Trend AnalysisInterdisciplinary

One Health: The Human-Animal-Environmental Nexus

Approximately 75% of emerging infectious diseases are zoonoticโ€”they jump from animals to humans. The One Health approach integrates human medicine, veterinary science, and environmental health into a unified surveillance and response framework. Post-COVID, this is no longer aspirational; it is operational necessity.

By Sean K.S. Shin
This blog summarizes research trends based on published paper abstracts. Specific numbers or findings may contain inaccuracies. For scholarly rigor, always consult the original papers cited in each post.

Why It Matters

COVID-19 was a zoonotic disease. So was Ebola, MERS, SARS, avian influenza, and monkeypox. The pattern is consistent: roughly three-quarters of emerging infectious diseases originate in animals before crossing to humans. Each crossing event occurs at the interface where human activityโ€”deforestation, intensive livestock farming, wildlife trade, urbanizationโ€”brings people into closer contact with animal reservoirs.

The One Health approach recognizes that human health, animal health, and environmental health are not separate domains managed by separate ministriesโ€”they are interconnected components of a single system. A veterinarian monitoring antibiotic-resistant bacteria in livestock, a public health official tracking respiratory illness in a farming community, and an ecologist documenting habitat loss in the same region are all observing different facets of the same causal chain.

Despite decades of advocacy, One Health has historically been more conceptual than operational. Siloed institutions, incompatible data systems, and separate funding streams have kept human, animal, and environmental surveillance fragmented. The post-COVID period has created both the political will and the practical urgency to change thisโ€”and the 2024-2025 literature documents the frameworks being built.

The Science

A Holistic Surveillance Framework

Singh et al. (2024), with 58 citations, propose a comprehensive One Health surveillance framework that integrates environmental, animal, and human health determinants. Their framework goes beyond simply combining three data streams; it models the causal pathways through which environmental changes (deforestation, climate shifts) alter animal disease dynamics, which in turn create spillover risks for human populations.

The framework identifies critical surveillance nodesโ€”points in the causal chain where monitoring yields the most early warning value. For example: monitoring antimicrobial resistance (AMR) in wastewater downstream from livestock operations provides earlier warning of AMR emergence than waiting for clinical cases in human hospitals. Similarly, tracking wildlife population stress indicators (cortisol levels, migration changes) can signal ecosystem disruptions that precede zoonotic spillover events.

The practical architecture involves three surveillance layers: environmental monitoring (water quality, soil contamination, habitat fragmentation), animal health monitoring (livestock disease, wildlife population health), and human health monitoring (clinical cases, seroprevalence surveys). Machine learning models then integrate these layers to generate risk scores for specific geographic areas.

WASH Integration with One Health

Dickin et al. (2025), with 5 citations, address a surprisingly underexplored connection: water, sanitation, and hygiene (WASH) interventions have traditionally focused on human fecal contamination, largely ignoring animal feces as a disease transmission pathway. In low- and middle-income countries where humans and livestock share living spaces, animal fecal contamination of water sources is a majorโ€”and largely unaddressedโ€”driver of diarrheal disease and zoonotic infection.

The study documents how re-evaluating WASH through a One Health lens changes intervention design. Traditional latrines solve the human waste problem but do nothing about the livestock waste problem. One Health WASH interventions add animal waste management, livestock housing design, and water source protection from animal access to the standard WASH package.

This integration is operationally challenging: WASH programs sit in health ministries, while livestock management sits in agriculture ministries. One Health WASH requires cross-ministerial coordination that existing governance structures often cannot deliver.

Regional Best Practices

Schiller et al. (2025), with 1 citation, document One Health best practices specifically for the Eastern Mediterranean Regionโ€”an area with diverse health system capacities, active zoonotic disease threats (brucellosis, leishmaniasis, avian influenza), and complex geopolitical challenges that complicate cross-border surveillance.

Their analysis identifies what works: national One Health platforms that bring together human health, veterinary, and environmental agencies under a formal coordination mechanism; joint investigation teams that respond to zoonotic disease outbreaks as integrated units rather than separate disciplinary responses; and shared laboratory networks that can test human, animal, and environmental samples with comparable methods.

AMR as a One Health Case Study

Eissa et al. (2025), with 1 citation, demonstrate the One Health approach through a specific case: tracking multidrug-resistant Klebsiella pneumoniae across cattle, horses, and humans in Egypt. By sampling the same bacterial species from animals and humans in the same geographic area, they trace the transmission and resistance patterns that connect agricultural antibiotic use to human clinical infections.

Their findings confirm what One Health theory predicts: resistance genes circulate freely between animal and human bacterial populations. Antibiotic use in livestock selects for resistance that subsequently appears in human infectionsโ€”a causal chain invisible to any single-sector surveillance system.

One Health Surveillance Architecture

<
LayerMonitoring TargetEarly Warning Value
EnvironmentalWastewater AMR, habitat fragmentation, climate anomaliesHighest (months-years lead time)
AnimalLivestock disease, wildlife stress indicators, AMR in farm animalsHigh (weeks-months lead time)
HumanClinical cases, seroprevalence, hospital AMR dataLow (reactive, not predictive)
IntegratedCross-layer risk scoring via ML modelsOptimal (combines all signals)

What To Watch

The operational implementation of One Health is accelerating through two mechanisms: the WHO-FAO-UNEP-WOAH Quadripartite Joint Plan of Action provides the global governance framework, while national One Health platforms (now established in over 70 countries) provide the operational infrastructure. Watch for the integration of genomic surveillanceโ€”whole-genome sequencing of pathogens from human, animal, and environmental samplesโ€”into routine One Health monitoring. This technology makes transmission chain tracking precise enough to guide specific interventions. The intersection of One Health and climate change is the emerging frontier: as climate disruptions alter wildlife migration, vector habitats, and agricultural practices, the zoonotic spillover risk landscape is changing faster than traditional surveillance systems can track.

Explore related work through ORAA ResearchBrain.

References (4)

[1] Singh, S., Sharma, P., & Pal, N. (2024). Holistic One Health Surveillance Framework: Synergizing Environmental, Animal, and Human Determinants. ACS Infectious Diseases.
[2] Dickin, S., Dagerskog, L., & Dione, M. (2025). Towards a one health approach to WASH to tackle zoonotic disease. PLOS Water, 4(1), e0000376.
[3] Schiller, A., Saidouni, A., & Mahrous, H. (2025). One Health best practices for addressing health threats at the humanโ€“animalโ€“environment interface, with focus on the Eastern Mediterranean Region. Transactions of the Royal Society of Tropical Medicine and Hygiene.
[4] Eissa, N., Salman, M., & Younes, A. (2025). One health approach on zoonotic multidrug-resistant Klebsiella pneumoniae in Egyptian cattle, horses, and humans. Open Veterinary Journal, 15(9).

Explore this topic deeper

Search 290M+ papers, detect research gaps, and find what hasn't been studied yet.

Click to remove unwanted keywords

Search 7 keywords โ†’