might have on our native wildlife.
"From what we have seen from overseas, there is a risk for die offs in wild birds from this virus."
Ongoing work
The Ministry for Primary Industries (MPI), who is leading New Zealand's response, said it was undertaking "extensive work" alongside government agencies, primary sector organisations and other partners to prepare for the arrival of a HPAI.
Chief veterinary officer Mary van Andel said spread of avian diseases is being monitored, particularly towards the Ross Sea region in Antarctica where many birds migrate from.
"We know that early detection of HPAI in New Zealand is key to responding effectively and managing any impacts on biodiversity, agriculture, and trade."
Strong surveillance systems and some of the strongest import health standards in the world are in place to detect and manage a HPAI should it arrive here, she said.
"Biosecurity New Zealand is focused on response options that represent the best approach to mitigate the impact on primary sectors, especially poultry, protect our native species, monitor any possible spill-over events, protect human health, and help the sectors to report and contain spread while keeping themselves safe.
"It is also important to note that most of the world has been living with this for over five years, and this length of time has allowed Biosecurity New Zealand, in partnership with DOC, Health NZ and the Ministry of Health to take learnings and develop strategies around the management of this, should it arrive on our shores."
Veterinarians and the poultry industry have been alerted to the signs of infection, and van Andel said while we should be vigilant, the "isolated" spillover event involving dairy cattle in the United States was not cause for concern.
"HPAI has not been detected or reported in beef cattle to date, and information from the American Veterinary Medical Association is that most dairy cattle recover in two to three weeks. Given our huge dairy exports, it’s key to note that pasteurised milk remains safe and that no unpasteurised dairy products are imported from the US."
Van Andel said there was regular contact with international agencies regarding the behaviour of the disease and effective responses, including the US Department of Agriculture, the US Chief Veterinary Officer, and the Centre for Disease Control and Prevention.
'Management options in wild birds are limited'
DOC biosecurity manager Clare Stringer said if HPAI arrives in New Zealand it will remain in wild bird populations indefinitely.
"Management options in wild birds are limited and will be focused on population support for threatened species."
Work is underway to identify at risk species and high-risk sites to ensure support is provided if the disease arrives in the country.
Overseas evidence indicates the virus would be likely to affect colony nesting birds such as red and black-billed gulls, gannets, terns and other seabirds, she said.
"HPAI is transmitted between colony birds through secretions and faeces, and to predator/scavenger species such as raptors and marine mammals through exposure and consumption."
Stringer said vaccination could be effective for a few species to protect a core breeding population, with the Ministry for Primary Industries approving a controlled trial in five native species including the takahē and kākāpō.
"It is not possible to vaccinate all our endangered birds, but we can focus on those species in captivity where the full two doses of vaccine can be given."
A Ministry of Health spokesperson said public health agencies were "closely monitoring" the international situation around HPAI.
"While the virus can cause severe illness in humans, the World Health Organisation has assessed that currently the overall risk to humans is low. It is very rare for humans to be infected even if they are exposed, and HPAI is very unlikely to transmit from human to human at this stage."
The national pandemic plan is currently being updated and health guidance for people who could be at higher risk of exposure if the virus were to be found in New Zealand is being prepared.
The spokesperson added surveillance and testing infrastructure was being reviewed to ensure we are prepared to detect HPAI in humans.
"The previously reported overall low HPAI public health risk assessment for New Zealand is unlikely to substantively change based on the intelligence around this event to date. This does not preclude the ongoing and critical need to continue current preparedness activities."
Advice for those who could be exposed to wild birds or marine mammals include maintaining good hand hygiene, avoiding sick or dead wild birds and avoiding poultry and fur farms in countries outside of Australia and the Pacific Islands.
Impacts on humans
There have been nearly 900 human cases of the H5N1 virus globally since 2003, according to the World Health Organization.
So far, those cases have arisen through contact with infected animals rather than transmission between humans.
However, the mortality rate in those cases is of more concern. Just over half (52%) of the people known to have caught the virus have died.
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