A brief history of avian flu and its spread
Stories about avian flu have dominated agricultural news in the US over the past year. The virus has had massive mortality impacts on both poultry and wild bird populations.
There have been two major introductions of the current strain, H5N1, into North America. The first was in 2014 on the Pacific coast, and was relatively small. The current outbreak has infected over 6000 wild birds, and spread via the Atlantic coast due to the virus’s expanding epicenter.
The epicenter expanded first from east Asia, then in recent years across different areas of Europe and Africa. This spread into Europe allowed for easier movement into North America via migrating birds. The H5N1 strain is particularly prevalent in waterfowl as many survive the virus, allowing it to further spread.
In a recent press briefing, Nichola Hill, an assistant professor of biology at University of Massachusetts, emphasized the importance of monitoring the virus in wild populations.
“The first detections in the US was in North Carolina concurrently in January 2022. And this occurred in hunted wild ducks. So after introduction, the virus really spread from the Atlantic coast westward across the US, and is now being detected in all 50 states, including Alaska,” explained Hill.
Of the 1000 bird species found in the United States, over 150 of them have been infected with H5N1, including California Condors, and the virus has spread to domesticated poultry and some wild mammals.
The USDA runs an extensive surveillance program of the virus and there is potential for vaccination however some major roadblocks remain. While there has been some spread in wild mammalian populations, risk in humans is still low.
“So, we haven't seen anything that's bringing it close to crossing over and being a human pandemic at this stage,” Hill said.
Essentially, researchers are not seeing the mutation patterns that are likely to cause crossover into humans.
For more information on the history of avian flu, Andrew Ramey and collaborators came out with their article, “Highly pathogenic avian influenza is an emerging disease threat to wild birds in North America” in 2022.