Introduction  |  Economic benefits  |  WHO JEE – zoonotic diseases  |  OIE PVS pathway cycle  |   Resources  |   Definitions  |   Funding  |   Project planning flow chart  |   Diagnostic test tableInteractive App


Introduction to One Health


It is important to shift our way of thinking from ‘response’ e.g. how do we combat a disease that has emerged in a population to ‘causality’ e.g. what are the factors/changes that may lead to disease outbreaks. Traditionally, most infectious disease research projects have been conducted from a specific angle, usually from the human, or clinical point of view, with little emphasis put on the animal or environmental aspects of a disease. PANDORA is a consortium of African and European countries conducting global health research on emerging infectious diseases with a strong One Health focus.

Aim of this webpage

The issues surrounding One Health that should be included in a multisectoral research project are widespread and cover many different aspects of research, which is why it is difficult to plan and implement truly One Health research and why it is vital to include clinical, veterinary and environmental expertise. The aim of this web page is to provide an introduction to planning a One Health research project, including good One Health overview papers and websites, up to date definitions, a breakdown of EID and zoonotic disease information, including the most relevant clinical and veterinary diagnostic techniques, as well as a step-by-step guide to planning. This guide has a list of questions that you might need to consider when planning your project, but it is not exhaustive. It is intended to spark your research team’s thought process when it comes to ideas you will need to consider.

One Health

Clinical research and health interventions have traditionally been focussed on single diseases and are likely to have overlooked animal or environmental factors that may be important to more than one disease. For instance by killing domestic rats to reduce the burden of murine typhus/Weils disease, you are removing the food source of fleas which feed on the rats. These fleas may in turn feed on humans and increase spread of other diseases such as plague.

One Health is a collaborative initiative that aims to incorporate a multisectoral response to global and planetar health by acknowledging the roles that humans, animals and the environment play in health. This multi-angled response is vital for enabling us to see the bigger picture and identify influences that may not be apparent from a single angle. It is especially important for emerging infectious disease (EID) outbreaks, such as COVID-19, as One Health research can optimise risk mitigation and identify potential confounding factors across all sectors. Using COVID-19 as an example, the reservoir species is still unknown and there is a need to look at the farming and wildlife trade practices to help narrow down whether there are potential animal reservoirs and hosts, and which species they might be. Traditionally, ‘Animal health’ has often only referred to domesticated animals and rarely covers wildlife health, but with human settlements and agricultural practices expanding further into natural habitats, it is vital that wild animals be included too.

Human and domestic animals populations now comprise 96% of mammal biomass, with wild species of mammal accounting for only 2% of terrestrial biomass. The increasing population of humans and domestic animals has resulted in huge geographical expansion and the destruction of habitat is important. However, biodiversity and wildlife populations are in steep decline globally, so the risk of contact with wild species is likely to be reducing, but the relative opportunity rises in the peridomestic space as wildlife tries to adapt. The reduction in wild spaces that human land use creates is likely to draw wildlife species towards human settlements, and coupled with increasing wildlife farming, may provide greater opportunities for spill over events.

In a truly One Health study, it is vital not only to acknowledge the links between humans, animals and the environment when it comes to the health of all, but also that the integration of each sector into research will enable the improved health of animals, humans and the planet. This multisectoral approach will likely have a financial benefit (especially long term) over single-sector research alone. Currently, very little focus is placed on the wildlife health sector, especially within governments. Groups such as the Wildlife Disease Association (WDA) and the International Union for Conservation of Nature (IUCN) are trying to address this gap.

It is vital to identify priority EIDs and zoonotic diseases at a country and a regional level, and do this in a multidisciplinary manner, including members from clinical, public health, veterinary, agricultural and environmental departments. Whilst there is unlikely to be a wildlife health sector within government structures currently, this area should not be overlooked. Practices should be shaped and informed by local contexts, including religion and culture and acknowledge that the same animals and the environment play different roles to different people. We need to create a disciplinary community for emerging infectious disease and zoonoses One Health epidemiology. We need to have a deep knowledge of the environment, animal lifecycles and human interactions to truly understand why and how these diseases may affect us.

An understanding of these diseases is unlikely to be enough however. Identifying which organism(s) matter would require large-scale surveillance, which, for low and middle income countries (LMICs) where zoonoses often emerge, would be far too costly to cover the many species that may be implicated. Whilst effective surveillance systems would ultimately include wildlife too, most countries struggle to maintain surveillance for domestic animals. The most cost-effective approach is likely to be prevention through human actions that reduce the risk of emergence. Research into social, economic and developmental approaches that respect nature and wildlife, restore ecological systems and reduce stressful contact between humans, domestic animals and wildlife, as well as better integration in the peridomestic space so that wildlife is not so dependent on human sources of food and habitation is needed.



Economic benefits of One Health research and programmes

It is important to note that the incorporation of clinical, veterinary and environmental interventions into one control programme can reduce the overall cost for public and private health spending, despite often having a large initial cost attached to it. Whilst these initial costs, when looked at from an individual stake holders’ point of view, may appear larger than the benefits to that sector alone, when the benefits to other sectors (i.e. taking a One Health approach) are taken into account (e.g. private sector/household spending, agricultural benefits), it may be found that the benefits outweigh the initial costs. The cost of the intervention can therefore be spread between the sectors that benefit, enabling greater cost-effectiveness to each. This cost-benefit trade-off is likely to apply to domestic animal and human interventions, and there is plenty of literature in this area. It is unlikely to cover wildlife, and although wildlife does not account for a large proportion of zoonotic transmission, it is important to include it in the calculations.

Conversely, this strategy may not reduce emerging pathogens at all, and potentially increase the risk, as more domestic animals arise from improved health care and monitoring. Research into understanding how these interventions work in real situations, as well as wildlife interventions will be vital. The altering of human actions is likely to be a key factor and some research in understanding the boundaries and trade-offs will be essential.

A One Health Framework for Estimating the Economic Costs of Zoonotic Diseases on Society has been published. It covers domestic animal and human disease, as most zoonotic diseases arise from domestic animals, although lacks coverage of wildlife and the environment. It is the emerging infectious diseases that will be the challenge to estimate:



WHO Joint External Evaluations – zoonotic diseases

From WHO website: Joint external evaluations (JEE) are voluntary, collaborative, multisectoral process to assess country capacities to prevent, detect and rapidly respond to public health risks whether occurring naturally or due to deliberate or accidental events. The JEE helps countries identify the most critical gaps within their human and animal health systems in order to prioritize opportunities for enhanced preparedness and response.

The JEEs, although not covering wildlife or the environment, acknowledge that a One Health approach needs to be taken to adequately respond to the majority of public health issues from a clinical perspective. One section of the JEE report is zoonotic diseases, in which the following priorities are scored:

  • Whether a country has created a priority list of 5 zoonotic diseases (which has been approved by a multidisciplinary team)
  • Is there a formal multisectoral policy for collaboration on zoonotic diseases in the country?
  • Is there a mechanism for joint risk assessment for zoonotic disease events?
  • Are there surveillance systems in place for zoonotic diseases?
  • Does the country have capacity to respond to more than 80% of zoonotic events on time? What is the timeliness at present?
  • Does the country have a preparedness plan for handling emerging or re-emerging zoonotic diseases with verification?

Note that even in the JEEs, the word ‘zoonotic’ seems to be used to describe both ‘true’ zoonoses and emerging infectious diseases.



World Organisation for Animal Health PVS pathway cycle

The World Organisation for Animal Health (OIE) has also created a similar programme to the WHO’s JEEs, which targets 45 critical competencies in veterinary services, which covers mainly domestic animals. It was launched in 2007 and there are currently 140 countries engaged in the pathway.



List of resources

These links to websites and research papers provide an overview of One Health from reliable, up to date sources, such as the WHO and One Health global network. If you are not familiar with One Health, these provide good summary information of the concepts.

Organisation website links

WHO One Health pages:

One Health Global network:


One Health commission:

One Health Initiative:

World Organisation for Animal Health:

FutureLearn One Health online course:

A framework for One Health research -

We have also provided a forum section on the PANDORA-ID-NET hub, where you can ask our experts, and other hub users, for advice and guidance on preparing a One Health research programme.

We have also provided a list of useful One Health publications. Click here to go to the One Health publication resources page.




One Health is an evolving concept and as such, definitions and concepts are also developing. Below are some general definitions that apply to One Health.

One Health – (from Stone Mountain) the inter-sectoral collaborative approach necessary to prevent, detect and control emerging, and re-emerging infectious diseases that exist at the animal-human ecosystems interface.

One Health is a comprehensive approach to health that focuses on:

A. Improving health and well-being through the prevention of risks and the mitigation of effects of crises (e.g. emerging diseases) that originate at the interface between humans, animals and their various environments.

B. Promoting multi (cross) sectoral collaborations and a “whole of society” treatment of health hazards, as a systemic change of perspective in the management of risk.

(Stone Mountain Process on One Health - Governance and Global Network October 31 – November 1, 2011 Emory University, Atlanta, GA, USA)

Zoonosis/zoonotic disease – (from WHO, 1959) an infection that is naturally transmissible from animals to humans with an animal reservoir.

Zooanthroponosis or reverse zoonosis – infection naturally transmissible from humans to animals with a human reservoir.

Emerging infectious disease – (from WHO) “A new disease that is affecting a population for the first time, or an existing disease that is rapidly spreading geographically or affecting an increasing number of people.”

Re-emerging infectious disease – (taken from John Hopkins Medicine) “Re-emerging diseases are diseases that reappear after they have been on a significant decline. Re-emergence may happen because of a breakdown in public health measures for diseases that were once under control. They can also happen when new strains of known disease-causing organisms appear.”

(Pathogen) spill over event/infection – (Power and Mitchell Spill over infection, also known as pathogen spill over and spill over event, occurs when a reservoir population with a high pathogen prevalence comes into contact with a novel host population. The pathogen is transmitted from the reservoir population and may or may not be transmitted within the host population.

Secondary epidemiological cycle - when the original reservoir host is no longer involved e.g. human-tsetse-human cycle (also when a disease jumps from a wild animal to a domestic animal cycle). These secondary hosts are called maintenance hosts.

One Health research - acknowledges the links between humans, animals and the environment when it comes to the health of all. Planning a study which includes multisectoral expertise improves the health of animals, humans and the planet and will likely have a financial benefit.



Funding sources for One Health projects

Many funding organisations have One Health grants available throughout the year. These are often advertised on Twitter.

The One Health Research Foundation -



Project planning flow chart

This section of the One Health hub is designed to assist you in the process of designing a One Health project. As One Health is by nature, you will need to involve colleagues from different sectors, such as veterinary, agriculture, environmental etc. in the design and planning of your study. We have broken down the project planning into the following 5 sections:

Step 1: Identify disease(s) and research question

You are likely to already have a disease or specific research question in mind. You may find that focussing on one disease may mean you miss benefits or impacts on others, especially if looking at interventions. For example, you may find that changing WASH practices may reduce a number of diseases. Remember that a One Health project should:

  • Identify the linkages between humans, animals and the environment
  • Benefit all sectors (e.g. humans, animals and the environment) and/or show that there is a financial advantage when working in a multisectoral way

Step 2: Consider the One Health questions to be asked

Does your chosen disease/project have a One Health element? Below are a list of questions you should consider when planning your research. All of these factors need to be taken into consideration based on how they apply to the country or countries you are planning to undertake your research in. This list is not exhaustive, it should help to trigger a wider thought process when approaching your project. It will also be vital to discuss these kinds of questions with your colleagues from other sectors.

Environmental factors

  • What types of natural environment are there? E.g. forest, desert etc.
  • What types of built environment are there? E.g. rural village, industrial etc.
  • Have human settlements/farming recently encroached into wild environments such as forests?
  • What crops are being planted in this area?
  • Is it a monoculture, or are there smaller, more diverse farms?


  • Are there domesticated animals? E.g. cows, goats, dogs, chickens etc.
  • What are the lifecycles of these domesticated animals?
  • Are there wild animals? E.g. antelope, bats etc.
  • What are the lifecycles of these wild animals?
  • What kinds of veterinary services and treatments are available for domestic and wild animals in the area? E.g. are there veterinary practices/healthcare professionals available or do most people self-treat/use traditional medicines?
  • Do wild and domestic animals interact in any way? E.g. do cattle and antelope graze on the same pastures?

Human factors

  • What social or behavioural factors might play a role? E.g. cultural beliefs, customs
  • How to humans interact with the research area? (e.g. are people washing clothes in water sources, do children play in the forest?
  • Is there access to a clean source of water such as a pump, or do people use natural water sources such as lakes and rivers?
  • How many people live within one house/commune? This might influence spread of a disease
  • What risk factors exist in these communities? E.g. nutritional status such as vitamin D deficiencies, common comorbidities
  • What are the population dynamics like? E.g. is this a small village or a large town? Is there a high rate of immigration/emigration from the area?
  • What are common occupations in the area? E.g. farming, pastoralists, hunters, shop keepers
  • How is food generally prepared? (many zoonoses are transmitted indirectly through food)
  • If you ask people to change their behaviour, what alternative options are available? How might these alternatives affect the situation?

Human/animal interactions

  • How many domestic animals does each family typically own?
  • How many species does each family typically own?
  • How are animals kept? E.g. do they live in the same building as humans?
  • Do people eat bush meat?
  • What types of bush meat is available?
  • How often do people attend markets?

Disease vectors and animal hosts

  • Are there known disease vectors associated with this/these disease(s)? E.g. mosquitoes, fleas
  • Are there known animal (intermediate) hosts associated with this/these disease(s)? E.g. rats, bats
  • Has recent environmental changes affected the range of these vectors/hosts? E.g. increase in human settlements may increase standing water, where mosquitoes can breed
  • Are the lifecycles of these vectors/hosts known?
  • Do these lifecycles differ to similar vectors/hosts in other countries/continents? E.g. bats in south East Asia are known to inhabit caves and often come into contact with humans, whereas bats in Africa generally live in trees and have little contact with humans
  • Are there control programmes already in place for these vectors/hosts? E.g. insecticide treated bed nets

Step 3: Identify the sectors you should be working with (e.g. veterinarians, agriculturalists etc.)

These can be both local and international resources (e.g. the local veterinarian and/or PANDORA consortium veterinarian experts)

Step 4: Use the table to identify which tests to use

The below table of EID and zoonotic diseases is designed to help you identify potential diagnostic tools for your study. There may be one diagnostic test available for all species, or you may find that there are multiple ones of varying sensitivity and specificity. Whilst we have tried to include as many as possible, this is an evolving area and as such, there may be new tests and concepts that are not yet included. Surveillance and diagnostic testing may differ depending on the species involved.


Diagnostic test table

Click on the disease you are interested in to see the full information regarding human, animal and disease vector diagnostics


Step 5: Check the relevant ethical issues

It is important that the ethical considerations of a One Health be considered. As you/your group/collaborators are likely to be from one or two specific disciplines, whilst One Health necessarily spans many, you many need to acclimatise yourself with the ethical concerns of other areas (e.g. if you are a microbiologist, you will likely need to research/find people with expertise in veterinary and/or environmental ethics.

Ethics are likely to be institution and country specific, especially for the country/countries you are conducting the research in. Below is a list of general research guidelines for clinical, veterinary and environmental research to provide an overview and concepts to consider.

We also have a separate ethics page which you may find useful:

Paper – Does One Health require a novel ethical framework? -

Veterinary research ethical guidelines/framework

OIE – Guidelines for responsible conduct in veterinary research -

Clinical research ethical guidelines/framework

WHO – Ethical standards and procedures for research with human beings -

Environmental research ethical guidelines/framework

FAO – Ethical issues in food and agriculture -

Plants ethical guidelines/framework

Paper on agricultural ethics -


The content on these pages was developed by Dr Najmul Haider (RVC), Professor Richard Kock (RVC) and Dr Linzy Elton (UCL)