As climate change and human activity push wildlife and their diseases into new places, the risk of zoonotic diseases, which spread from animals to humans, steadily grows. These diseases demand serious attention—they can spark pandemics like COVID-19, disrupt food supplies, strain healthcare systems, and cause major economic damage.
School of Public Health (SPH) experts agree that addressing these pressing threats requires a One Health approach, which acknowledges the interdependent nature of human, animal, and environmental health. Relying on expertise from veterinarians, physicians, researchers, and practitioners in a wide range of disciplines, One Health emphasizes community engagement, enhancing surveillance and diagnostics, and advocating for sustained funding to build preparedness. Fortunately, SPH faculty are uniquely positioned to collaborate across disciplines and contexts to unravel these complex, interconnected webs of human-animal disease transmission and mitigate their potentially devastating effects nationwide and globally.
Not just for the birds anymore
For more than 20 years, avian influenza, commonly known as bird flu, has been moving across the world. First appearing in Southeast Asia and then hopping continents, this virus followed the migratory patterns of ducks and geese across Asia, Africa, and into the Western Hemisphere.
“The public needs to be aware that influenza viruses are always changing,” says Jeff Bender, a professor and public health veterinary expert at SPH. Viruses evolve and build their ability to infect as they go. The bird flu’s unique ability to do so has made it a particularly challenging target for experts working to manage its spread. “Ducks and geese are the main movers and shakers of the virus,” Bender says. “However, the virus has been adapting to affecting a broader range of birds, as well as mammals.” The disease’s growing geographic range and adaptability pose significant challenges for health authorities.
When a virus infects multiple species, it’s more prone to mutations, making it more difficult to control and a bigger threat to public health, food production, and economies. Traditional containment methods, such as culling sick birds, are less effective when the disease finds a foothold in numerous species.
The latest bird flu outbreak was first detected in dairy cows, after jumping from birds, in March 2024. It has since spread to major poultry and dairy farms, driving up grocery prices, sparking fears of an egg shortage, and posing a human health risk with the first documented transmissions to humans from dairy cows.
Bender and his team at SPH are closely monitoring the flu’s genetic code to track its mutations and gauge how rapidly it’s spreading. With this information, scientists could help develop vaccines and enhance food security.
To help achieve these aims, Bender’s team collaborates with researchers and a diagnostic lab at the UMN College of Veterinary Medicine (CVM), as well as wildlife centers, agricultural workers, and health authorities to track the disease across various species and locations. Bender says One Health is critical to combatting the spread of bird flu. “We need to identify new and better ways to control and to think about avian influenza,” he says, “and our partnerships and collaborations have been key for developing those.”
Ticks on the move
When it comes to spreading disease, one tiny-but-mighty bug packs a wallop. “Ticks are an ever-present problem that nearly everyone is exposed to, especially in Minnesota,” says Jon Oliver, an SPH associate professor. Still, Oliver says, “Compared to mosquito-borne illnesses, the study of tick-borne diseases is still in its infancy.” He and his colleagues focus their research on understanding how these sneaky skin clingers become such powerful disease carriers, and how to combat their infections.
Ticks lie in wait on vegetation to latch onto a passing person or animal. Once attached, they feed for days and transfer viruses, bacteria, or parasites directly into the host’s blood. Some tick-borne conditions are permanent, with no medication available to reverse them, such as alpha-gal syndrome, which causes an allergy to red meat. But the true heavyweight champion of tick-borne illnesses is Lyme disease. It’s one of the most common infectious diseases in the U.S., with about 400,000 cases reported each year. In some parts of Minnesota, nearly 50% of adult ticks carry the bacteria.
Although Lyme disease is rarely fatal, it can lead to serious health issues. Lyme disease symptoms are often hard to detect at first, and untreated infections can lead to long-term conditions, including arthritis and nervous system problems like Bell’s palsy.
Lyme disease is primarily transmitted by deer ticks, which thrive in humid, forested areas. Over the last 30 years, Oliver says, the range of deer ticks has expanded, and infection rates have climbed. Climate change has led to milder winters, allowing ticks embedded in their deer or rodent hosts to move farther north. Warmer average temperatures are also helping them survive and reproduce at higher rates. Meanwhile, growing deer and rodent populations provide a surplus of food and habitats for ticks to flourish.
But, according to Oliver, there is good news: “I think at this point, a Lyme disease vaccine is likely. There’s already a highly effective vaccine for dogs. There’s no reason that we can’t have a highly effective human vaccine for Lyme disease, or for any of these other tick-borne diseases.”
Plus, surveillance techniques are rapidly improving. Traditional testing methods are highly sensitive but very specific, typically detecting only well-known viruses and bacteria. But Oliver says new tick-borne pathogens arise regularly. He and his team are collaborating with the CVM to develop a novel testing approach that analyzes whole strands of DNA from both ticks and pathogens. This more detailed method allows them to test for known pathogens while also identifying new ones. “I think we will be getting a lot more information on obscure diseases coming out of the woods,” he says.
Tackling a global disease
Although often referred to as a tropical disease, leptospirosis occurs worldwide. Primarily transmitted by rodents, it is dangerously underdiagnosed and underreported—adding to the difficulty of protecting the communities that are most impacted. “We’re probably just seeing the tip of the iceberg,” says Associate Professor Claudia Muñoz-Zanzi when talking about case reports.
Leptospirosis spreads from animals to people through urine. Mainly cycling through rodents and other mammals such as livestock and companion animals, it contaminates soil and water in both rural and semi-urban areas. It also appears as sporadic cases or clusters in urban areas and has caused major outbreaks in tropical cities. Humans mostly get infected through exposure to contaminated environments, but direct contact with infected animals—common in farming or slaughterhouse work—is also a risk. “So leptospirosis really spans all kinds of transmission pathways,” says Muñoz-Zanzi, adding that rising temperatures and more frequent flooding can amplify its spread into human spaces.
Leptospirosis can cause serious reproductive issues in cattle and pigs, including pregnancy loss and infertility. According to Muñoz-Zanzi, these problems directly affect farmers’ livelihoods and global food security. While vaccines for leptospirosis exist, they are often costly and not highly effective, making them inaccessible to many producers.
Muñoz-Zanzi’s research tackles leptospirosis from several angles, starting with understanding transmission pathways leading to human infection. She studies how environmental factors like landscape, weather, and flooding drive leptospirosis transmission, especially in particularly vulnerable regions in Latin America, Southeast Asia, and Puerto Rico. Her research also revealed how the bacteria is present in the environment and flooding increases exposure to the disease.
Additionally, she addresses challenges in diagnosis and surveillance, working on projects to improve case detection, data quality, and prevention strategies worldwide. For example, Muñoz-Zanzi has been leading efforts to produce leptospirosis surveillance guidelines for the PanAmerican Health Organization and the Food and Agriculture Organization, in addition to exploring community-led interventions such as rodent control, particularly in low-resource settings.
Some communities suffer more than others due to a legacy of poverty, inadequate infrastructure, policy gaps, and climate impacts. “[Tropical zoonotic diseases are] a classic One Health issue, and we’re still not where we need to be, even after COVID put One Health in the spotlight,” she says. Her work builds an integrated approach, advocating for greater surveillance, education, policy intervention, and community engagement to control this dangerous, underresearched, disease.
Prions: The new frontier of infectious disease
Originally identified in Colorado in 1967, chronic wasting disease (CWD)—a very contagious, fatal, neurodegenerative disease that mostly infects deer, elk, and moose—has now been documented in 36 U.S. states and five other countries. While no human cases of chronic wasting disease have been identified, scientists are increasingly worried about the potential for CWD to “spill over”— or cross the species barrier — into humans or agricultural species. Although the risk of human transmission is currently considered low, experts warn this could change as strains evolve and the disease expands into new species, making a coordinated, forward-thinking response all the more urgent. Currently, preparedness efforts are constrained by limited resources and inconsistent disease surveillance.
CWD causes dramatic weight loss, weakness, confusion, and ultimately, the death of the animal. There is no vaccine or treatment, and the disease is always fatal to infected animals. CWD spreads through prions—rogue proteins that harm the nervous systems of humans and various wildlife. They can spread directly from animal to animal or lie in wait in the environment for years. Prions are also responsible for mad cow disease, which did spill over into humans and led to over 200 deaths.
“Since we began working on a CWD risk report in 2023, concerns about a CWD prion spillover from cervids to other animal species and humans have only continued to grow in importance, and we’re simply not prepared should a species jump happen,” says Michael Osterholm, Regents Professor and the director of the Center for Infectious Disease Research and Policy (CIDRAP).
CIDRAP gathered 67 experts to create its groundbreaking report on spillover risks and response strategies—covering funding, partnerships, surveillance, and disposal—to guide health officials, wildlife managers, and policymakers. According to Russ Mason, co-chair of CIDRAP’s CWD Contingency Project’s wildlife working group, “This is the first time in my experience that a multidisciplinary and truly One Health approach has been taken towards chronic wasting disease.”
The report outlines nine key recommendations to help prepare for a potential CWD spillover, from securing multiyear funding and strengthening partnerships to improving surveillance and disposal methods. It also highlights the need for robust outreach to primary care doctors and more comprehensive prion-disease monitoring across wildlife, agricultural, and human health sectors.
Clearly, zoonotic diseases pose an urgent and expanding threat to global health, food security, and economies. To reduce these risks, sustained research, widespread public education, and forward-thinking policies are essential. “But we are in a political system where funding for global health is being cut,” says Muñoz-Zanzi. “The most vulnerable suffer the most because they live in environments perfectly suited for these diseases. It’s not just poverty—it’s where people live, and there are no easy fixes.”
The School of Public Health provides a unique, collaborative structure in place to tackle these interwoven issues. Muñoz-Zanzi says, “The School of Public Health is a great place for this kind of research. I feel supported by colleagues who understand the work. It’s rare to have a university with the expertise across public health, medicine, and veterinary medicine.” Together, these experts have the potential to build the knowledge and tools necessary to protect populations worldwide.
