Wild Birds Are Driving the Current US Bird Flu Outbreak

By Deborah Stull

Since late 2021, a panzootic, or "a pandemic in animals," of highly pathogenic bird flu variant H5N1 has devastated wild birds, agriculture, and mammals. Unlike previous outbreaks, aggressive culling of domestic birds has not contained it, and the viruses continue to infect a broad range of species, including wild birds and mammals rarely affected before, suggesting that transmission patterns have shifted since 2022.

Now, in a new study looking at how these viruses were introduced and spread in North America, Louise H. Moncla from the School of Veterinary Medicine and her team have found that wild birds are critical drivers of the ongoing bird flu outbreak in the United States. Their findings are published in Nature.

Highly pathogenic avian influenza (HPAI) viruses—those responsible for bird flu outbreaks—continue to pose challenges for human and animal health.

"The picture for HPAI influenza has really changed for North America and the U.S. in the last couple of years," says Moncla. "This used to be a virus that primarily circulated in Asia, Northern Africa, and domestic birds. But in more recent years, we've seen increasing outbreaks across Europe, associated with wild birds, and since 2022, we've also had similar outbreaks in our North American birds."