Factory farms: A pandemic in the making


In March 2009, the first case of a novel H1N1 influenza virus infection was reported in the small community of La Gloria in the Mexican state of Veracruz. The virus quickly spread through Mexico and the United States, and in June 2009 the World Health Organization officially declared it a pandemic. Within a year, the Centers for Disease Control and Prevention (CDC) estimates, it had killed up to 575,400 people worldwide.

Early reports suggested that the source of the outbreak lay in the factory-style pig farms in the area around its epicenter in Veracruz. Subsequent tests, however, traced the genetic lineage of the virus to a strain that had emerged in an industrial hog farm in Newton Grove, North Carolina, in the late 1990s, where it had circulated and evolved among pigs before crossing to humans. 

Most recent pandemics, including the one we’re currently experiencing, have been the result of zoonotic viruses “spilling over” to humans from animals. In many cases, this spillover hasn’t occurred via so-called “exotic” animals in faraway markets, as is believed to have been the case with the new coronavirus, but through domestic livestock. 

Most livestock today are raised in “concentrated animal feeding operations” (CAFOs) – more commonly known as factory farms. In these industrial-scale facilities, the proximity of thousands of genetically similar animals, packed together in unsanitary, overcrowded spaces and vulnerable to disease due to the stress placed on their immune systems by these living conditions, provides the ideal environment for viruses and other pathogens to circulate, mutate, and evolve the ability to cross over to human populations.

Research shows that these farms can act as “amplifiers” for the spillover and spread of viruses. One recent model based on data from hog farms shows that workers at these facilities, being in close proximity to animals and thus at increased risk of contracting a virus, can be a “bridging population” for transmission of diseases from pigs to humans. The study found that a higher percentage of factory farm workers in a given community leads to a higher rate of human influenza cases in that community, concluding that a human influenza epidemic due to a new virus could be amplified in a local community and beyond by the presence of a factory farm nearby. 

Most of the major pandemics of recent decades can ultimately be traced back to birds, bats or other wildlife, but because these creatures are so genetically different from us it’s difficult for viruses to jump directly to humans without some other species acting as an intermediary. Historically this intermediary has often been pigs. Being genetically quite similar to us, and with similar immune systems, pigs are ideal “mixing vessels” in which viruses picked up from other animals are “genetically rearranged” to be able to cross over to human populations. In particular, it’s believed that pigs are the primary source of influenza pandemics, because they can pick up the virus from both birds and humans and act as incubators for new strains that combine genetic traits from both, and thus make the relatively easy jump to humans.

Industrial pig farms have been the source of a range of disease outbreaks over recent years, the 2009 H1N1 outbreak being a case in point. In this instance, the new virus is thought to have arisen from a “reassortment” of bird, swine and human influenza viruses combined with a Eurasian pig flu virus. Similarly, in the 1990s, factory farms were at the epicenter of a deadly Nipah virus outbreak, believed to have been the result of pigs in CAFO operations in Malaysia contracting the virus from bats and passing it on to farm workers, causing an outbreak of fatal encephalitis among pig farmers.

But it’s not just pigs. Studies have indicated that industrial poultry farms can be similarly lethal amplifiers of disease, as was the case with the 2006 HPAI (highly pathogenic avian influenza) outbreak and the H5N1 avian flu in the late 1990s, both of which originated in Chinese poultry farms. Avian flu spreads quickly in chickens and is thought to have been picked up and carried further afield by migratory birds in the vicinity of these farms. The virus is still mutating to this day, and continued outbreaks in industrial poultry farms worldwide – including in Thailand, Nigeria, France, and in just the last couple of months, India and China – are providing new opportunities for the virus to mutate into a form capable of moving even more easily among both animals and humans.

Factory farms are a relatively recent development in agriculture. Until the late twentieth century, most of the world’s food animals were dispersed across numerous diversified small to mid-sized farms growing a mixture of different crops and raising different kinds of livestock. In the space of just a few decades, a combination of unrestrained corporate power, wrongheaded agricultural policy and inadequate environmental and public health regulations – all of which can be remedied if we so choose – has led to a system of intensive, industrialized food production that poses serious risks to both animal and human health. 

COVID-19 is the latest in a growing catalogue of public health disasters stemming directly from humans meddling with wildlife, and it’s right that we should be exploring every avenue to figure out exactly how it emerged and to ensure that nothing like it ever happens again. But while the spotlight is currently trained on animal husbandry practices on the other side of the world, we also need to recognize that our own agricultural systems are creating hotbeds for disease outbreaks, potentially no less devastating than this one, right here on our own doorstep. A growing scientific consensus and a history of painful experience show us that averting future pandemics begins with transitioning away from factory farms and toward means of food production that pose less danger to our environment and our health.

Matt Wellington, U.S. PIRG, contributed to this post.

Photo: Mercy For Animals Canada via Flickr (CC BY 2.0)