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One Health

One Health is an integrated scientific and policy paradigm that recognizes the health of human populations, domestic livestock, wildlife, and ecosystems as an interconnected socio-ecological network, coordinating surveillance across zoonotic spillover interfaces, vector-borne disease ecology, and environmental antimicrobial resistance.

10 min read • Updated October 2026 • Knowledge Wiki • AI-Assisted & Human-Supervised

One Health is a transdisciplinary scientific, ecological, and public health framework that treats the health of human populations, domestic and agricultural animals, free-ranging wildlife, and the shared environment (ecosystems, soils, and watersheds) as a single, dynamically coupled biological system. Rooted in the nineteenth-century comparative pathology of Rudolf Virchow—who coined the term zoonosis in 1855 and declared that "between animal and human medicine there are no dividing lines—nor should there be"—and modernized into "One Medicine" by veterinary epidemiologist Calvin W. Schwabe in 1964, the contemporary One Health paradigm was formally codified in the 2004 "Manhattan Principles" convened by the Wildlife Conservation Society (WCS) at Rockefeller University and institutionalized globally through the Quadripartite Alliance of the World Health Organization (WHO), the Food and Agriculture Organization (FAO), the World Organisation for Animal Health (WOAH, formerly OIE), and the United Nations Environment Programme (UNEP). Because 60.3% of all emerging infectious diseases (EIDs) in humans are zoonoses—and 71.8% of those zoonotic emergences originate in wildlife (Jones et al., 2008)—and because agricultural and environmental reservoirs drive the global evolution of antimicrobial resistance, One Health replaces siloed clinical medicine with upstream ecological surveillance across land-use boundaries, wildlife-livestock interfaces, and climate-sensitive vector habitats (Schwabe, 1984; Jones et al., 2008; Karesh et al., 2012; Destoumieux-Garzón et al., 2018).

Historical Evolution: From Virchow's Zoonosis (1855) to the Manhattan Principles (2004) and Quadripartite (2022)

  1. Rudolf Virchow and Comparative Pathology (1855): While investigating the parasitic nematode Trichinella spiralis cycling between swine and humans in Prussia, German pathologist Rudolf Virchow established that infectious and metabolic processes operate across vertebrate species boundaries without a medical divide.
  2. William Osler and Calvin W. Schwabe's "One Medicine" (1964, 1984): At the University of California, Davis, veterinary parasitologist Calvin W. Schwabe founded the first department of epidemiology and preventive medicine inside a veterinary school and published Veterinary Medicine and Human Health (1964; 3rd ed. 1984), demonstrating how pastoralist Dinka communities in Sudan integrated human and cattle medicine and how zoonotic hydatidosis (Echinococcus granulosus), brucellosis, and bovine tuberculosis could only be controlled by treating livestock and human hosts simultaneously.
  3. The 2004 Manhattan Principles ("One World, One Health"): Following the consecutive shocks of H5N1 highly pathogenic avian influenza (1997–2003), Nipah virus (1998–1999), West Nile virus in North America (1999), and SARS-CoV-1 (2002–2003), the Wildlife Conservation Society brought together human physicians, veterinarians, and conservation ecologists in New York on September 29, 2004, formulating twelve Manhattan Principles (updated by the 2019 Berlin Principles on One Health) that explicitly added ecosystem integrity and wildlife biodiversity conservation as the third pillar alongside human and veterinary medicine (Cook et al., 2004; Gruetzmacher et al., 2021).
  4. The WHO–FAO–WOAH–UNEP Quadripartite Joint Plan of Action (2022–2026): In March 2022, UNEP formally joined the Tripartite of WHO, FAO, and WOAH to create the Quadripartite, defining One Health through the One Health High-Level Expert Panel (OHHLEP) across six operational tracks: laboratory/surveillance capacity, emerging zoonotic spillover reduction, endemic zoonotic and neglected tropical diseases, food safety, antimicrobial stewardship, and environmental integration (OHHLEP et al., 2022).

The Ecological Mechanics of Zoonotic Spillover and the "Dilution Effect"

Why has the rate of emerging zoonotic disease outbreaks quadrupled per decade since 1940 (Jones et al., 2008)? In a landmark 2017 synthesis in Nature Reviews Microbiology, Raina K. Plowright and colleagues modeled zoonotic spillover as a series of hierarchical ecological, immunological, and behavioral barriers (Reservoir Distribution × Reservoir Density × Pathogen Prevalence × Shedding Intensity × Environmental Survival × Human Exposure × Within-Host Susceptibility): only when time-varying gaps align across every layer simultaneously (the "Swiss-cheese model of spillover") does a wildlife pathogen cross into a human index patient (Plowright et al., 2017).

Anthropogenic ecosystem perturbations systematically widen these gaps across four classic One Health disease systems:

One Health Disease SystemWildlife Reservoir → Amplifying Bridge Host → Human InterfaceEcological / Land-Use Perturbation Driving EmergenceIntegrated One Health Intervention (Superior to Human-Only Medicine)
Nipah Virus (Henipavirus, Malaysia 1998–1999 & Bangladesh 2001–Present)Pteropus fruit bats (flying foxes) → intensive commercial domestic pigs (Malaysia) or raw date-palm sap pots (Bangladesh) → pig farmers / sap drinkers (case fatality 40%–75%)Deforestation + Agricultural Intensification: Clearing Dipterocarp rainforest in Malaysia + planting mango orchards directly overhanging open-sided industrial pigsties attracted starving Pteropus bats, which dropped virus-contaminated chewed fruit and urine into pig troughs (Chua et al., 2000; Pulliam et al., 2012).Removing fruit trees from pig farm perimeters in Malaysia permanently ended pig-borne Nipah; in Bangladesh, fitting low-cost bamboo skirts (bana) over date-palm sap collection clay pots blocks nocturnal Pteropus bat licking/urination without harming bats or sap harvesters (Khan et al., 2012).
Hendra Virus (Henipavirus, Australia 1994–Present)Pteropus flying foxes → pasture horses → equine veterinarians and trainers (case fatality 57%)Winter Habitat Loss & Nutritional Stress in Bats: Clearing native Eucalyptus winter-flowering forests forces Pteropus bats into suburban horse paddocks while nutritional stress elevates bat cortisol and urinary viral shedding pulses (Plowright et al., 2015).Equine Hendra Vaccination (Equivac HeV, 2012) + restoring native winter-flowering Eucalyptus habitats to prevent bat nutritional stress and suburban foraging spillover.
Rabies (Lyssavirus, Global Endemic Zoonosis)Free-roaming domestic dogs (>99% of human transmission) and wild carnivores (foxes, raccoons, bats) → human bite victims (~59,000 human deaths/year)Unvaccinated peri-urban free-roaming dog populations below the 70% herd immunity threshold.Mass Canine Vaccination (≥70% dog coverage) + oral rabies vaccine (ORV) baits for wild foxes/raccoons costs <10% of the cumulative cost of human post-exposure prophylaxis (PEP) alone and eliminates rabies in both dogs and humans (Hampson et al., 2009; Zinsstag et al., 2007).
Lyme Disease (Borrelia burgdorferi) & the Biodiversity "Dilution Effect"White-footed mouse (Peromyscus leucopus, reservoir competence ~90%) + blacklegged tick (Ixodes scapularis) → suburban humansForest Fragmentation & Predator Loss: Fragmenting oak-maple forests into <2-hectare suburban woodlots extirpates predators and low-competence mammalian/avian hosts (opossums, squirrels, shrews, which groom off ticks and infect <15% of feeding larvae), leaving hyper-abundant white-footed mice to amplify nymphal tick infection prevalence (Ostfeld & Keesing, 2000).Maintaining contiguous forest patches and vertebrate host diversity (the "dilution effect", Keesing et al., 2010) buffers nymphal tick infection rates alongside landscape tick management.
Rift Valley Fever Virus (Phlebovirus, East Africa)Aedes (floodwater transovarial reservoir) & Culex mosquitoes → cattle, sheep, goats, camels (causing 90%–100% neonatal abortion storms) → pastoralists and abattoir workersEl Niño–Southern Oscillation (ENSO) extreme rainfall anomalies flood East African dambo depressions, hatching millions of transovarially infected Aedes eggs.Satellite NDVI + Sea-Surface Temperature Early Warning (Anyamba et al., 2009) forecasts Rift Valley Fever risk 2 to 5 months in advance, triggering pre-emptive livestock vaccination before mosquito amplification reaches humans.

The Environmental Resistome and One Health Antimicrobial Resistance (AMR)

Over 70% of medically important antimicrobials by tonnage globally are administered not to human patients, but to food-producing livestock, poultry, and aquaculture (often for group metaphylaxis or sub-therapeutic growth promotion; Van Boeckel et al., 2015). Because animal gut microbiomes, manure-fertilized agricultural soils, hospital sewage effluents, and municipal rivers exchange mobile genetic elements (IncX4, IncI2, IncFII plasmids, integrons, and transposons) via horizontal gene transfer across ecological compartments, antimicrobial resistance is an archetypal One Health problem (Robinson et al., 2016; Larsson & Flach, 2022):

  • Discovery of Plasmid-Mediated Colistin Resistance (mcr-1, Liu et al., 2016, Lancet Infectious Diseases): For decades, the polymyxin antibiotic colistin was sparsely used in human hospitals (reserved as a toxic "last-resort" drug against carbapenem-resistant Klebsiella and Acinetobacter), where all known human resistance was chromosomal and non-transferable. However, thousands of tons of cheap colistin sulfate were mixed annually into swine and poultry feed across Asia and Europe. In November 2015, Yi-Yun Liu, Jian-Hua Liu, Timothy R. Walsh, and colleagues discovered the first plasmid-borne colistin resistance gene (mcr-1, encoding a phosphoethanolamine transferase) on an IncI2 plasmid in Escherichia coli isolated from intensivly farmed pigs, retail pork/chicken meat (15% positive), and hospitalized human patients in China. Within months of the One Health alert, China and the European Union banned colistin as a livestock growth promoter, causing mcr-1 prevalence in pigs and humans to fall by >75% (Shen et al., 2020; see Antimicrobial Stewardship).
  • Triazole Antifungal Resistance in Clinical Aspergillus fumigatus (TR34/L98H): Similarly, the widespread spraying of agricultural demethylase-inhibitor (DMI / azole) fungicides on flower bulbs and cereal crops selects in compost heaps for Aspergillus fumigatus spores carrying tandem-repeat promoter duplications (TR34/L98H and TR46/Y121F/T289A in cyp51A), which are then inhaled by immunocompromised human patients—causing fatal pan-azole-resistant invasive aspergillosis in patients who have never previously received medical antifungal therapy (Verweij et al., 2009; Fisher et al., 2018).

References

  1. Schwabe, C. W. (1984). Veterinary Medicine and Human Health (3rd ed.). Williams & Wilkins, Baltimore.
  2. Ostfeld, R. S., & Keesing, F. (2000). Biodiversity and disease risk: The case of Lyme disease. Conservation Biology, 14(3), 722–728. https://doi.org/10.1046/j.1523-1739.2000.99014.x
  3. Jones, K. E., Patel, N. G., Levy, M. A., Storeygard, A., Balk, D., Gittleman, J. L., & Daszak, P. (2008). Global trends in emerging infectious diseases. Nature, 451(7181), 990–993. https://doi.org/10.1038/nature06536
  4. Keesing, F., Belden, L. K., Daszak, P., Dobson, A., Harvell, C. D., Holt, R. D., Hudson, P., Jolles, A., Jones, K. E., Mitchell, C. E., Myers, S. S., Bogich, T., & Ostfeld, R. S. (2010). Impacts of biodiversity on the emergence and transmission of infectious diseases. Nature, 468(7324), 647–652. https://doi.org/10.1038/nature09575
  5. Liu, Y.-Y., Wang, Y., Walsh, T. R., Yi, L.-X., Zhang, R., Spencer, J., Doi, Y., Tian, G., Dong, B., Huang, X., Yu, L.-F., Gu, D., Ren, H., Chen, X., Lv, L., He, D., Zhou, H., Liang, Z., Liu, J.-H., & Shen, J. (2016). Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: A microbiological and molecular biological study. The Lancet Infectious Diseases, 16(2), 161–168. https://doi.org/10.1016/S1473-3099(15)00424-700424-7)
  6. Plowright, R. K., Parrish, C. R., McCallum, H., Hudson, P. J., Ko, A. I., Graham, A. L., & Lloyd-Smith, J. O. (2017). Pathways to zoonotic spillover. Nature Reviews Microbiology, 15(8), 502–510. https://doi.org/10.1038/nrmicro.2017.45
  7. One Health High-Level Expert Panel (OHHLEP), Adisasmito, W. B., Almuhairi, S., Behravesh, C. B., Bilivogui, P., Bukachi, S. A., Casas, N., Cediel Becerra, N., Charron, D. F., Chaudhary, A., Ciacci Zanella, J. R., Cunningham, A. A., Dar, O., Debnath, N., Dungu, B., Farag, E., Gao, G. F., Hayman, D. T. S., Khaitsa, M., … Zhou, L. (2022). One Health: A new definition for a sustainable and healthy future. PLOS Pathogens, 18(6), e1010537. https://doi.org/10.1371/journal.ppat.1010537
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