The interconnected nature of human, animal and environmental health was a recurring theme during the “Emerging Infections From a One Health Lens” session, where speakers examined how pathogens are moving across geographic, environmental and species boundaries, creating new challenges for clinicians, researchers and public health officials.
Melioidosis
Alex Hoffmaster, PhD, chief of the Bacterial and Special Pathogens Branch in the Division of High-Consequence Pathogens and Pathology at the Centers for Disease Control and Prevention, opened the session with an overview of melioidosis, a disease caused by Burkholderia pseudomallei that is increasingly being recognized throughout the Americas.
Known as the “great mimicker,” melioidosis presents in a variety of ways, complicating diagnosis. “About half the cases present as pneumonia,” Dr. Hoffmaster said. Clinical diversity is only part of the challenge. Although culture remains the gold standard for diagnosis, patients are frequently culture-negative at presentation.
“We recommend you culture aggressively with whatever specimens you have available,” he said.
Even when cultures are obtained, laboratory identification can be difficult because automated systems have historically misidentified the organism. While improved diagnostic databases have helped, awareness remains critical, he said.
Transmission can occur through percutaneous exposure, inhalation or ingestion, while person-to-person spread is rare. Diabetes remains the leading risk factor for infection. Although most U.S. cases have been associated with travel, Dr. Hoffmaster emphasized that clinicians should think more broadly.
Evidence increasingly suggests that B. pseudomallei has become established in parts of the Western Hemisphere. Confirmed cases and environmental detections have been reported in Central America, South America, Mexico, Puerto Rico and the U.S. Virgin Islands, while investigations in Mississippi identified the organism in both soil and water samples linked to human infections.
Other investigations have raised questions about how the pathogen persists and spreads. In Georgia, two workers became ill after Hurricane Helene in 2024. Both were infected with strains linked to Southeast Asia, yet CDC investigators also identified closely related isolates collected in the same region during the 1980s.
Dr. Hoffmaster noted research shows hurricanes can contribute to pathogen dispersal.
He also described the extensive investigation of the first known U.S. melioidosis outbreak in 2021. Four patients infected with an identical strain traced to South Asia were ultimately linked to an imported aromatherapy spray sold by Walmart, prompting a nationwide recall.
New World Screwworm
The One Health implications of emerging infectious diseases were also evident in a discussion of New World screwworm, presented by Rebecca Chancey, MD, of CDC’s Division of Parasitic Diseases and Malaria.
While “there are lots of flies that cause myiasis,” New World screwworm differs because its larvae feed on living tissue rather than dead tissue, Dr. Chancey said. Female flies can lay 300 to 400 eggs in wounds or even minor skin breaks, and the resulting larvae may remain in tissue for up to a week.
“It is primarily a pest of livestock, but we know there are human cases,” Dr. Chancey said.
Although New World screwworm was eradicated from the southeastern United States decades ago, it has reemerged in Central America and Mexico. Dr. Chancey said the pace of northward movement has accelerated in recent years.
She noted that illegal trafficking of animals has likely played a major role in that expansion because the flies themselves typically travel relatively short distances.
Human infections are increasing across affected regions. Approximately 2,800 human cases have been reported in Mexico and Central America, including 14 deaths, although Dr. Chancey cautioned that the true burden is likely higher because of underreporting.
The impact has been even more apparent in animals. Recent U.S. detections have involved cattle, sheep, goats, dogs, horses and elk, as well as positive fly traps in Texas and New Mexico. Sterile-fly release programs are now being deployed to slow the spread.
For clinicians, rapid recognition remains essential. Dr. Chancey urged clinicians to report suspected cases promptly. “This is something you don’t want to miss in treating your animal or human patient,” she said.
Avian Influenza
The session concluded with a broader examination of highly pathogenic avian influenza and the challenges of applying a One Health framework to a rapidly evolving global threat.
Carol Cardona, DVM, PhD, the B.S. Pomeroy Chair in Avian Health at the University of Minnesota, traced the spread of H5 viruses from their emergence in Asia in the 1990s to their current global distribution. What began as a disease largely affecting poultry has expanded dramatically in host range and geography.
“We simply have a massive explosion of hosts,” Dr. Cardona said.
Unlike previous outbreaks that were sustained primarily within poultry populations, the current epidemic is being driven by wild birds, she said.
That distinction has major implications for control efforts. Traditional approaches that focus on depopulating infected flocks can reduce transmission within poultry operations, but they cannot eliminate a virus that continues circulating in wildlife.
With more than 202 million birds depopulated and continuing viral evolution driven by reassortment, she argued that a broader systems approach is needed.
Such an approach requires balancing the priorities of human health, animal health and environmental stewardship while acknowledging that those priorities do not always align. The goal of One Health, Dr. Cardona said, is not merely to respond to crises but to create stronger systems for long-term planning, communication and collaboration.
Despite decades of experience with H5 viruses, she acknowledged there are no easy answers for controlling the disease while minimizing economic losses, disruptions to food systems and impacts on animal populations.
Photo: Melioidosis is increasingly being recognized throughout the Americas, according to Alex Hoffmaster, PhD, chief of the Bacterial and Special Pathogens Branch in the Division of High-Consequence Pathogens and Pathology at the Centers for Disease Control and Prevention, who spoke at a Friday session.