Blog written by Julie Hurst, volunteer blog writer

"Growing cattle, pigs or chickens is not the same as making parts for mobile telephones." This damning comment was made by Dr Dirk Pfeiffer, Professor of One Health at City University of Hong Kong, in a swipe at the meat production industry following the recent outbreak of bird flu in the United States. April saw what is thought to be the first instance of mammal-to-human transmission of the virus when a rare form, detected in cattle, was contracted by a farm worker in Texas. And while governments and the poultry sector tend to blame free-living birds for the disease, this detracts from the real reasons behind its origin and spread, which Dr Pfeiffer and others in the scientific community insist are profit maximisation, poor animal management, and our preference for cheap meat. In other words, people.

HOW DID BIRD FLU EVOLVE?

The origin of the virus can be traced back to China's southern Guangdong region. Known for its vast wetlands, the area is well-suited to wild aquatic birds who are recognised hosts of low pathogenic avian flu. This form of the virus occurs naturally – it has been identified in more than 100 free-living bird species worldwide – and causes few, if any, symptoms. But it is when this low pathogenic influenza finds its way into industrial poultry sheds that it can evolve into high pathogenic avian influenza – such as the now renowned H5N1 strain – and in 1996, a farmed goose in China became the world's first bird to be diagnosed with this highly dangerous virus.

High pathogenic bird flu, as its name suggests, is highly contagious and able to kill 90 -100% of a poultry flock within 48 hours. And while free-living birds can and do facilitate its spread, they are actually the victims of the virus, with reported deaths in the tens of thousands and actual numbers thought to be in the millions. As Thijs Kuiken, a comparative pathologist at Erasmus University Medical Centre in the Netherlands, has said, "High pathogenic avian influenza is typically a poultry disease, which doesn't occur in the wild".

WHAT CAUSES THE BIRD FLU VIRUS TO SPREAD?

Essentially, low pathogenic bird flu spreads from wild birds to poultry. In poultry, the low strains mutate into severe high strains, which are then transmitted into free-living bird populations and back again in a vicious cycle. And rather than as a result of direct infection, Thijs Kuiken has warned that "people are the real problem". Firstly, we carry the virus into premises – on shoes and clothing, machinery, and animal feed and bedding; and secondly, by the impact of our farming methods. It's no coincidence that so-called spillovers of the disease between livestock and wildlife have increased as intensive farming has escalated to keep up with our ever-increasing demand for cheap meat. Indeed, the emergence of the H5N1 strain occurred not only alongside the rapid expansion of China's commercial duck and poultry sectors but also due to the industry's growth worldwide. In 1996, there were some 14.7 billion poultry birds globally, primarily chickens, and today, that number has doubled.

WHY IS INTENSIVE FARMING AIDING THE TRANSMISSION OF BIRD FLU?

Intensive poultry production provides the ideal breeding ground for the virus. Thousands of highly stressed birds crammed into vast warehouse-style sheds, 'often wading in their waste', are a constant supply of new hosts through which it can move extremely quickly. Rapid rates of transmission are aided by the fact that the chickens are all genetically similar – they are bred to grow extremely large, extremely quickly – and have weakened immune systems. As a result, as soon as one bird becomes infected, that one quickly infects the rest.

Not surprisingly, these appalling conditions also provide the perfect environment for the emergence of ever more virulent strains, and intensive farming's dependence on huge amounts of soy and cereals for animal feed contributes to this too. This is due to the expansion of agriculture into forests and other wildlife habitats in order to provide the land to grow a vast amount of crops, disrupting ecosystems, reducing biodiversity and thus increasing the risk of pathogen spillover. The consequences of this are what we are currently witnessing in the United States.

WHAT DO WE KNOW ABOUT THE RECENT BIRD FLU OUTBREAK IN THE US?

To date, according to official figures, herds of cattle in ten states have been infected with the H5N1 strain, all lactating dairy cows. They are thought to have been exposed to the virus through infected milking equipment, which is not typically sanitized between each use. And officially there has also been three cases of bird flu spilling over from cows to humans during the outbreak. However, according to Michael Osterholm, director of the Centre for Infectious Disease Research and Policy (CIDRAP), "most" infections are likely to be going undetected. Indeed, it is suspected that the true number of both cattle and human infections in the US is likely to be considerably higher than documented, and that the virus is probably much more geographically widespread than we are led to believe.

Under-reporting is thought to be significant and attributed to a combination of factors, including the remoteness of some locations, a reluctance by workers to seek out health care, a lack of health insurance, concerns about immigration status, and an unwillingness among farmers to have cattle and employees tested for avian flu (testing which remains voluntary). It had also been claimed that many farmers simply weren't 'waving the flag' as unlike poultry farmers, who receive indemnity payments for losses related to culling birds when they find cases, dairy cattle farmers hadn't been compensated for reporting infections in their herds. However, it is hoped that a new $200m government-funded support package will now address this.

Scientists' efforts to shed light on the size of the outbreak and its evolution have been hampered by this lack of information. But it's not only a shortage of data that's caused the problem. The details they received weren't released until almost four weeks after the outbreak was announced. One has to wonder why…

IS BIRD FLU THE NEXT HUMAN PANDEMIC?

It seems clear that a catalogue of human failings is fuelling what is now considered to be a pandemic among animals and birds. High pathogenic avian flu has encircled the globe, even reaching as far as Antarctica, where the first case was detected earlier this year. Since the initial outbreak of the highly infectious H5N1 strain, more than half a billion farmed birds have been slaughtered, millions of wild birds have been killed and at least 26 species of mammal have also caught the virus, including seals, sea lions, red foxes, bears, wild boar, and now cattle.

There is also the very real prospect of a human pandemic to consider. While to date there have been relatively few recorded human infections - 889 between 2003 and1st April 2024 according to the WHO - mortality is extremely high, with more than 50% of people known to have become infected having died. The first human has now died from a related H5N2 strain.

Human greed and self-interest have sparked a situation that cannot simply be solved by trying to address the symptom and not the cause. Increasing farm biosecurity and slaughtering countless numbers of infected animals aren't what's needed if we are to avoid further and more virulent incidents of the disease, yet these knee-jerk reactions continue – an entire flock of chickens at a commercial premises in East Yorkshire was killed following a confirmed outbreak here this past February.

HOW DO WE PREVENT BIRD FLU?

Despite the uncomfortable truth that we are indeed the problem, we can also be the solution. According to Sam Sheppard, professor of microbial genomics and evolution at Oxford University, a move away from intensive livestock farming will reduce the disease risk, a view supported by a United Nations report which states that such practices are actually believed to be responsible for more than 50 percent of zoonotic diseases (those that jump from animals to humans). The authors of an editorial in the Science journal go one step further, stating that we need to move from a diet of animal to plant-based proteins, a call to action that's increasingly being made to counter some, if not all of our most pressing global crises. We may sadly be eating our way towards the next pandemic, and more, but we can also eat our way out of it.

As always,

For the animals.