Conservation Medicine 16

One Health: Bridging Human, Animal, and Environmental Health.

In a world where infectious diseases leap from wildlife markets to intensive care units, where antibiotic-resistant bacteria migrate from feedlots to hospital wards, and where degraded watersheds undermine the safety of drinking water and food supplies, the idea that human health operates in isolation from its surrounding natural systems is no longer defensible.

That recognition is the foundation of One Health — a framework built on the understanding that the health of people, the health of animals, and the integrity of shared environments are not parallel concerns but deeply entangled ones, and that addressing any one of them effectively requires coordinated action across all three.

What Is One Health?

One Health is both a conceptual framework and an operational approach to the complex, boundary-crossing health challenges that define this century. It draws together human medicine, veterinary science, environmental science, public health, agriculture, and ecology — not as adjacent disciplines that occasionally consult one another, but as genuinely integrated partners in a shared enterprise.

In practice, that integration takes several forms.

1.      It means building surveillance systems capable of detecting zoonotic disease emergence — the transmission of pathogens from animals to humans — before localized outbreaks become regional crises.

2.      It means developing public health policies that address antimicrobial resistance across the full arc of its spread, from agricultural use to clinical consequence, rather than treating each sector's contribution as someone else's problem.

3.      It means investing in collaborative research and education that trains the next generation of health sector professionals to think across the boundaries their disciplines have traditionally maintained.

4.      It means mobilizing coordinated global responses to pandemics, threats to food systems, and the health consequences of climate-driven environmental disruption — responses that no single sector, acting alone, has the capacity to mount.

When One Health functions as designed, the returns are broad and compounding:

·       better health outcomes across human, animal, and ecosystems.

·       reduced costs through prevention rather than crisis response.

·       a more honest reckoning with the ecological interdependence that makes human health possible in the first place.

Why One Health Matters Now.

1.      Emerging Infectious Diseases.

More than seventy percent of emerging infectious diseases in humans originate in animals — HIV/AIDS, Ebola, SARS, MERS, and COVID-19 among them. The conditions driving this pattern are not mysterious: habitat destruction pushes wildlife into closer contact with human settlements and livestock; the illegal wildlife trade concentrates species that would never naturally encounter one another; and intensified agriculture creates dense, stressed animal populations in which pathogens can amplify and mutate. One Health addresses this risk by connecting surveillance of human and animal populations into integrated early warning systems capable of detecting novel threats at the point of emergence, before local spillover events become regional or global crises.

2.      Antimicrobial Resistance.

The overuse and misuse of antibiotics across human medicine, veterinary practice, and industrial agriculture is accelerating a convergence that clinicians and public health scientists have been warning about for decades — a world in which infections that were once routinely treatable become progressively harder to control. Resistance does not respect the boundaries between sectors; resistant organisms move through shared environments, supply chains, and human-animal contact in ways that make any single-sector response insufficient. A One Health approach addresses antimicrobial resistance by promoting responsible prescribing in clinical settings, reducing prophylactic antibiotic use in livestock, and building the coordinated policy architecture that no individual sector has the authority or reach to construct alone.

3.      Climate Change and Environmental Degradation.

Climate change is not a future health threat — it is a present one. Expanding ranges for mosquitoes and ticks are carrying dengue, Lyme disease, and other vector-borne illnesses into populations with no prior exposure and limited immunity. Heat extremes are straining cardiovascular and respiratory systems. Wildfires are degrading air quality across entire regions. And the erosion of biodiversity and ecosystem services — the natural systems that filter water, stabilize soils, and regulate disease — is quietly removing the ecological foundations on which clean air, safe water, and reliable food supplies depend. One Health provides the integrative framework for understanding these cascading risks in their full complexity and for coordinating responses across the sectors — environmental, agricultural, clinical, and public health — that must act in concert if any response is to be adequate.

4.      Food Security and Safety.

The global food system is simultaneously a public health infrastructure and a source of significant health risk. Zoonotic pathogens enter human populations through food animals and supply chains. Contamination events expose large populations to preventable harm. Supply chain disruptions — whether driven by disease, climate events, or geopolitical instability — translate rapidly into nutritional vulnerability. One Health strengthens this system by integrating biosecurity conservation across agricultural and veterinary practice, applying public health standards consistently from farm to table, and grounding food policy in an understanding of the animal, environmental, and human health dimensions that conventional food safety frameworks too often treat in isolation.

Global Recognition and Implementation.

International institutions increasingly endorse the One Health framework:

• World Health Organization (WHO)

• Food and Agriculture Organization (FAO)

• World Organisation for Animal Health (WOAH)

• United Nations Environment Programme (UNEP)

Together, these bodies have launched the Quadripartite One Health Joint Plan of Action (2022–2026) to coordinate, scale, and sustain global efforts @https://wedocs.unep.org/handle/20.500.11822/47013).

Many countries are now integrating One Health into their national health strategies, pandemic preparedness and rapid response plans, and sustainable development goals (SDGs).

One Health in Action.

·       Rwanda's One Health program is among the most institutionally developed on the African continent. The government established its One Health Steering Committee in 2011 — formally bringing together the Ministries of Health, Agriculture, and Environment under a shared governance structure — and has since produced two successive five-year strategic plans, the most recent covering 2021 to 2026, focused on zoonotic disease surveillance, antimicrobial resistance, and multisectoral disease prevention. The program is recognized by WHO, FAO, and CDC as a regional model for operationalizing the One Health approach at national scale.

 ·       Bangladesh's experience with Nipah virus offers a different kind of lesson — one about both the value and the limits of One Health in practice. Recurring Nipah outbreaks, driven by bat-to-human spillover through contaminated date palm sap, prompted Bangladesh to build One Health capacity through joint training of medical, veterinary, and wildlife officers and the development of surveillance and management protocols. Public education campaigns, including national television broadcasts discouraging raw sap consumption, reached broad audiences. But independent assessments have documented persistent gaps — in nationwide surveillance infrastructure, in community knowledge and behavior change, and in the regularity of preventive outreach — that illustrate how much distance can remain between a One Health framework and its full implementation on the ground.

 ·       The United States formalized its One Health infrastructure in the years following COVID-19. The 2023 Consolidated Appropriations Act directed CDC, the Department of Agriculture, and the Department of the Interior to develop a National One Health Framework — the first of its kind at the federal level — which was released in February 2025. The U.S. One Health Coordination Unit, launched in January 2024, brings together twenty-seven federal agencies under shared interagency leadership to coordinate zoonotic disease prevention, detection, and response. The framework identifies avian influenza, Lyme disease, rabies, West Nile virus, and emerging coronaviruses as priority threats requiring sustained cross-sector coordination.

Challenges and the Path Forward.

While the vision of One Health is compelling, barriers to implementation remain:

• Fragmented funding mechanisms.

• Siloed private and public institutions.

• Limited interdisciplinary training.

• Political, regulatory, and governance hurdles.

• Need for stronger community engagement and Indigenous knowledge inclusion.

Still, the momentum is growing—and the stakes are too high to ignore.

To move One Health from theory to practice, we need:

• Cross-sector collaboration at every level—from global institutions to local governments.

• Education and training programs that build systems thinking and transdisciplinary skills.

• Policy frameworks that integrate One Health into climate, agriculture, and healthy public policy.

• Investment in practice and research that spans disciplines and geographies.

A Clarion Call for Integration.

One Health is more than a public health tool. It is a moral imperative and strategic necessity in a world where humans, animals, and ecosystems are deeply interconnected and interdependent.

Bridging our disciplines, breaking down silos, and listening to the natural ecosystems around us may be the most effective—and most human—way to ensure a sustainable, healthy future for all.