Powys branches of CPRW have been campaigning for years for effective regulation of the intensive livestock industry. Our campaign has targeted the existing planning and regulatory systems which are failing to protect Powys residents from air and water pollution, landscape damage and loss of amenity, issues central to CPRW’s charitable remit. Rural Wales has suffered very badly during this Covid19 pandemic, loss and personal tragedies have been accompanied by huge damage to the rural economy, and way of life. It is now time for Welsh Government to acknowledge that its promotion of intensive livestock farming, so damaging to rural Wales, is also raising the risk of the next pandemic. It is time for Government to take action to move away from the intensive model of livestock farming back to the traditional animal husbandry for which Welsh farmers are rightly famed.

This article looks at the role of intensive livestock farming of poultry and pigs in increasing pandemic risk, and what – urgently – needs to be done to reduce that risk.

If you actually want to create global pandemics, then build factory farms.” Dr. Michael Greger

Zoonotic disease: According to the US Centre for Disease Control and Prevention (CDC) 3 in 4 new human diseases are zoonotic i.e. derived from animals. Many of them, including Covid19, result from the ‘spillover’ of an animal virus which is harmless in its natural host into humans. There are an estimated 1.7 million undiscovered viruses hosted by mammals and birds and any jump into the human population is likely to be driven by human behaviour. For example, spillover can arise from human destruction of wildlife habitat resulting in closer animal/human contact, while industrial livestock farming creates the perfect environment for both the mutation of viruses in the livestock population, and transmission of suitably mutated viruses to humans.

Until the outbreak of Covid19, scientists had been expecting that the next pandemic would be a flu virus, given the prevalence of multiple strains of flu viruses in intensively farmed poultry and pigs, but coronaviruses have also been increasingly emerging and circulating in livestock populations around the world. Three new coronaviruses have emerged in just the last decade in Chinese pig herds. Influenza viruses and coronaviruses are unstable and readily mutate, given the opportunity.

The intensive livestock industry: In 2016 it’s estimated that across the world more than 66 billion chickens were killed for food, and nearly 1.5 billion pigs[i], and the industry is still expanding. In the last 50 years the human population has approximately doubled, but meat consumption has more than quadrupled. The big companies, among them Tyson, Perdue and Cargill, have been exporting the US intensive method of livestock farming around the globe since the early post war period. Huge profits are to be made by a business model which externalises both risk and environmental and public health costs. But this method of farming represents the most profound change in the human/animal relationship in human history, and comes at huge ecological costs.

Standards of welfare differ around the world: for example, in the UK we don’t currently permit the US practices of feeding dead cows to chickens and chicken manure back to cows. But the essence of intensive livestock rearing is the close confinement of large numbers of animals, bred and fed for maximum ‘output’, deprived of many or any opportunities for natural behaviour and activity. Animals are sometimes physically maimed to prevent stress behaviours. They are commonly given prophylactic antibiotic doses as growth promoters and in order to suppress illness that would otherwise arise from these unnatural conditions. As a result, where wild chicken ancestors grew to about two pounds in four months, modern broilers are fattened to more than twice the weight in less than half the time. Compromised animal health and mortality are built into the business model.

Specialist breeding has maximised poultry ‘efficiency’ and genetic diversity is unprofitable: around five egg-laying chicken breeders and five broiler breeder companies supply most of the global intensively reared poultry flock.

Viruses in intensive livestock populations: From a virus’s point of view, the large and frequently replaced populations of genetically similar, immune compromised animals packed close together are exactly what’s needed for efficient spread, mutation and potentially transmission to humans. Pigs, being susceptible to both human and bird flus, can be simultaneously infected with both so providing opportunity for two viruses to reassort genetic material and create a hybrid bird/human flu, such as caused the pandemics of 1957 and 1968. Evolutionary biologist Rob Wallace describes factory farms as ‘the best way to select for the most dangerous pathogens possible’.

Intensive poultry farm

Viruses have taken up this man-made opportunity with increasing alacrity. Incidences of viruses among intensively farmed animal populations are too many to list and are increasing in frequency. For example, in just the last five years there have been more than 200 outbreaks of various strains of highly pathogenic avian flu viruses in the US, resulting in the deaths of more than 50 million chickens and turkeys. Flu viruses and coronaviruses mutate freely and so can adjust their virulence and ability to infect new hosts, and the international meat trade allows previously isolated strains to recombine. Currently considered to pose the greatest threat of human pandemic are the avian flu subtypes H5N1 and H7N9.

H5N1 and H7N9 bird flu: It used to be assumed that a virus in a livestock population could be eliminated by culling. But since 2004 highly pathogenic H5N1 bird flu has been able to harmlessly reinfect globe-trotting wild waterfowl, the original reservoir of bird flu viruses, and is now endemic in the wild population, ready to reinfect domestic poultry at any time[ii]. Since the first human outbreak in 1997, H5N1, originally a mild virus found in migrating ducks, has become a frightening virus which has been described as ‘the most important threat[iii] the world is currently facing. H5N1 has a human mortality rate around 60%: more than 10 times the approximately 5% mortality rate of the 1918 bird flu pandemic and many times the mortality rate of Covid19, estimated at 1-3%. So far, although bird to human transmission has occurred, H5N1 has not achieved effective human to human transmission. Leading public health institutions believe this is only a few mutations away. To quote the WHO: ‘We really can’t scare people enough about H5N1’[iv].

H7N9 has more recently arrived on the scene and first infected humans in China in 2013. With a human mortality rate thought to be around 40%, H7N9 is described by the WHO as ‘an unusually dangerous virus for humans’. Fortunately, this virus too has not yet acquired the means to transmit effectively between humans.

It’s not fanciful to suppose that these or others of the viruses circulating round intensive livestock farms have the potential to cause a pandemic, as the timeline below illustrates.

TIMELINE: pandemics with animal origin since 1918

  • 1918-1919: H1N1 Avian flu pandemic, estimates of 50-100 million dead in three waves of the virus, young adults and pregnant women proving most susceptible. Domestic pigs may have played a role in the transmission of the virus to humans.
  • 1957-8: ‘Asian flu’: H2N2 Avian flu, estimates of 1.1 million dead worldwide
  • 1959- : HIV: First well documented case in 1959, though thought to have emerged in early 20th century, and associated with hunting of chimpanzees. Became widespread in the 1980s and the WHO estimates 32 million dead worldwide.
  • 1968: ‘Hong Kong flu’: H3N2 Avian flu, estimated 1 million dead. Continues to circulate as seasonal influenza A virus.
  • 1998: Nipah virus, a Henipavirus found in fruit bats, first identified in Malaysia infecting pigs and pig farmers. 109 deaths by 1999, and repeated outbreaks across the region since. Though Nipah has as yet only been found in humans in five countries, this virus is listed by WHO as one of the 10 most important pathogens to monitor. Outbreaks have recorded mortality rates of 75%.
  • 2002-3: SARS, Severe Acute Respiratory Syndrome, caused by a coronavirus possibly originating in bats, first appeared in Asia before spreading across Asia, to the Americas and Europe. 774 died.
  • 2009-10: H1N1 (new strain) swine flu, a reassortment of bird, human and swine flu viruses. The first confirmed human case was a 5 year old boy in La Gloria, Mexico, a major centre for intensive pig farms. Within a week, the virus was found in ten countries, and had reached 180 within 4 months. Estimates of 150,000 to 575,000 dead.
  • 2012: MERS, Middle Eastern Respiratory Syndrome, caused by a coronavirus, possibly originating in bats and transferred to humans via camels, first identified in Saudi Arabia. Mortality rate: 3 to 4 in 10.
  • 2014-6: Ebola: Largest outbreak of disease first discovered in 1976. Virus of uncertain origin, possibly originating in bats.
  • 2019-? : Covid19 coronavirus

The next pandemic may well be more virulent than Covid19, may spread more easily from person to person and may target different groups within the population.

Antibiotics and drug-resistant bacteria: The effectiveness of human antibiotics and the future of human medicine as we know it is jeopardised by the regular use of antibiotics on intensively reared livestock. Globally, around 70% of all antimicrobials are used in animals raised for food, mainly to prevent disease and to promote growth rather than to treat sick animals[v]. Colistin, a human antibiotic ‘of last resort’ is only one of many antibiotics which has been commonly used to promote growth and prevent disease arising from poor husbandry.  This exposure to antibiotics enables microbes to establish defences against the drugs used to treat those infected with them. Some non-viral pathogens are already transmissible to humans, like Streptococcus Suis, first identified on pig farms in Holland, which can cause meningitis, sepsis and deafness in people handling infected pork products. There is considerable risk of highly drug-resistant forms of bacterial pathogens emerging from intensive livestock farms to infect the human population. The CDC warned in a major report last year that the post-antibiotic era is already here, and drug-resistant bugs are here[vi], but antibiotics continue to be used in factory farms.

Other human health risks: Further risks to human health arise from processes involved in factory animal farming such as production of fish-meal feed in Peru, or the treatment of workers in meat-packing plants, particularly during the Covid19 outbreak. Air, water and soil pollution carry human health risks, as does the consumption of the nutritionally poor and potentially contaminated meat which is produced.


It’s sometimes argued that factory farms are land efficient and produce food in the quantity and at the price the world needs. While intensive livestock sheds may sit on small plots, vast acreages of arable land, sometimes the other side of the world, are required to produce the feed. Around 40% of global cereal crops are fed to livestock. According to the United Nations Environment Programme these crops, if used as human food, could feed an extra 3.5 billion people. Roughly speaking, 2 kilos of grain are required to produce one kilo of chicken, and a kilo of pork requires 4 kilos of grain. Checkout prices for factory farmed produce don’t reflect the huge environmental and public health costs pushed onto the public purse. Food poverty needs different solutions.


 ‘The best way to survive a pandemic is not to have one in the first place. Dr. Michael Greger

Preparing for a pandemic is essential, but it’s only damage control. Public health is best served by addressing the risk factors themselves.

Scientists and expert bodies such as the World Health Organisation and CDC have been warning of pandemic risks associated with factory farming for decades. In November 2019 the American Public Health Association reiterated its call for a moratorium on any new industrial farms or extensions to existing farms. But the industry has deep pockets and great influence; the world’s politicians are not all listening.

Can the industry be made safe? Industry claims that enclosed facilities can be biosecure don’t take account of roof vents sending airborne pathogens on their way to infect any hosts in the vicinity, nor the likelihood of workers travelling farm to farm carrying disease on their boots or clothing. Even if appropriate vaccines existed and could be manufactured in sufficient quantity, vaccination of growing global poultry flocks against disease could not provide a long term answer, both because of the rapid mutations of many viruses and because the effectiveness of vaccines is in any case reduced where immune function is compromised.

The risks can only be removed with their root causes: which are the numbers, the density and the poor health of animals reared within each factory farm and the proliferation of the farms themselves. In other words, the safest course is to abandon this model of farming altogether. The farms could be destocked entirely, or radically deintensified by reducing the numbers and density of animals, improving their genetic health and diversity, and improving their health and welfare. At the same time, governments should support more sustainable methods of farming and require the factory farm industry to pay its own costs.

Individually, we can campaign for an end to factory farming, for better animal welfare, clearer food labelling and higher food and environmental standards, and, of course, for the industry to bear its own costs. We can also sponsor healthier foods and more sustainable forms of farming by buying less and better meat and animal products, and supporting our local producers.


  • The End of Epidemics, the looming threat to humanity and how to stop it. Dr. Jonathon D. Quick (2018)
  • Spillover, Animal Infections and the Next Human Pandemic. David Quammen (2013)
  • Pandemic, Sonia Shah (2016)
  • Big Farms Make Big Flu. Rob Wallace (2016)
  • Animal Factory, the Looming Threat of Industrial Pig, Dairy and Poultry Farms to Humans and the Environment. David Kirby (2010)
  • How to Survive a Pandemic. Dr. Michael Greger (2020)
  • The Pandemic Century. Mark Honigsbaum (2020)


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[ii] Covid19 has also been detected in other species including mink:

[iii] Julie Louise Gerberding, former director of the U.S. Centers for Disease Control and Prevention. (Fox M. 2005. Bird flu poses ‘ominous’ threat. Toronto Star, February 22, p.AO1.

[iv] Sandman & Lanard, 2005. Bird flu: communicating the risks. Perspectives in Health 10.

[v] ‘Is the next pandemic on our plate?’ Compassion in World Farming 2020

[vi] ‘Antibiotic Resistance Threats in the United States 2019’, CDC