German chancellor Otto von Bismarck is alleged to have challenged one of his critics to a duel in 1865. According to the apocryphal tale, it was left to the critic, a pathologist with an understanding of the disease links between humans and farmed animals, to select the arms. His weapon of choice? Meat—two pork sausages, identical except that one was infested with the potentially lethal parasite Trichinella. Bismarck could choose which sausage to eat, and his opponent would eat the other. The pathologist won by default. Bismarck recognized the power of the weapon wielded against him, and declined the contest.
More recently, another political power experienced defeat by meat. In February, the Chinese government, finally aware that the wildlife trade’s exorbitant costs have far exceeded its profits, has likewise opted to back away from potentially lethal meat by issuing a permanent ban on the consumption and trade of wild animals. Unfortunately, the ban has come too late. The novel coronavirus, with its suspected source in bats, via pangolins, is believed to have emerged at one of China’s wild animal markets. COVID-19, the acute respiratory disease caused by the virus, has spread around the globe, killing thousands, infecting hundreds of thousands, and costing the global economy trillions.
China’s wild animal markets have long been identified as optimal sites for the emergence of zoonotic viruses with pandemic potential. Stressed animals, immunologically compromised and crowded together in unhygienic conditions, create ideal conditions for the propagation of disease. Activities related to the captivity, handling, transport, slaughter, and consumption of those animals enable diseases to jump to humans. That is precisely what transpired with the 2003 SARS epidemic that infected over 8,000 people, killed 774, and cost the global economy an estimated $40 billion. Civet cats at a wildlife market in Guangdong were identified as the likely vector for transmission of the SARS virus to humans. COVID-19 has already far exceeded the toll of the 2003 SARS outbreak, in both lives and dollars.
SARS and COVID-19 are but two of a series of infectious diseases that have emerged in the human pursuit of meat. Ebola, which has claimed over 13,000 human lives since 2014, has been traced to fruit bats and primates butchered for food. In 1998, the Nipah virus jumped to humans from fruit bats via intensively farmed pigs in Malaysia and killed over half of the humans infected. Measles, responsible for the deaths of millions since its emergence in antiquity, is believed to have originated from a virus in sheep and goats that spilled over to the human population through the process of domestication. HIV, the virus that causes AIDS, was first identified in chimpanzees in West Africa in 1989, and jumped to humans likely through the hunting, butchering, and/or consumption of HIV-infected primates. AIDS, to date, has killed over 32 million people.
The pattern is sobering: the human quest for meat functions as a key driver of the emergence of deadly infectious diseases that kill countless human and nonhuman animals.
Considering the toll, and the ongoing threat to lives and livelihoods posed by COVID-19, it’s worth asking whether the conditions that led to its emergence exist elsewhere. The answer is a resounding yes: conditions conducive to the emergence and spread of virulent pathogens exist in industrialized animal farming operations. Ninety-nine percent of farmed animals in the U.S. come from factory farms. Globally, the figure is 90 percent. The vast majority of meat, dairy, and eggs consumed today come from operations in which billions of cows, pigs, chickens, ducks, goats, sheep, and other immunologically-compromised animals are confined in cramped, unhygienic conditions, and often transported long distances. These operations have been identified as hot spots for the cross-infection of diseases and the mutation of viruses, some with pandemic potential.
Avian influenza, or “bird flu,” is another case in point. Humans have more in common with chickens than most realize, namely a susceptibility to infection with similar viruses. Human pandemics can arise when a strain of the avian influenza virus is transmitted from its source in wild aquatic birds to farmed chickens. A strain of avian influenza caused the 1918 Spanish Flu pandemic that killed 50 to 100 million humans. Tens of thousands of wounded WWI soldiers had gathered in crowded, unhygienic army camps on the Western Front, in close proximity to pig farms and duck, geese, and chicken markets; the circumstances resulted in cross-species transmission of the virus. The demobilization of troops at the end of the war served as the means of dispersing the virus around the globe. Those same pandemic-producing conditions currently exist in industrialized animal farming operations, the main difference being that in 1918, the soldiers functioned as the warehoused chickens through which the virus simmered and then propagated.
Avian influenza viruses are especially dangerous because some strains infect not only birds but also other mammals. When two or more strains of the virus infect the same cell in, say, a pig, a chicken, or a human, the animal or human host acts as a “mixing vessel”—like a cocktail shaker—in which the different strains undergo a process of “reassortment.” The various strains combine to create “novel”—new—strains of infectious disease with pandemic potential. When an avian influenza virus infected farmed pigs, it evolved to produce the H1N1 strain of swine flu, itself a combination of four different viruses from three different species—pigs, birds, and humans. The resulting 1957 Asian Flu pandemic and the 1968 Hong Kong Flu pandemic each caused between one and four million human deaths; the 2009 H1N1 Swine Flu epidemic killed almost 300,000 people. These figures do not include the numbers of animal deaths, which far exceed the human toll. The African Swine Fever virus currently ravaging pig farming operations in China, for example, has led to the death of millions of pigs, many culled by brutal means. The same virus has led to the culling of almost six million pigs in Vietnam in the past year alone. The mandatory killing of farmed animals wherever contagions emerge—whether the animals are infected or not—is not limited to Asia. More than 6.5 million cows, pigs, and sheep were culled in Britain in 2001 during the foot-and-mouth disease epidemic. The repeated, worldwide, infection-induced, mass culling of farmed animals should itself serve as a grave warning sign of a dangerously unhealthy industry, whether one is concerned solely for the wellbeing of one’s own species or for that of others. The viruses that periodically trigger such mass killings continue to combine and mutate, creating novel, potentially lethal diseases to which no one is immune.
Numerous studies demonstrate how intensive animal farming increases the risk of pandemics. Research shows that confined animal feeding operations amplify novel influenza strains and that large-scale commercial animal farms increase the risk of outbreaks and transmission of zoonotic disease, function to maintain and disperse highly virulent strains of influenza and increase the frequency and scale of highly pathogenic outbreaks. It also shows that factory farm-induced deforestation and rampant antibiotic use heighten risk of the emergence of novel diseases. Intensive animal farming unquestionably poses a grave, pandemic-level threat to human and animal health. A 2017 study found that the speed with which new strains of influenza are emerging has increased since 2000, raising the likelihood of pandemics. In the present, grim context of yet another global pandemic precipitated by the human demand for meat, we’ve largely chosen to remain willfully ignorant of the dangers posed by the source of the vast majority of that meat: factory farms.
Evolutionary ecologist Rob Wallace, author of Big Farms Make Big Flu, argues that a factory farm-spawned pandemic is not just possible; it’s probable. “Agribusiness,” he writes, “backed by state power at home and abroad, is now working as much with influenza as against it.” Dr. Michael Greger, author of How Not to Die and Bird Flu: A Virus of Our Own Hatching, calls factory farming a “perfect storm environment” for “super-strains” of infectious diseases. “If you actually want to create global pandemics,” he says, “then build factory farms.” Some may consider such perspectives to be extreme, but they are echoed by mainstream voices. In 2008, the Pew Commission, in its report on industrial farm animal production in America, warned of the “unacceptable” public health risks posed by industrialized animal agriculture. Public health professionals have long been aware of the dangers. In 2003, an editorial in the American Journal of Public Health advocated for an end to factory farming, explicitly acknowledging that killing animals for food—especially via intensive animal agriculture—increases the likelihood of epidemics. The author of that prescient article, Dr. David Benatar, wrote: “Those who consume animals not only harm those animals and endanger themselves, but they also threaten the well-being of other humans who currently or will later inhabit the planet…It is time for humans to remove their heads from the sand and recognize the risk to themselves that can arise from their maltreatment of other species.”
In China, before the COVID-19 outbreak led authorities to announce the closure of the wildlife trade, the industry was valued at over $74 billion. Critics, aware of the trade’s potential to unleash virulent infectious diseases, have for years complained that government policy has been hijacked by commercial interests. It took an epidemic and near-shutdown of the Chinese economy to precipitate a ban on the consumption and trade of wildlife. The conditions that triggered the emergence of COVID-19 exist in plain sight on factory farms. Shouldn’t governments take action before the emergence of another, possibly deadlier, epidemic, rather than after? The economic interests of intensive animal farming operations—not to mention our own appetites for flesh—continue to eclipse the imperatives of public health. If policymakers are serious about preventing pandemics rather than reacting to the carnage after the fact, then it’s time to do with factory farms what China did with the wildlife trade—shut them down altogether.
Correction: A previous version of this article claimed that the Chinese government had announced it would permanently ban the wildlife markets suspected to be at the center of the COVID-19 pandemic. While the government did agree to ban the hunting, trading, transporting, and consumption of wildlife in the wake of the novel coronavirus, a permanent ban on wet markets is not currently in effect.