Over the past few years, more and more birds have come to harbour new strains of this deadly virus as it continues to evolve to infect new species. It is now causing a panzootic (a pandemic of animals) among wild aquatic birds.
The virus, known as highly pathogenic avian influenza virus, has likely already killed thousands of birds worldwide. What’s more, spillovers to non-avian hosts such as mammals are becoming increasingly common. While only a few human cases have been reported, cats, foxes and sea lions are being infected at an alarming rate.
Despite intercontinental transmission of highly pathogenic bird flu variants during the past 20 years, no cases have been reported in New Zealand — yet. Australia is also considered free of the virus, although a few years ago a strain in chickens was thought to have evolved locally.
One reason we emphasise "yet" is because each spring, thousands of migratory birds arrive in New Zealand. Will they bring these deadly strains of avian influenza with them? An unwanted viral hitchhiker could have devastating consequences for our biota and industries.
New Zealand is assumed to be at low risk from highly pathogenic avian influenza. We are thought to be too far away from other landmasses and not on routes that migratory waterfowl usually take.
Any migratory birds that do make landfall in New Zealand are thought likely to die of the disease before reaching our shores, but some wild birds might experience asymptomatic infections, even of typically highly pathogenic strains. Also, the recent expansion of susceptible host species, including to marine mammals, increases the risk that some species might carry the virus.
As for geography, research suggests wild bird migrations are responsible for transmitting the virus from Europe to the Americas across the Atlantic, as well as throughout Eurasia. So why not to New Zealand? Are we really just too far away?
If this highly pathogenic avian influenza virus was to arrive, New Zealand is not as prepared as it could be. The major reason is that we have very little active virus surveillance of wildlife.
New Zealand monitors livestock, including cows, sheep and poultry, for a range of diseases. But the impact of this virus on people and non-poultry livestock is likely to be minimal.
The first signs might be the death of seabirds or marine mammals. While perhaps not as iconic as a kiwi or kākāpō, New Zealand is home to a great many seabirds found nowhere else on the planet.
Some species, such as tara iti (or fairy tern) are critically endangered — there are only about 50 individuals left. A virus such as this could directly drive the extinction of species with such low numbers.
Given this risk, the United States took action to vaccinate the Californian condor against avian influenza — but only after finding 21 dead condors (4% of the remaining population) which had tested positive for the H5N1 strain.
It is clear that to first spot and then stop a virus such as this, we need to look at the entire ecosystem — where humans, animals and the environment are interconnected. This is known as the "one health" approach.
While this makes intuitive sense, the reality is that disease surveillance affecting humans, domestic animals and wildlife is largely siloed and under-resourced.
There is limited integration of activities across these domains. The result is that we are ill-equipped to track and respond rapidly to this deadly virus if it arrived in New Zealand.
It is time to provide a more enhanced and integrated one health surveillance system, involving expertise across universities, research institutes and government departments to re-evaluate our pandemic (and panzootic) preparedness.
— Prof Jemma Geoghegan holds the Webster Family Chair in Viral Pathogenesis at the University of Otago; Nigel French is the distinguished professor of infectious disease epidemiology and public health at Massey University.
