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Zoonoses are diseases caused by pathogens (bacteria, viruses, parasites, or fungi) that can spread between humans and animals. In the last three decades, 75% of new diseases in humans have originated in animals. These include all recent pandemics such as the H1N1 (‘swine’) Influenza, and COVID-19 (caused by SARS-CoV-2). Zoonoses are said to be ‘emerging’ when they have recently spilled over into humans or have expanded into to new geographic regions. Emerging diseases represent a global health risk because there is no natural immunity for these diseases among people. 

Experts highlight the need for a ‘One Health’ approach to prevent the emergence of zoonotic diseases. One Health is defined by the UK Government as referring to two related ideas: 1) the concept that the health of humans, animals, plants, and the environment we live in are inextricably linked and interdependent and 2) the collaborative and sustained effort of multiple disciplines working locally, nationally, regionally, and globally to attain optimal health for all living things.  

During the G7 and the G20 summits, world leaders agreed to implement One Health approaches in future pandemic prevention and preparedness policies. 


Key points  

  • The number of emerging zoonoses is increasing as there are more frequent interactions between humans and domestic or wild animals. This is driven by increases in animal farming and encroachment into natural habitats due to climate change, land clearance for agriculture and expanding urban developments.  
  • Preventing zoonotic disease emergence before widespread human-to-human transmission is cheaper and has better public health outcomes. Strategies for prevention include reducing risky human-animal interactions, improving the welfare of domestic and wild animals, and refining global surveillance systems for people and animals. 
  • The UK carries out a risk-based, early warning, surveillance approach for animal and human health. It is involved in several international surveillance networks including OFFLU, which monitors animal influenzas that can infect people.  
  • Developing adaptable responses and scalable capacity in public health systems; expanding capabilities to identify and investigate unknown pathogens that are yet to emerge (the principle of ‘Disease X’); and quickly responding to emerging threats when they are detected have been identified by the Coronavirus: Lessons learnt and Biosecurity and national security inquiries as priority actions for the UK. 
  • The Public Administration and Constitutional Affairs Committee recommended the establishment of an independent public inquiry into the UK Governments’ response to the COVID-19 pandemic. 



POSTnotes are based on literature reviews and interviews with a range of stakeholders and are externally peer-reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including: 

Members of the POST Board* 

Dr Opi Outhwaite, St Mary’s University Twickenham * 

Exotic Disease Policy, Defra* 

British Veterinary Association* 

British Hen and Welfare Trust * 

Dr Graham Smith and Dr Sharon Brookes, Animal and Plant Health Agency* 

Catherine McLaughlin and Dr Claire White*, National Farmers’ Union  

Professor Tom Solomon, National Institute for Health Research, Health Protection Research Unit in Emerging and Zoonotic Infections* 

Professor Eric Fèvre, University of Liverpool; International Livestock Research Institute* 

Biotechnology and Biological Sciences Research Council* 

Wildfowl and Wetlands Trust* 

Professor David Heymann, London School of Hygiene and Tropical Medicine* 

Professor Graham Medley and Dr Adam Kucharski, London School of Hygiene and Tropical Medicine 

Professor Bryan Charleston, The Pirbright Institute*  

Professor Andrew Cunningham, Zoological Society of London* 

Dr Julian Drewe*, Professor Nicola Lewis, Professor Joanne Webster*, Professor Oliver Pybus, Professor Javier Guitian, Royal Veterinary College 

Professor Alan Radford, University of Liverpool 

Dr Cathy Roth and Dr Nicola Wardrop, Foreign, Commonwealth and Development Office* 

Rachel Cooper, Helen Tomkys and Emma Stapley, Department of Health and Social Care* 

Dr Emily Dobell, Dr Hilary Kirkbride, Dr Cat McGillycuddy, Tina Endericks, Zoe Gibney, UK Health Security Agency* 

Dr Charis Enns and Team, Wildlife Trade Futures* 

Dr Osman Dar, Chatham House  

Professor Christl Donnelly, University of Oxford; Imperial College London 

Dr Bethan Purse, UK Centre for Ecology and Hydrology 

Joint Committee on Vaccine and Immunisation Secretariat 

Professor Kate Jones, University College London   


* denotes people and organisations who acted as external reviewers of the briefing. 

Further readings

  • PN 597: Climate Change and Vector-Borne Diseases in Humans in the UK 
  • PN 392: Livestock Diseases  

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