The ongoing outbreak of bird flu has led to the deaths of millions of egg-laying chickens in the US. The deaths that have occurred over the last three months have had significant impact on the prices of eggs, helping to raise them to their highest point in years.

Bird flu cases often surge during the autumn and winter months due to the migratory patterns of waterfowl. During the summer months, these birds are breeding and raising young in northeastern Asia where they interact with other bird species, allowing the virus to spread and mutate. Then, during the colder months, the birds migrate, where they either come into contact with poultry and other captive birds or spread the disease in the feces that they drop along the way.

At the same time, the cooler weather allows the virus to stick around in the environment for longer. During the summer, sunlight and heat kill off the virus if it is exposed on surfaces, but this happens less in the winter.  

Although we have seen cases of bird flu rise during the winter months over the last few years, this winter has been particularly harsh for the agricultural industry in the US, according to CBS News.

In March last year, the virus was confirmed in dairy cattle in Texas, which soon spread to other herds across the US. Its transmission was linked to contaminated raw milk – milk that has not undergone pasteurization, which heats the product to kill any viruses. The disease is thought to have spread across the country through contaminated milk droplets carried on farmers’ clothing, their equipment, and through contact between different animal species.

The chicken crisis has also been unprecedented. CBS reports that more than 20 million egg-laying chickens died from the disease or as a result of culling in the last quarter, despite the country having one of the strongest avian influenza surveillance programs in the world, according to the US Department of Agriculture (USDA).

The disease has impacted all major production systems, including conventional caged birds, cage-free, and certified organic types, the USDA explained in a new report. However, the federal government has spent $1.25 billion helping to compensate farmers for their losses since the outbreak started. The hope is that this support will encourage farmers to report infections and to strengthen and monitor their biosecurity approaches.

In mid-December 2024, bird flu killed 20 big cats at a specialized sanctuary in Washington State as the disease spread to the mammals living there.

But despite the surge in bird flu cases among animal species, confirmed cases among people remain low. At time of writing, the Centers for Disease Control and Prevention (CDC) has reported 66 infection cases since the current outbreak of highly pathogenic H5 avian flu began in the country in 2022. Most of these cases have related to farm workers who have close contact with animals.

However, one individual in Louisiana recently died from the infection.

So while the disease’s threat to humans is still limited, the CDC urges people to take precautions and be vigilant, especially those who work with birds and animals.