Wild animals like endangered California condors and even a polar bear have contracted H5N1, highly pathogenic avian influenza (HPAI), or “bird flu.” So have more than 180 other species of wild birds and mammals, including marine mammals and federally protected wildlife. 

Bird flu has led to the euthanizing of more than 90 million poultry in 48 states since 2022 and half a billion globally in the past few years. A newly discovered mutation may significantly increase the risk of harm to animals and people.

A microscopic view of avian influenza particles
This colorized electron microscope image released by the NIAID shows avian influenza A H5N1 virus particles, shown in yellow, grown in Madin-Darby Canine Kidney (MDCK) epithelial cells, shown in blue. Source: CDC/NIAID/AP

The Role of Factory Farming in H5N1 Spread and Mutation

Factory farming, meat overconsumption, and climate change are at the heart of the spread of bird flu. However, the environmental and health threats posed by factory farms too often go unaddressed due to this powerful industry’s ability to evade regulation. 

Confining farmed animals in unnaturally dense populations in industrial facilities causes explosive rates of viral transmission. It also dramatically increases opportunities for mutations that make the virus better adapted to new kinds of hosts, like humans and wild animals.

Hundreds of chickens are squashed together in an indoor barn
Crowded hens in a free-range egg farm in Kazakhstan. Credit: Bogna Wiltowska / We Animals

Human Health Concerns: Dairy Products and Worker Exposure

Most people falling ill have been working with cattle at industrial dairy operations, although there have also been confirmed cases in children in California’s Bay Area, potentially linked to consuming raw milk. 

Bird flu viral particles have been found in dairy products on shelves in 20% of samples tested and in wastewater. The U.S. Department of Agriculture and Centers for Disease Control are leaning heavily on the processes of pasteurization and fully cooking foods like beef and eggs to keep people safe, though the safest and most environmentally responsible route is to avoid these products altogether. 

Calls for Action: Increased Testing and Interagency Coordination

Community and wildlife conservation groups have called on the CDC  to ramp up the federal response to bird flu in factory-farmed dairy cattle, improve testing of farmworkers for exposure to H5N1, and coordinate a data-driven interagency response.

At the time of writing, about a year into this latest outbreak, bird flu is confirmed in 985 cattle herds across 17 states. In California, the nation’s leading producer of dairy, nearly half the herds have been infected. 

A map showing the counties in the USA that have reported avian influenza
Bird flu outbreaks involving commercial poultry facilities, backyard poultry and hobbyist bird flocks in the United States. This data is provided by U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) and is correct as of 1 April 2025. Source - CDC

But it’s hard to know the true scope of the outbreak, and that’s due to an egregious lack of testing and reporting. 

We know from COVID-19 that public data, tracking, and reporting are vital to containing a viral outbreak. Yet agencies are making the same mistake with a slow initial response to H5N1. 

Bird flu may have been circulating in cattle as early as December 2023. There were early warning signs of an outbreak on dairy farms early in 2024. However, the USDA only announced the outbreak in March of that year. By April, the USDA had shared only partial genome data and indicated that some farmers weren’t letting them properly test their herds. State agriculture agencies also appear to have complicated the CDC’s ability to track the spread of the disease.

Climate Change and Biodiversity Loss: Contributing Factors

Climate change is also contributing to biodiversity loss and the rise of disease. A warmer world with degraded ecosystems is ripe for the proliferation of pathogens. The California Condor Recovery Program successfully vaccinated California condors to protect them against HPAI, but of course, this is not a feasible solution to protect all wildlife at risk. Instead, we need to turn to the roots of the problem: habitat loss and animal agriculture. Experts have long warned that factory farms are pandemic incubators, putting everyone at risk.

Dozens of day-old chickens are kept in an orange container. A person is injecting one of them with a vaccine
Day-old chicks are vaccinated with a continuous injection syringe at a hatchery in Poland. Credit: Andrew Skowron / We Animals

‍Preventing the Next Pandemic: Shifting Away From Factory Farming

To prevent avian flu from becoming the next pandemic, agencies should be testing animals and workers — including those at nondairy operations. If this virus takes off in hogs, we may be unprepared for the ensuing crisis. Pigs tend to be better conveyors of disease for human infections. Though recently reported U.S. cases have been mild, the global fatality rate in people from H5N1 infections is high.

Avian influenza has killed millions of farmed and wild animals but isn’t yet widespread in humans. We saw what can happen with COVID-19. Efforts must be strengthened to protect biodiversity and stop the next pandemic. That means shifting away from industries like factory farming.

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