COVID hit the U.S. while my partner and I were back home at a wedding in Kansas. At the time, there were a handful of cases on the coasts, but concerns about the new Virus were drowned out by the busy reception full of hugs and Irish whiskey.

When we saw that dinner was buffet-style, we looked at each other and left the wedding — both of us quietly doing the math as hundreds of guests milled around the room. We settled instead into a far-away booth at a divey Mexican restaurant down the road. I didn’t realize then that this meal would be our last together for many months or that his work and mine were about to change and collide in ways I never expected.

He left early the next morning, concerned that his hospital and others like it were soon to be understaffed and overwhelmed. At the airport, he grabbed his backpack and kissed me on the cheek — 4 months went by and the world changed.

In that time, I took a job at Harvard leading a research project that aimed to scope and analyze the twisting chains of animal commerce that many believe ignited that change — and continue to drive zoonotic disease risk, both in the U.S. and abroad.

While he worked long hours in the COVID ICU, I poured over white papers and interview transcripts trying to understand the forces that push and pull pathogens across the globe and the pathways of animal use that allow those viruses to spill over into humans. As the shape of the problem unfolded before us, our team began to make out the contours of something much larger, and perhaps much darker, than what we first imagined.

Far from being an “over there” problem, animal use in the U.S. takes place on a vast scale, driving new spillover events in which pathogens move from animals into humans. Much of this use is poorly understood, poorly regulated, and happens outside of public view. Many of the same practices that we deem high-risk when they take place elsewhere occur right here in the U.S. as well. We, too, have so-called “wet markets” here — 84 of them in New York City alone — where different species are kept alive in cages and slaughtered on site. We also consume an estimated 1 billion pounds of “bushmeat” each year in the U.S., though we instead refer to this meat as “game.”

Both the scale and diversity of animal use in the U.S. makes the country uniquely vulnerable to zoonotic outbreaks. The U.S. processed 10 billion livestock animals for food in 2022, and remains the largest importer of wildlife in the world, bringing in hundreds of millions of wild animals annually, many without any health or safety checks — some without ever being seen by anyone. These animals go on to live in our backyards and basements, kept as exotic pets, or in research laboratories, roadside Petting Zoos, and elsewhere.

But alongside these large industries exists a vast array of smaller ones, and each carries its own constellation of risks. Many of these we never see, never think about, or never even know about — from camel farms to captive hunting operations, bat guano harvesting to backyard bird production, swap meets and exotic animal auctions, livestock fairs, fur farms, petting zoos, coyote urine producers, and wholesale wildlife dealers who keep thousands of animals, representing dozens of species, together in vast warehouses.

And as our research went on, it became clear that zoonotic outbreaks are not historical events but living threats that change and grow, disappear, and reappear. In 2020, as we looked at the risks posed by wildlife farming, mink on fur farms in Utah began contracting COVID-19. In Michigan, the animals spread a new variant of the virus back to humans. Yet, in some states, these operations don’t even require so much as a license, even though they combine a host of risk factors that make them hotspots for potential outbreaks. In 2022, as we sought to trace the path that mpox took through the exotic pet trade to reach the U.S. for the first time 2 decades earlier, the first cases of a new outbreak started showing up in Massachusetts — stoking painful memories of another, far-more deadly virus (HIV) that originated in animals.

While we spoke with experts about the catastrophic risks of a new influenza pandemic, dead seabirds infected with H5N1 began littering public beaches in what has now become the largest avian influenza outbreak of all time — leaving more than 58 million birds dead on U.S. poultry farms. This virus has spilled over to dozens of species of mammals and to a man in Colorado, who was working to depopulate infected birds at an industrial farm. And as this outbreak grew, it acted like a blacklight illuminating many of the industries we’d been studying and even leading us to new ones. The virus spread through backyard chicken coops, zoos, petting zoos, and live bird markets; it infected the commercial game farms where wild species are raised in captivity by the millions and hunting ranches where they are later released and shot.

Any one of these industries could generate a new pandemic strain of the H5N1 virus, but at present, many are so poorly documented and loosely regulated that we don’t know how many animals they contain, where they are located, and what kinds of diseases these animals might carry.

And if that happens, when that happens, will the risks we take be worth it? This was the question I sat with late into the evenings, waiting for my partner to come home from his shift — exhausted, with mask lines etched into his face.

Those of you reading this know better than most the true loss and cost of the COVID-19 pandemic. You bore witness to this tragedy in a way that many of us outside the medical field can scarcely imagine. And borne from your expertise and experience comes an obligation, as well as an opportunity, to speak out in favor of prevention — to do what you can, what each of us can, to make all of us safer from the countless pandemic threats out there.

Ann Linder, JD, MS, is the associate director of policy & research in the Brooks McCormick Jr. Animal Law & Policy Program at Harvard Law School.