What One Health and planetary health mean

One Health connects human, animal and environmental health through collaboration across sectors. Planetary health focuses on how changes in Earth's natural systems affect human health and well-being.

Definitions and history

One Health has been described by WHO as an approach to programmes, policies, legislation and research in which sectors communicate and work together for better public health outcomes, including zoonosis control. ¹ The CDC definition quoted in a 2022 account emphasised collaboration across disciplines and local, regional, national and global levels, recognising the interconnection of people, animals, plants and their shared environment. ²

Planetary health investigates links between Earth's natural systems and human well-being, including the effects of climate change and resource depletion on infectious disease and malnutrition. ³ It brings health sciences together with natural and physical sciences. ⁴ Its concerns include water use, soil degradation, undernutrition, biodiversity loss and climate change, which can reinforce one another. ⁵ By 2019, named subdisciplines included planetary paediatrics, planetary epidemiology and planetary preventive medicine. ⁶

The ideas behind One Health predate its current name. ^{7, 1, 2} Calvin Schwabe's term “One Medicine” dates to 1964, while nineteenth-century discussions already linked animal and human medicine. ^{7, 1, 2} In the early 2000s, BSE, SARS and avian influenza intensified the need for collaboration among veterinarians, doctors and health authorities. ² A US One Health Initiative Task Force was created in 2007, and WHO, FAO, OIE, UNICEF and the World Bank were among the organisations developing a One World, One Health framework in 2008. ²

The same work can carry different labels, including health promotion, ecosystem health, EcoHealth, planetary health, global health, sustainable development or environmental health. ⁸ A 2026 practitioner critique argued that the widening use of One Health had made its meaning inconsistent: a method, field, perspective or reframing of older work. ^{9, 10} That critique proposed intergenerational and interspecies health equity as its organising principle: protecting one species today should not compromise future generations' or other species' health needs. ¹¹

Collaboration and the focus of the work

One proposed taxonomy distinguishes veterinary public health from systems approaches, then separates each by low or high diversity of collaborators. ¹² Veterinary public health manages animal health or animal environments to protect people, while systems approaches consider the connected ecosystem. ¹² Three reasons for collaborating are an inability to address a challenge alone, shared concerns across sectors, and making limited funding go further by sharing resources and knowledge. ¹³

A rabies-suspect animal can connect a veterinary clinician, an agricultural laboratory, public health services and a physician assessing human exposure. ¹³ This illustrates veterinary public health with relatively low collaborator diversity, while antimicrobial-resistance prevention requires collaboration across many uses of animals. ^{13, 8} Wildlife conservation supporting rural food security illustrates a systems approach with greater collaborator diversity. ¹³

The 2026 critique described One Health literature as concentrated on veterinary public health, with systems work often labelled ecosystem health, EcoHealth or planetary health. ⁸ A literature review presented with that critique found that the vast majority of papers described disease problems, almost all of these infectious and almost all of those zoonotic, with very few concerned with protecting health. ^{14, 15} A second review described in 2026 examined twenty years of wildlife-trade spillover work across six languages. ^{15, 16} It found changes in behaviour and action but no project systematically evaluated to show a reduction in health risk. ¹⁶ The critique also questioned equity where animals are killed to protect people, using the culling of chickens to reduce influenza risk as an example. ¹²

Health as capacity and assets

One proposed definition of health extends beyond absence of disease to three qualities. ^{14, 17}

1. Meeting daily needs, including food, water, shelter or suitable habitat.
2. Having the capacity to cope with challenges, such as a deer's reserves for winter, a farmer's financial reserves for an outbreak or society's health infrastructure for a catastrophe.
3. Meeting evolved or social expectations, such as a migratory species having habitat along its route, or expectations about an animal's production.

^{14, 17}

A related wildlife-health model considers daily needs, the physical environment, social interactions, biological endowment, human expectations and direct mortality pressures. ^{18, 19} Natural and social capital, capabilities and relationships between people, places and societies together shape the circumstances in which health is possible. ^{16, 20}

Institutions and shared risks

WHO collects information on human health and monitors the global health situation; the World Organisation for Animal Health performs a corresponding role for animals. ^{21, 22} In 2010, WHO, FAO and the World Organisation for Animal Health, then OIE, produced a Tripartite Concept Note to support integrated work at the human–animal–ecosystem interface. ^{23, 24} By 2026, the Quadripartite also included the United Nations Environment Programme and described integration across human, animal and environmental health and levels of society. ^{10, 25}

Shared health consequences extend beyond infections transmissible to humans. ²⁶ Animal epidemics such as foot-and-mouth disease and African swine fever can threaten human food security through economic loss and disruption of animal production. ²⁶ Communication among veterinarians, doctors, epidemiologists and veterinary pharmaceutical groups can support both food safety and food security. ²⁶

Complex problems and prevention upstream

One framework distinguishes simple, complicated, complex and wicked problems by whether effective responses are known and whether people agree on the desired outcome. ^{27, 28} Technical difficulty alone does not define complexity in this framework; brain surgery is used as an example of a demanding task with an agreed purpose and known response. ²⁸ Climate change instead involves uncertainty and disagreement about what should happen. ²⁸

Planetary-health problems can cross boundaries of authority, expertise, budgets and values, with unclear causes, solutions or even definitions of the problem. ²⁹ A systems critique argues that such problems require changing trajectories rather than expecting a single intervention to remove them. ^{29, 30} Living organisms face several challenges and draw on several assets at once; changing one problem can change others through their connections. ^{27, 11} Studying an isolated pathogen or pollutant can therefore miss those relationships. ^{27, 20}

The proposed upstream response is to create healthier socio-ecological circumstances rather than concentrate only on downstream events and risk factors. ^{31, 32} A Canadian bat-health programme responding to white-nose syndrome asked how survivors could recover, thrive and reproduce, rather than focusing only on the fungus. ³³ A marine-mammal programme similarly questioned returning rehabilitated animals to unhealthy environments. ¹⁹

Preparation for surprise distinguishes failures of observation from consequences of complex systems. ³⁴ Not knowing to look for a threat, or missing its signal, calls for broader awareness, more contacts and more sources of information. ³⁴ Unintended consequences of interactions and previously inconceivable events instead require resilience and the capacity to cope with what could not be anticipated. ^{34, 18}

Shared settings and planetary harm reduction

A settings approach treats the “one” as a shared place rather than a single disease. ^{35, 36} It asks how populations can access resources, have their voices heard, sustain the assets of that place and participate in mediating conflicting goals. ³⁶ For a northern Canadian bison population, such planning had to consider resource extraction, Indigenous rights, cattle trade and biodiversity together. ³⁵

Planetary harm reduction is a proposed analogy with drug-policy harm reduction, applied to dependence on growth, consumption and fossil fuels. ^{37, 38} It uses four complementary responses rather than relying on elimination alone. ³⁸

1. Eliminate use where possible.
2. Reduce use by providing alternatives.
3. Increase the safety of continued use.
4. Mitigate harms that occur.

³⁸

The proposal combines healthier circumstances with an implementation agenda that acts on available knowledge and asks what works for whom, where and how. ^{38, 39} It favours adapting action to local realities and different ways of knowing, rather than exporting one country's approach. ^{39, 40} Its emphasis is on collaborative help and enabling action rather than ownership of a label. ^{41, 42} It also calls for changes in policy, training, perspectives and practice so that One Health can address future challenges. ⁴²