Why This Bird Flu Is Different

A University of Maryland-led team of researchers that has been tracking the arrival and progression of a deadly bird flu in North America said in findings released today that slowing its spread requires unprecedented levels of coordination at regional and national scales.

The team also found a shift from seasonal to year-round infections and a far greater impact on wild birds, suggesting that H5N1 will likely become endemic, potentially posing risks to food security and the economy. The paper was published in the journal Conservation Biology.

“We’ve been dealing with low pathogenic avian influenza for decades in the poultry industry, but this is different,” said Jennifer Mullinax, assistant professor in the UMD Department of Environmental Science and Technology and a co-author of the study. Low pathogenic disease is less contagious and easier to contain than the highly pathogenic variety.

“This high pathogenic virus is wiping out everything in numbers that we’ve never seen before,” she said. “This paper illustrates how unprecedented it is, and describes what we think is coming. It’s really a call to arms saying, we can’t afford to address this from our individual silos. Federal agencies, state agencies, the agriculture sector and wildlife management—we are all going to have to deal with this together, because we can’t afford not to.”

The team’s conclusions are based on an analysis of five different data sources that provide information on the incidence of highly pathogenic avian influenza in wild birds and poultry focusing on the USA and Canada as well as a global database from 2014 through early 2023.

The data show H5N1’s progression as it spread from Eurasia to the U.S., where it was first documented in late 2021. By October 2022, the disease had resulted in 31 reported wild bird mass mortalities, accounting for an estimated 33,504 wild bird deaths detected from the virus in the U.S. and Canada. In addition, more than 58 million domestic poultry were infected or had to be culled to limit the spread of infection in the U.S.; that number reached 7 million in Canada.

In 2015, an outbreak of highly pathogenic H5N8 in the U.S. led to the culling of 50 million poultry birds. But the disease was eradicated in North America that same year, largely because it did not seriously impact wild birds, which made containment through culling poultry relatively easy. But H5N1 poses new challenges.

“Unlike H5N8, this disease is heavily impacting wild birds,” said Johanna Harvey, a postdoctoral researcher at UMD and lead author of the study. “It’s difficult to estimate how many birds are truly affected across wild populations, but we're seeing dramatic disease impacts in raptors, sea birds and colonial nesting birds. And we now have the highest amount of poultry loss to avian influenza, so this is a worst-case scenario.”

The data also reveals a shift from a seasonal to a year-round disease. Previous outbreaks of avian influenza—whether low-pathogenic virus that is endemic in the U.S. or highly pathogenic H5N8 in 2015—typically occurred in the fall, which meant farmers could prepare for seasonal outbreaks, cull flocks to halt the spread of disease, and have nearly a full year to recover losses. But this new virus appears sustained throughout the year,.

The study’s co-authors also included Michael Runge and Diann Prosser Ph.D. ’12, research scientists and partners of the Disease Decision Analysis Research Group at the U.S. Geological Survey, Eastern Ecological Science Center. Although declaring a disease endemic is a complicated process, the authors suggest that the U.S. will likely follow patterns seen in Europe where highly pathogenic avian influenza is already being treated as an endemic disease rather than something that can be eradicated.

The research team recommends a management approach based on a method called Structured Decision-Making, which follows a specific process of identifying and bringing together relevant individuals with an interest, expertise or stake in an issue, distinguishing the unknown from the known factors and establishing measurable goals and actions with quantifiable results. The process is much like dealing with a human pandemic.

“Good decision science is what you do when you don’t know what is going to happen next,” said Mullinax, who teaches decision-making science. “This is a novel virus for North American birds, so no one knows if their immune systems will adapt, or how long that will take, or what that will look like. Where do we direct our funds for maximum benefit? Is it a vaccine? How do we track it in wild birds? Do we test the water or the soil? What are the triggers for different actions, and how do we measure if we’re succeeding? These decisions have to be made on multiple scales.”

The paper outlines examples of potential triggers for action, identifying the relevant decision-makers required to coordinate a response and some of the challenges that may come up. The researchers hope their work will bring key players to the table to consider next steps.