Discovering how the bird flu virus degrades in the air around livestock and how engineering solutions can effect that degradation quickly and efficiently are core aims of a new University of Michigan Engineering-led project funded by the U.S. Department of Agriculture. This work could help prevent or mitigate future outbreaks.

Detection of bird flu infection within flocks and herds leads to the mass culling of animals, which disrupts food supply chains. The ongoing outbreak of HPAI H5N1 that began in 2022 in the U.S. has led to the loss of 175 million birds and, as of late 2024, has cost the industry roughly $1.4 billion.

The $2 million grant from the USDA's Animal and Plant Health Inspection Service aims to answer two fundamental questions about bird flu:

• How quickly does the virus that causes bird flu lose its infectivity in the air, specifically air found in enclosed livestock environments?

• What technologies can effectively reduce bird flu's infectivity in those environments?

Herek Clack, U-M associate professor of civil and environmental engineering, will lead the project, conducting tests on how nonthermal plasmas can render aerosols containing the virus that causes bird flu incapable of infecting humans and livestock. His team's approach essentially exposes air to strong electric fields, temporarily creating free electrical charges that damage viruses and render them harmless.

"Both the USDA and the agricultural industry want a playbook-science-based guidelines-for how to operate under the threat of bird flu," Clack said. "We're after a better understanding of how the airborne virus behaves in enclosed livestock operations and what technologies can best protect animals and workers."

How nonthermal plasma inactivates viruses

Previously, Clack and his team developed a plasma reactor capable of reducing the number of infectious viruses in the air by 99.9%. Building on that work, they will test how nonthermal plasma inactivates viruses in air that contains traces of pollutants, such as ammonia, that are common around livestock. 

Clack and his team have previously shown that such air pollutants can, at very low concentrations, inhibit the effectiveness of nonthermal plasmas for inactivating viral aerosols. Under this new grant, they will expand the range of air pollutants tested and explore enhancements to the nonthermal plasma that could counteract those pollutants' effects. Of particular interest is how air pollutants and plasma treatment separately influence the air's pH, a chemical measure related to acidity. 

"A key question we're looking at is, 'What will happen with pH levels-how do they impact the infectivity of the viruses?'" Clack said. "The air pollutants tend to raise the pH in the air, but nonthermal plasma reduces pH."

If part of the plasma's effectiveness depends on lowering the pH of the air, it may not be as effective if the air's pH starts higher.

Measuring normal bird flu virus infectivity loss in air

Allen Haddrell, a research fellow at the University of Bristol in the U.K., will employ a relatively new technology of his own design to answer the question of how long the virus that causes bird flu retains its infectivity in the air. The traditional method for measuring how quickly airborne viruses decay involves filling a cylindrical drum with virus-laden air, then slowly rotating the drum to keep the virus particles in the air. But setup for this method is slow.

"What they miss with that approach is roughly the first 20 minutes of the infectivity decay," Haddrell said. "Consequently, they can get wildly different results. Different research groups can look at the same virus and come to different conclusions."

Haddrell will use a technique developed at the Bristol Aerosol Research Centre.

"We levitate virus-containing droplets into an electrodynamic field," he said. "We expose the population of viruses containing aerosols to different environmental conditions, where we change things like relative humidity or gas composition. 

"After a set period, we deposit the aerosol and measure how much the viral infectivity has changed. We use this approach to measure how different environments affect airborne viral decay. And we use this information to figure out the fundamental drivers of decay."

A better grasp of the decay dynamics associated with the virus that causes bird flu and a proven means of inactivating the virus in ventilation air would give the agricultural industry tools to better deal with the virus's next appearance. But it will also lay the groundwork for an industry response to the next human pandemic.

"During COVID, workers in these enclosed livestock or processing operations were 50 to 70 times more at risk for contracting the virus, according to a GAO report from 2023," Clack said. "It told us those close working conditions were the source of greater risk."

Understanding the decay rate of airborne viruses like those that cause bird flu will help us devise more effective protection for workers and animals from future infectious respiratory diseases.