The Situation

Influenza viruses have been a part of life for as long as history can trace, changing and adapting with their environments.¹ So called “bird flu” are type A influenza viruses, causing natural infections in birds. Most of the possible combinations of membrane protein subtypes (H1 to H15) and membrane enzyme subtypes (N1 to N9) have been found in birds.² Influenza A viruses have caused several pandemics in the past—such as the Spanish flu, which was the H1N1 subtype³—making it plausible to happen again.

The natural reservoirs for avian influenza subtypes are wild water birds, where infections usually cause no or mild symptoms. Problems arise when the infection jumps to terrestrial birds like chickens and turkeys. Here, the virus can evolve to become much more infectious and deadly, spreading to other species, including mammals. The viruses may find different pathways of infection and cause different symptoms.⁴

The currently most common, highly infectious subtype is H5N1,⁵ which itself developed several subtypes (called Clades).⁶

H5N1 is not new; and scientists have long known it can infect mammals.⁷ However, this subtype is spreading widely at the moment. Globally, news reports detail the culling of flocks of chickens, ducks and turkeys. Recently, 959 dairy cow herds in 16 U.S. states have tested positive,⁸ and domestic pets, such as cats,^9,10 are found positive worldwide.

Species with confirmed infections of H5N1:¹¹

• many kinds of wild and domestic birds, including poultry
• (wild and domestic) cats, dogs and pigs
• sheep, goats, alpacas and cattle
• small mammals, like mice and rats, squirrels, voles and hamsters, rabbits and pika
• otters, ferrets, minks, raccoons, skunks and opossums
• marine mammals, like seals, walrus, dolphins and porpoise
• polar bears and black rhino

...and humans. Almost one thousand human cases have been confirmed, resulting in 466 deaths.¹² Of those, 261 cases of human infection with H5N1 have been reported from the Western Pacific Region (142 deaths), namely from Australia, Cambodia, China, Lao PDR and Viet Nam.¹³

Infected wild mammals often show symptoms of nervous system damage, including seizures, ataxia (trouble walking), trembling, and abnormal behaviours like circling or vocalisations.¹⁴

Problems beyond the virus itself

The implications of bird flu extend far beyond the virus's direct impact on infected animals and humans.

Mass Culling:

Commercial and backyard bird flocks are culled as a precaution, even when only a few birds actually test positive. For example, since February 2022, over 156 million birds have been "affected" in the U.S. alone.¹⁵ Culling and cleanup costs are immense, with taxpayers often footing the bill. During a 1983 outbreak in Pennsylvania with (“just”) over 17 million birds affected, the total losses came to 63 million USD (~ 110.6 million NZD), while poultry meat and eggs prices sky-rocketed. The U.S. already face rising egg prices in the current outbreak.¹⁶

Infectious disease outbreaks in humans can also cost billions and billions of dollars, should the spread continue.¹⁷

Animal use in Diagnostics:

Entirely unrelated animals suffer because of the outbreaks, too. Several of the laboratory methods used to detect and study the viruses rely on animals or animal products (like blood or embryonated eggs).¹⁸

The WHO lists in their Influenza diagnosis and surveillance manual:¹⁹

• Virus Isolation in cell culture: several animal-derived lab ingredients, including
  • specific proteins (isolated from animal blood)
  • gelatin (isolated from meat and leather)
  • Foetal Bovine Serum (which is harvested from the calves inside slaughtered pregnant cows)
  • trypsin (which can be acquired from animal-free sources, but most times is not).
• Virus Isolation in eggs:
  • three embryonated chicken eggs per sample (fertilised nine to 11 days prior)
  • they are infected, incubated for up to three days and then chilled.
• Virus type identification: additionally to the reagents required for isolation, specific antibodies and antisera are needed;
  • these are traditionally harvested from animals (cattle, horses or rabbits) who were repeatedly injected with antigens to then harvest their immune response with the blood.

Animal Research

Research on bird flu involved countless animal experiments, even before this became a pandemic concern. There have been “established models” to study infections and transmission for a long time.²⁰ Over decades, ferrets,^21,22 minks,²³ foxes,²⁴ skunks,²⁵ raccoons,²⁶ pika,^27,28 guinea pigs,²⁹ mice,³⁰ rats,³¹ voles,³² rabbits,³³ pigs,^34,35 chickens and other birds³⁶ were purposely infected all over the world with many different strains, studied and probed and most often killed for dissection.

As is to be expected, the number of studies has surged worldwide with the recent outbreaks, including many chickens,^37,38 ducks,³⁹ mice,^40-42 guinea pigs,⁴³ ferrets,^44,45 and monkeys,⁴⁶ with many being killed (the remainder of papers did not state the animals’ fate). In addition, the outbreaks cause countless sampling of animals found dead or dying, using the laboratory methods mentioned earlier.

We found no experimental studies from within New Zealand, only sampling of populations for risk assessment.^47,48

New Zealand specific

An outbreak on an egg farm in Otago (H7N6 strain) led to all “affected” birds being killed. Ministry for Primary Industries (MPI) had decided to “depopulate” the approximately 200,000 chickens on the premises.⁴⁹

Depopulation means to cull a whole population of a shed or property. The methods can involve freezing, gassing, suffocating or turning off shed ventilation and letting them die of heatstroke. According to Animals Aotearoa, none of these are ruled out by the government.⁵⁰

We at NZAVS deem none of the methods “humane”, yet gassing is an accepted slaughterhouse practice for poultry.⁵¹

According to the MPI, the latest round of testing, involving 36 flocks across five farms linked to Mainland’s Hillgrove property, found no sign of the virus. Which, again, was a different strain to the one rampaging through the U.S. and Europe right now, and is also not related to the strain identified in Australia earlier in 2024.⁵²

So far, the virus strain jumping species gaps over to mammals has not been detected in New Zealand. The biggest risk, other than migrating birds carrying it, comes from overseas travellers returning while being infected. Even the H5N1 strain has not been transmitted from human to human yet.⁵³

A situation called spill-back can become a concern for our precious native birds, where an initial infection spills over and causes outbreaks in farmed birds and then from there “spills back”, infecting wild animals.⁵⁴

How scary is it for humanity?

For the H5N1 influenza virus to spark a human pandemic, it must undergo several specific mutations. The viruses in birds, cattle, and people so far show no signs of the mutations that would allow H5N1 to better latch onto human receptors. Additionally, receptor affinity might not be the only barrier the virus needs to overcome. And while theoretically, the virus only needs enough time to do that, it is uncertain that it can, considering how long it has been around.⁵⁵

A serious aid to the viruses becoming human transmittable, however, is the disease-prone way we humans keep animals for food. Industrial farming practices provide ample opportunities for viruses to adapt and spread fast.

In birds, the viruses are shed in faeces and respiratory secretions. They can be spread by direct contact, through feed and water, and also be carried on farm equipment from farm to farm.⁵⁶

Small mammals like mice and rabbits are drawn to farms by easy access to food and maybe even carcasses of dead birds, and dry spaces to hide. Their presence invites other predators in. Both can potentially bring viruses in from the wild or readily spread them between barns or farms.

Anyone who ever worked on or has visited a farm knows that faeces is omnipresent, run-off is almost as inevitable as “pests”, and the animals are kept in much higher densities than they would prefer in the wild. Daily close contact of farm workers with the animals and their products creates opportunities for diseases to jump over.

With currently over 41.5 billion animals farmed for food worldwide (yes, billion with a B),⁵⁷ there is plenty of scientific research to verify the connection between animal agriculture and the spread and spill-over of zoonotic diseases to humans and wildlife.^58-68

Zoonotic diseases are already causing over two million human deaths every single year.⁶⁹ So, let’s not pretend like the bird flu viruses are something new. They are just adding to a long list.

One example of this are several swine flu outbreaks within the last 60 years, with subtypes spilling back and forth between farmed pigs and humans, reassembling and causing many deaths in both.⁷⁰ It is no coincidence that zoonotic diseases (stemming from animals) and associated outbreaks have been significantly and steadily increasing for decades. Zoonotic diseases account for 60 to 80% of all human disease outbreaks.⁷¹

Pigs, in particular, pose a concern as they can host both avian and human influenza strains,⁷² giving the virus DNA the opportunity to reassemble. Authorities are monitoring for this. The farmers themselves are another possibility regarding reassembly.⁷³

A recent analyses has not found any changes in the most common and virulent virus type (H5N1, Clade 2.3.4.4b) in goat or cattle hosts that suggest their infections aided it to adapt better to humans,⁷⁴ and neither has been found in humans⁷⁵yet.

Solutions

Advice by the WHO is in line with current MPI recommendations.^76,77

• Consuming raw or incompletely cooked animal products from areas experiencing outbreaks of avian influenza is high-risk and should be avoided. Likewise, animals who are sick or have died unexpectedly should not be eaten.
• Due to the potential health risks to consumers, including but not limited to H5N1 viruses, raw milk and raw milk products should be avoided.
• Any interactions with dead or sick animals should be avoided.

For consumers of animal products, it does seem at the moment like industrial heat treatment leaves virus strains in the products but no live viruses.⁷⁸

Burying killed animals poses a substantial risk of infectious material being dug up by wildlife⁷⁹ and should be avoided.

Research can be done in cell culture instead of using animals,⁸⁰ with the human cells giving actually relevant results. Laboratory methods can be used instead of animals to study mutations in the virus.⁸¹ Computer modelling is available to predict potential spread via migration and animal agriculture.⁸²

Vaccines are available (at least in the U.S.⁸³ and Europe⁸⁴), and more are being developed⁸⁵ (and tested on animals, sadly) or are in human trials⁸⁶ currently. Potential vaccination against H5N1 will likely follow other flu vaccinations; doing it for every flu season to actually get protection as the viruses are constantly changing. Recent research displayed a bias in the immune system, causing us to likely only develop antibodies against one of the strains in a multi-strain vaccine. They had ideas how we might work around that, and this approach might be useful for a future vaccine covering bird flu strains.⁸⁷

One Health, a worldwide initiative launched in 2008 between the World Health Organization (WHO) and several other health organisations, emphasises the inextricable connection between human, animal and environmental health.⁸⁸ That is generally a good concept, yet falls short of the scientifically evident conclusion:

To actually avoid future pandemics, we need to restructure our food system away from industrial animal agriculture and rethink how we treat our environment.

What can we do?

More people need to understand the connection between animal agriculture and the health risks that come with the industry, for the animals as well as humans. We have more pages on the connection between agriculture and animal experimentation here and here.

At this point, we must also wonder how it can be remotely justified to even talk about reinstating the Live Export trade in Aotearoa.

Summary

Viruses are a natural part of life on Earth, with specific reservoirs—in the case of bird flu viruses: wild birds. They become dangerous when they spread beyond these reservoirs into new territories and species. Currently, the scientific consensus is that H5N1 remains an avian virus without specific adaptations to mammals, including humans. This has been the case for a long time. Outbreaks in mammals are primarily linked to close contact situations, often due to global animal agriculture, and are not exclusively attributed to this subtype. However, we must remain vigilant, as viruses are constantly evolving and each cross-species infection carries the potential to spark a new pandemic. Ideally, for the health of animals, humans, and the environment, humanity will move away from farming animals altogether,⁸⁹ reducing breeding grounds for various zoonotic diseases.