Avian influenza isn’t new. But the most recent outbreak’s rapid and prolific spread is setting off alarm bells.

“Arguably, we are in the age of pandemics.”

It’s a bold statement. And perhaps hyperbolic.

But when someone like Justin Bahl says it, you should probably listen.

“We’ve challenged the environment to an extreme extent. We have increased the number of animals we’re producing domestically for food in an industrial way that requires us to maximize profits and speed. If a disease gets in there…”

The professor of infectious diseases and epidemiology at the University of Georgia trails off, leaving a palpable tension in the air. “We—as a species—are going to let our guard down and sleepwalk into our next pandemic.”

Like thousands of his fellow scientists across the world, Bahl dropped everything when the COVID-19 pandemic hit, temporarily hitting pause on his own work to study the coronavirus, its transmission, and how it evolved from its animal host to infect humans.

Bahl doesn’t have a crystal ball. And like most researchers, you’d be hard-pressed to get him to predict which virus, bacteria, or fungi will cause the world to shut down next. 

But there’s a reason he’s been working on avian influenza for two decades.

A Flu for the Birds

Avian influenza, or “bird flu” as it’s colloquially known, is a bit of a catch-all term. 

There are multiple types of avian influenza, much like human seasonal flus. Different strains of bird flu are common in wild birds, and most of the time, they don’t even make the birds sick. 

In 1997, things changed. A highly pathogenic avian influenza virus first identified in domesticated geese spread to humans working in the poultry industry in Hong Kong. Eighteen people were infected. Six died.

Less than a decade later, the same virus, known as H5N1, reemerged, this time causing widespread outbreaks in poultry farms across Asia.

Then it got into wild birds.

“There’s not much we can do about a viral infection that’s everywhere,” says Nicole Nemeth, an associate professor in the UGA College of Veterinary Medicine and head of the Southeastern Cooperative Wildlife Disease Study’s diagnostic service. Based in the UGA College of Veterinary Medicine, the cooperative provides wildlife disease expertise to state and federal fish and wildlife agencies, including the Georgia Department of Natural Resources.

As wild birds spread the virus around the globe, researchers began detecting new highly pathogenic avian influenza strains. H5N2. H5N6. H5N8. 

In 2014, an outbreak in the U.S. resulted in the destruction of tens of millions of birds. 

Avian flu seemed unstoppable. That is, until it kind of just went away on its own.

“Why did it fade away? We don’t really know,” Nemeth says. 

That outbreak likely lacked the wild bird reservoir needed to sustain the virus, says Bahl, who has a joint appointment in the UGA College of Public Health and the UGA College of Veterinary Medicine. Bahl also serves as the co-lead of the CDC-funded Pathogen Genomics Center of Excellence.

Infected backyard poultry were culled, as were infected commercial flocks. While avian influenza never truly disappeared, reported cases decreased. Things quieted down.

Until 2020.

From One Species to the Next

While one virus raged in the human population, another slowly spread through waterfowl. First in Europe, then in North America. 

Over the next few years, the new strain of H5N1 ripped through multiple wild bird species. Then it hit commercial poultry farms and backyard flocks.

In 2022, the U.S. Department of Agriculture reported something odd. H5N1 was infecting red foxes. And bobcats. And opossums. And mountain lions. 

The list of infected mammals kept growing, with die-offs of every species from domestic cats to tigers, harbor seals to grizzly bears, and bottlenose dolphins to whales.

“The adaptability of this particular virus is phenomenal,” Bahl says. “It might actually have infected a greater diversity of hosts than pretty much any other virus that we know of.”

A scary prospect.

“This is something people should be concerned about,” says S. Mark Tompkins. “The virus evolved in about two years to infect over 100 mammalian species and kill them. That gives the virus the opportunity to change. That in and of itself is concerning.”

Tompkins heads UGA’s Center for Influenza Disease and Emergence Research, one of only six such institutions focusing on the history, transmission, and progression of influenza nationwide funded by the National Institute of Allergy and Infectious Diseases. 

Tompkins was already in touch with the National Institutes of Health and the Food and Drug Administration when reports began circulating about avian influenza gaining a foothold in U.S. dairy cattle. His lab quickly became one of only five to test U.S. dairy supplies for avian influenza on behalf of the FDA.

A Virus on the Move

Why dairy cattle? That’s the question plaguing researchers like Tompkins and Bahl. 

Other species likely became infected through interactions with infected birds or their droppings. Something about the cows, though, appears to be different.

It could be because many of the country’s dairy farms are in the Midwest, directly under the migratory pathways of multiple wild bird species. Maybe their droppings land in the fields, and cows ingest them on grass? 

Infected cows carry high viral loads in their udders. Perhaps the milking machines are passing the virus along.

Or are husbandry issues to blame? Cattle are sold and moved from farm to farm, carrying the risk of potentially spreading disease. Even something as simple as farmers forgetting to change out of their boots after tending to a flock of chickens could bring the virus along for the ride when heading to the cattle ranch.

It could be all of these or none. 

“We don’t know how viruses are getting into poultry farms or cattle farms,” Bahl says.

Preventing the Next Pandemic

Despite the scientific advancements, the federal partnerships, and interdisciplinary scholarship happening on a global scale, avian influenza remains an enigma.

“Maybe we won’t be able to find out the answer as to why this happened or how to prevent it from happening again,” Tompkins says. “The complexity worries me.”

The uncertainty is unnerving for Bahl too. 

“If we know exactly when and where it’s coming in, we should be able to prevent continuous spread,” he says. “We’ve done a pretty good job through depopulation of poultry. If it’s with wild birds, well, it’s much more difficult. 

“But if we can understand the patterns of migration, the timing of spread between populations, incorporating host behavior and climate data, we can actually start predicting when and where viruses might show up. Then we can mitigate a lot of the threats of highly pathogenic avian influenza.”

For now, the disease remains largely in the animal world, says Casey Ritz, a professor of poultry science in the UGA College of Agricultural and Environmental Sciences. Ritz is also a poultry specialist with UGA Cooperative Extension, a statewide resource that provides free, research-based information to Georgians through classes, programs, and general outreach.

Humans can catch it, but it’s rare. In the U.S., only 70 people have contracted avian influenza during the current outbreak. And most of those people worked directly with dairy cattle or poultry.

But three out of every four emerging diseases in people come from animals. And there’s nothing stopping avian influenza from joining that dangerous club.

Disease forecasting, though still in its infancy, may be the key to making Bahl’s dreams a reality. 

With centers dedicated to the ecology of infectious diseases, to tropical and emerging global diseases, to the study of influenza and more, UGA is uniquely positioned to lead that charge. 

‘In for the Long Haul’

As this story goes to print, reports of infected animals are dropping off, a hopeful sign that maybe this strain will peter out for a while like its predecessor. With fewer than 100 people infected, it appears unlikely that this is the next outbreak that will shut the world down. 

But bird flu isn’t going away.

“We might be in for the long haul with this one,” Ritz says. “There’s no easy fix to this, and vigilance is going to be important.”