Introduction
In recent years, the world has witnessed an alarming rise in emerging and re-emerging infectious diseases — from COVID-19 and Nipah to Dengue, Zika, and Monkeypox.
These outbreaks are not isolated biological accidents; they are deeply connected to how humans interact with animals and the environment.
The One Health approach, which recognizes that the health of people, animals, and the planet are inseparable, has never been more
relevant.
Adding to this complexity is climate change, which acts as a silent amplifier — altering disease patterns, expanding vector habitats, and reshaping ecosystems in ways that favor the emergence of new pathogens.
Together, these forces are redefining the global landscape of infectious diseases.
What Is the One Health Concept?
One Health is a collaborative, multisectoral, and transdisciplinary approach that aims to achieve optimal health outcomes by recognizing the interconnection between humans, animals, plants, and their shared environment.
The idea is not new — it was first recognized by Rudolf Virchow in the 19th century, who coined the term “zoonosis.”
However, it gained global prominence after multiple zoonotic outbreaks such as SARS (2003), H1N1 influenza (2009), Ebola, and COVID-19, which collectively highlighted that 70–80% of emerging infectious diseases (EIDs) originate from animals.
The World Health Organization (WHO), FAO, OIE (now WOAH), and UNEP have now institutionalized One Health collaborations to prevent, detect, and respond to zoonotic threats through shared surveillance, laboratory capacity, and coordinated policies.
Climate Change: The New Catalyst for Disease Emergence
Climate change is not just an environmental issue — it’s a public health emergency.
Rising global temperatures, erratic rainfall, melting glaciers, and deforestation are disrupting ecosystems and driving pathogens into new territories.
1. Vector-borne Diseases:
Mosquitoes like Aedes aegypti and Anopheles are expanding their range due to warming climates, bringing Dengue, Zika, Chikungunya, and Malaria to previously non-endemic regions — even to hill states of India like Himachal and Uttarakhand.
2. Water-borne and Food-borne Diseases:
Heavy rainfall and flooding lead to contamination of drinking water, increasing outbreaks of cholera, leptospirosis, and hepatitis E. Warmer oceans promote algal blooms and seafoodborne toxins.
3. Wildlife Migration and Habitat Loss:
Deforestation, agricultural expansion, and urban sprawl are forcing wildlife closer to human settlements. This interface — as seen with bats and pigs in Nipah virus outbreaks — creates new opportunities for zoonotic spillovers.
4. Antimicrobial Resistance (AMR):
Rising temperatures accelerate bacterial growth and gene exchange, worsening antibiotic resistance. Agricultural misuse of antibiotics in livestock adds another layer to this ecological crisis.
Emerging Infectious Diseases in the Climate Era
The link between environmental disruption and infectious disease emergence is no longer hypothetical.
Let’s explore some examples from the 21st century:
COVID-19:
Believed to have originated from wildlife, COVID-19 demonstrated how global travel and urbanization can transform a local zoonotic spillover into a global pandemic within weeks.
Nipah Virus:
First identified in Malaysia, now recurring in India, particularly Kerala. Changes in fruiting patterns of trees due to temperature shifts have altered bat behavior, increasing human contact and risk.
Chikungunya and Dengue:
Once seasonal diseases, they now persist year-round in many parts of India. The Aedes mosquito thrives in warmer and more humid conditions caused by climate variability.
Avian Influenza:
The intensification of poultry farming and migratory bird movements under changing climate conditions have created hotspots for influenza evolution and reassortment.
These examples illustrate that pathogens exploit ecological disruption. Whether it’s landuse change, unplanned urbanization, or changing rainfall patterns, the result is the same — an increased risk of spillover and spread.
The Indian Perspective
India, with its vast biodiversity, dense population, and agricultural dependency, is highly vulnerable to One Health threats.
The National One Health Mission, initiated under the Department of Biotechnology and ICMR, aims to build integrated surveillance systems across human, animal, and environmental sectors.
The ICMR-NIV and NCDC have enhanced laboratory capacity for zoonotic disease detection.
State-level responses to zoonoses like leptospirosis in Gujarat, Kyasanur Forest Disease in Karnataka, and Nipah in Kerala showcase both progress and the need for sustained coordination.
Climate-linked diseases like Dengue, Scrub Typhus, and Malaria are spreading to new geographies, while livestock diseases such as Lumpy Skin Disease and Avian Flu continue to affect farmers’ livelihoods.
Integrating veterinary services, environmental monitoring, and human healthcare is now essential.
Why We Need a One Health Approach Now More Than Ever
1. Integrated Surveillance:
Pathogen detection should not end at the hospital. Early warning systems must include
animal reservoirs, vector monitoring, and environmental sampling.
2. Cross-disciplinary Collaboration:
Physicians, veterinarians, ecologists, microbiologists, and policymakers must work in
tandem. The silos of “medical vs. veterinary” must be broken.
3. Data Sharing and Genomic Intelligence:
Open data platforms and genomic surveillance (like INSACOG for SARS-CoV-2) should
expand to include zoonotic and vector-borne pathogens.
4. Public Health Infrastructure:
Strengthening primary care, vaccination programs, and laboratory capacity will improve
resilience against future outbreaks.
5. Community Engagement:
Farmers, pet owners, and local communities play a key role in early detection and containment of zoonoses. Culturally sensitive public awareness is vital.
Climate Adaptation and Mitigation in Health Planning
A One Health-based climate strategy must include:
Heat and Vector Early Warning Systems:
Combining meteorological and health data to forecast vector surges and plan preventive interventions.
Urban Design and Waste Management:
Preventing water stagnation, ensuring proper drainage, and managing waste to curb mosquito breeding.
Sustainable Agriculture:
Reducing pesticide and antibiotic misuse, promoting organic farming, and conserving natural predators of vectors.
Forest and Wildlife Conservation:
Protecting natural habitats reduces risky wildlife-human contact and maintains ecosystem balance.
Global Initiatives and Future Directions
Several global efforts reflect the growing importance of One Health:
Quadripartite Alliance (WHO-FAO-WOAH-UNEP):
Promotes integrated policy frameworks to tackle zoonotic threats and AMR.
Global Virome Project:
Aims to identify unknown viruses circulating in wildlife before they spill over to humans.
COP28 & Beyond:
Climate conferences are now including health discussions, signaling recognition of the climate-health nexus.
In the future, digital tools like AI-based outbreak prediction, satellite monitoring of ecosystems, and real-time genomic sequencing will become core components of One Health surveillance.
Conclusion: One Planet, One Health, One Future
The COVID-19 pandemic was a warning shot.
The next major outbreak could be triggered by deforestation in the Amazon, melting permafrost in Siberia, or flooding in South Asia.
The lines separating human, animal, and environmental health have blurred — and ignoring these linkages is no longer an option.
Adopting a One Health framework is not just scientific necessity; it’s moral responsibility.
Every clinician who diagnoses leptospirosis, every veterinarian who detects avian flu, every environmental scientist who measures water contamination — all are part of the same defense system.
As we confront the twin challenges of climate change and infectious diseases, collaboration across disciplines and borders is our best vaccine against the future.