Photo: Jo-Anne McArthur / We Animals Media
Avian flu has spread swiftly across farms globally since late 2020, leaving bird populations devastated in its wake and consumers facing higher egg prices. In the United States, the outbreak has resulted in the culling of more than 58.7 million birds across 47 states in a series of more than 830 outbreaks.
The high price of eggs is just one outcome of bird flu. Far more worrying is the possibility that the disease could adapt to human bodies and lead to the next global pandemic. Though eating chicken or eggs is unlikely to lead to illness, experts agree that the pandemic risk of avian flu is real, stemming largely from the way birds are raised on factory farms and the particular breeds of birds that have come to dominate the supply chain.
Bird flu, also known as avian influenza or by the names of its various subtypes such as H5N1, refers to a group of viral infections that exist naturally in aquatic birds in the wild. These viruses also have the potential to spread among other types of wild birds and mammals, domestic fowl, humans, and a variety of other animals.
There are four different categories of influenza: types A, B, C, and D. Avian influenza is categorized as a type A virus. The viruses in this category are different from the other three types in part because they spread more easily between species. Type A influenzas can more readily proliferate and have a higher risk of resulting in a pandemic. Categorization is further defined by the animal species from which the virus originated, for example swine flu or, in this case, avian flu.
Most human cases of avian influenza start with close contact between a human and an infected bird, their carcass, their droppings, or their environment. Infections of people with H5N1 clade 2.3.4.4b, the strain causing the current illness among birds around the world, are rare. Transmission between people has not yet been observed. In February 2023, two human infections of H5N1 occurred in Cambodia, the first in the country since 2014, prompting fears about the widespread bird flu’s potentially rising infectiousness between humans, but these were later attributed to a different form of the virus (clade 2.3.2.1c). However, experts are concerned about future pandemic risk caused by a strain’s capacity to evolve to infect people more easily.
The virus could accomplish this in one of two ways: mutation—in which the virus changes to evade the human immune system’s response, as occurred in the pandemic of 1918—or reassortment—which entails avian flu and a human flu infecting a person at the same time and swapping genes, creating a new and more infectious or virulent strain, as occurred in the pandemics of 1957 and 1968.1
Currently there is no vaccine to protect against contracting bird flu. The seasonal flu vaccine that people are advised to take every year does not prevent the contraction of avian flu.
In humans, the virus can cause no symptoms at all, cause a mild illness, or come with a range of indicators ranging from moderate to severe, among them: headaches, fever, sore throat, fatigue, body aches, and even seizures in particularly acute cases. The infection fatality rate of avian flu is much higher than that of COVID-19.
According to the CDC, since 1997 there have been 890 people diagnosed with H5N1, and of these, about half have died from the illness. A different strain of H5 bird flu, H5N6, was identified in people in China in 2014. Since then 81 people across China and Laos have been diagnosed with it. Among those who were hospitalized for the disease, 30 percent died.
According to the American Veterinary Medical Association, there are several indicators that a flock of birds may be experiencing an outbreak of avian influenza. Symptoms include nasal discharge and sneezing, diarrhea, purpling or swelling of the body, and even sudden and inexplicable death.
On an industrial farm, if avian flu exposure takes place, the entire flock of birds is killed, not just the sick individuals. This is done in an attempt to prevent the spread of disease to other flocks, wild birds, and the people working at the facility. The destruction of entire flocks has contributed to the extremely high number of birds that have been slaughtered as a result of the current avian flu outbreak. Many of these birds are killed in inhumane ways, such as having water-based foam sprayed over them causing them to suffocate, or sealing off their sheds and pumping carbon dioxide into the air. In some instances, birds have also been killed by simply cutting the airflow into their shed and causing temperatures to rise to lethal levels.
Throughout the COVID-19 pandemic, hundreds of millions of people have become familiar with swabbing noses or throats for PCR tests. A similar process, in which a sample is collected from a sick person’s nose or throat, is performed when testing for avian influenza. An alternative way of diagnosing bird flu is by testing phlegm that is coughed up by the sick person.
A person who is suspected of having avian influenza will likely be asked by their doctor to quarantine at home and be given medications to manage the symptoms of the illness. These antiviral medications can help by reducing the severity of the illness while also increasing the chances of survival. Once a diagnosis has been made, there are few options for the ailing, aside from quarantine, prescription antiviral medications, and hoping for the best.
According to the World Health Organization, there have been rare infections of people who consume dishes with raw, infected poultry blood. However, no evidence suggests that avian flu can be contracted from consuming properly prepared chicken products.
No evidence suggests that you can contract avian flu from consuming the eggs of an infected chicken.
While the consumption of chickens and eggs may not place individuals at risk of contracting bird flu, factory farming poultry is a major risk factor in producing the next pandemic. Experts agree that bird flu emerged on industrial poultry farms, and that some bird flu strains have already spread from birds to people. There is consensus among experts that the ongoing industrial farming of poultry makes the emergence of new, more dangerous strains of bird flu—which could more easily spread from bird to humans—far more likely.2 Much of the risk posed by factory-farmed chickens results from their genetic uniformity and the conditions in which they live. The industrial farming status quo gambles with public health. Only with a radical restructuring might raising chickens on farms with a reduced pandemic risk be possible.
While all factory farms present some risk of causing zoonotic disease, the risk produced by chicken farms is the most severe due to the genetic similarity of the birds, the scale and density of production, the close human-animal contact, and the undermining of the birds’ health and immune systems through selective breeding and poor conditions.
At any given time a single barn on one chicken factory farm is likely to contain over 30,000 birds. These birds live in tight quarters that are ideal for disease transmission, and because they have been bred for efficiency from similar stock they have very similar genetics. The people who work directly with the chickens provide the perfect opportunity for a strain of bird flu to make the jump from chickens to humans.3
To reduce the risk of pandemics associated with animal agriculture, particularly chickens, we must change the way we eat and farm. Given that many of our recent pandemics originated from animals, including COVID-19, changing animal agriculture will save not only animal but likely also save human lives.4
The changes start with what we eat. Instead of consuming large amounts of chicken and other poultry products, we must shift diets toward plant-based foods. We recommend that people eat conscientiously, as few animals as possible, ideally none. Since some people will continue to eat animals, though, we need to completely reshape how animals are farmed. The chickens currently raised on commercial farms should be replaced with hardier, slower-growing, heritage birds. Another shift that farms need to make is to take a cue from the “social distancing” required by the COVID-19 pandemic and dramatically reduce the density at which the chickens are housed. These measures would make it more difficult for diseases to spread from bird to bird, reducing the chances of human exposure or a mutation that leads to the next pandemic.
Continuing to raise genetically similar birds by the tens of thousands, tightly packed together in sheds, is a recipe for disaster. Though one individual consuming the eggs and meat of these birds is very unlikely to lead to the spread of disease, the aggregate demand of individuals shapes agricultural production. Failing to shift our dietary habits and farming techniques puts all of us at risk.
Xian Wen Jin and Sherif B.Mossad, “Avian Influenza: An Emerging Pandemic Threat,” Cleveland Clinic Journal of Medicine 72, no. 12 (December 2005), https://www.ccjm.org/content/ccjom/72/12/1129.full.pdf.
Thomas H. C. Sit et al., “Novel Zoonotic Avian Influenza A(H3N8) in Chicken, Hong Kong, China.” Emerging Infectious Diseases 28, no. 10 (October 2022), https://doi.org/10.3201/eid2810.221067
Alyssa Marchese and Alice Hovorka, “Zoonoses Transfer, Factory Farms and Unsustainable Human-Animal Relations,” Sustainability 14, no. 19 (October 2022), https://doi.org/10.3390/su141912806.
Harman S. Sandhu et al., “Pandemic Prevention and Unsustainable Animal-Based Consumption,” Bulletin of the World Health Organization 99, no. 8 (August 2021): 603–605, https://doi.org/10.2471/BLT.20.276238.