Over the last few decades, hundreds of human pathogens have emerged at a rate unprecedented in human history. Emerged from where? Mostly from animals, says Dr Michael Greger in our first Surge guest blog. Published as part of the Not If, But When campaign.

We’re changing the way animals live on a global scale. As I discuss in my book How to Survive a Pandemic, the AIDS virus is blamed on the killing of chimpanzees by the African bushmeat trade, and SARS and COVID-19 have been traced back to the exotic wild animal trade and live animal wet markets in Asia. Mad cow disease emerged because we turned natural herbivores like cows and sheep into carnivores and cannibals by feeding them slaughterhouse waste, blood, and manure. Our last pandemic, a swine flu in 2009, didn’t arise from some backwater wet market in Asia; it was largely made-in-the-USA on industrial US pig operations. Thankfully, swine flu only resulted in only about a half-million deaths.

The last time a bird flu jumped species and spread easily from human to human, it triggered the deadliest plague in history, the 1918 flu pandemic that killed 50 million people. Evidence now suggests that all pandemic influenza viruses—in fact all human and mammalian flu viruses in general—owe their origins to avian influenza, and we now have bird flu viruses like H5N1 and H7N9 poised to kill millions around the world should they lock in the necessary mutations to spread easily from human to human.

In this new age of emerging diseases, there are billions of feathered and curly-tailed test tubes intensively confined in factory farms for viruses to incubate and mutate within. Thousands or even tens of thousands of animals are typically overcrowded in massive, filthy sheds, living beak-to-beak or snout-to-snout atop their own waste. The sheer numbers of animals, the overcrowding, the lack of fresh air and sunlight, the stress crippling their immune systems, and the ammonia from decomposing waste burning their lungs—put all these factors together and you have a Perfect Storm environment for the emergence and spread of new influenza superstrains.

The question is not if, but when the next pandemic will strike. At this very moment, there are bird flu viruses circulating around half the globe with unprecedented human lethality, killing more than half of their human victims.

We may be one bushmeat meal away from the next HIV, one pangolin plate away from the next killer coronavirus, and one factory farm away from the next deadly flu. Along with human culpability, though, comes hope. If changes in human behaviour can cause new plagues, then changes in human behaviour may prevent them in the future.

A recent Neuroepidemiology editorial by the editor-in-chief entitled What the COVID-19 Crisis Is Telling Humanity concluded:

“Intensive confinement of animals in factory farm operations should be discontinued worldwide for the sake of animals, humans, and the environment, and we should rapidly evolve to eating other forms of protein that are safer for humans, including plant-based meat alternatives and cultured meat (produced by culturing animal cells).”

Michael Greger MD FACLM is a physician, New York Times bestselling author, and internationally recognised speaker on nutrition, food safety, and public health issues. A founding member and Fellow of the American College of Lifestyle Medicine, Dr Greger is licensed as a general practitioner specialising in clinical nutrition. He is a graduate of the Cornell University School of Agriculture and Tufts University School of Medicine. In 2017, Dr Greger was honoured with the ACLM Lifestyle Medicine Trailblazer Award and became a diplomat of the American Board of Lifestyle Medicine.