PREVENTING THE NEXT PANDEMIC
Zoonotic diseases and how tobreak the chain of transmission

A Scientific Assessment with Key Messages for Policy-Makers
A Special Volume of UNEP’s Frontiers Report Series© 2020 United Nations Environment ProgrammeISBN No: 978-92-807-3792-9
Job No: DEW/2290/NA
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Pandemic: Zoonotic diseases and how to break the chain of transmission. Nairobi, Kenya.
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PREVENTING THE NEXT PANDEMIC
Zoonotic diseases and how tobreak the chain of transmission

A Scientific Assessment with Key Messages for Policy-Makers
A Special Volume of UNEP’s Frontiers Report Series

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Acknowledgements
The United Nations Environment Programme (UNEP)
would like to thank the authors, reviewers and the
supporting organizations for their contribution to the
preparation of this rapid scientific assessment report.
Lead Author
Delia Grace Randolph (Natural Resources Institute, NRI, ofthe University of Greenwich, and International LivestockResearch Institute, ILRI, Nairobi, Kenya).
Co-Authors
Johannes Refisch (UNEP, Nairobi, Kenya), Susan MacMillan(International Livestock Research Institute, ILRI, Nairobi,
Kenya), Caradee Yael Wright (South African Medical
Research Council, SAMRC, Pretoria, South Africa), Bernard
Bett (International Livestock Research Institute, ILRI,
Nairobi, Kenya), Doreen Robinson (UNEP, Nairobi, Kenya),
Bianca Wernecke (South African Medical ResearchCouncil, SAMRC, Pretoria, South Africa), Hu Suk Lee(International Livestock Research Institute, ILRI, Nairobi,
Kenya), William B. Karesh (EcoHealth Alliance, New York,USA), Catherine Machalaba (EcoHealth Alliance, New York,USA), Amy Fraenkel (Secretariat of the Convention on
the Conservation of Migratory Species of Wild Animals,
CMS, Bonn, Germany), Marco Barbieri (Secretariat of theConvention on the Conservation of Migratory Species ofWild Animals, CMS, Bonn, Germany) and Maarten Kappelle(UNEP, Nairobi, Kenya).
UNEP Frontiers series editors
Maarten Kappelle and Pinya Sarasas (both: UNEP, Nairobi,
Kenya).
Reviewers
Hilary Allison (World Conservation Monitoring Centre,
UNEP-WCMC, Cambridge, UK), Neville Ash (World
Conservation Monitoring Centre, UNEP-WCMC,
Cambridge, UK), Daniel Bergin (GlobeScan, Hong
Kong SAR, People’s Republic of China), Tianna Brand(World Organisation for Animal Health, OIE, Paris,
France), Alessandro Broglia (Italian Office, Vétérinaires
Sans Frontières, VSF, Legnaro, Italy), Randy Burd (LongIsland University, Brookville, NY, USA), Neil D. Burgess(World Conservation Monitoring Centre, UNEP-WCMC,
Cambridge, UK), H. David Cooper (Secretariat of theConvention on Biological Diversity, CBD, Montreal,
Canada), Miguel Cardo (Portuguese Office, Vétérinaires
Sans Frontières, VSF, Lisbon, Portugal), Keti Chachibaia

Acknowledgements(United Nations Development Programme, UNDP, New
York, NY, USA), Katie Clow (Canadian Office, Vétérinaires
Sans Frontières (VWB/VSF), Ottawa, Ontario, Canada),
Patricia Cremona (International Union for Conservationof Nature, IUCN, Gland, Switzerland), Sergey Dereliev(Secretariat of the Agreement on the Conservation of
African-Eurasian Migratory Waterbirds, AEWA, Bonn,
Germany), Logan Ende (UNEP, Washington DC, USA), Lisa
Farroway (United Nations Development Programme,
UNDP, New York, NY, USA), Francesco Gaetani (Latin
American and Caribbean Regional Office, UNEP, Panama
City, Panama), Susan Gardner (UNEP, Nairobi, Kenya),
Suren Gazaryan (Secretariat of the Agreement on theConservation of Populations of European Bats, EUROBATS,
Bonn, Germany), Thomas R. Gillespie (Emory University,
Atlanta, GA, USA), Margherita Gomarasca (Vétérinaires
Sans Frontières, VSF, Brussels, Belgium), Danny Govender(South African National Parks, SANParks, Pretoria, South
Africa), Jason Jabbour (North American Regional Office,
UNEP, Washington, DC, USA), Luc Janssens de Bisthoven(Royal Belgian Institute of Natural Sciences, Brussels,
Belgium), Margaret Kinnaird (World Wide Fund For
Nature – International, WWF-INT, Gland, Switzerland),Richard Kock (Royal Veterinary College, RVC, Universityof London, London, UK), Fabian Leendertz (Robert Koch
Institute, Berlin, Germany), Jian Liu (UNEP, Nairobi, Kenya),
Brian Lutz (United Nations Development Programme,
UNDP, New York, NY, USA), Riks Maas (Wageningen
Bioveterinary Research, Wageningen University andResearch Center, WUR, Lelystad, Netherlands), Kelly
Malsch (World Conservation Monitoring Centre, UNEPWCMC, Cambridge, UK), Stefano Mason (Agronomes etVétérinaires sans Frontières, AVSF, Nogent-sur-Marne,
France), Paige McClanahan (UNEP, Nairobi, Kenya),
Wander Meijer (GlobeScan, Hong Kong SAR, People’s
Republic of China), Stefano Messori (World Organisation
for Animal Health, OIE, Paris, France), E.J. Milner-Gulland(Interdisciplinary Centre for Conservation Science andOxford Martin Programme on Illegal Wildlife Trade,
University of Oxford, and GCRF TRADE hub, Oxford, UK),
Marco de Nardi (Safe Food Solutions, SAFOSO, Köniz,Switzerland), Maryam Niamir-Fuller (Formerly UNEP –Global Environment Facility, UNEP-GEF, Virginia, USA),
Scott Newman (Food and Agriculture Organization,
FAO, Rome, Italy), James O’Rourke (Chadron State
College, Chadron, NE, USA), Midori Paxton (United
Nations Development Programme, UNDP, New York, NY,
USA), Kathryn Phillips (World Conservation Monitoring
Centre, UNEP-WCMC, Cambridge, UK), Gert Polet (World
Wide Fund For Nature – Netherlands, WWF-NL, Zeist,
Netherlands), Kristina Rodina (Food and Agriculture
Organization, FAO, Rome, Italy), Cristina Romanelli (Worldi

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Health Organisation, WHO, Geneva, Switzerland), Pinya
Sarasas (UNEP, Nairobi, Kenya), Tim Scott (United Nations
Development Programme, UNDP, New York, NY, USA),
Alexander Shestakov (Secretariat of the Convention on
Biological Diversity, CBD, Montreal, Canada), Roy Small(United Nations Development Programme, UNDP, New
York, NY, USA), Emily Tagliaro (World Organisation for
Animal Health, OIE, Paris, France), Edouard Timmermans(Vétérinaires Sans Frontières, VSF, Brussels, Belgium),
Gregorio Torres (World Organisation for Animal Health,OIE, Paris, France), Gregorio Velasco Gil (Food andAgriculture Organization, FAO, Rome, Italy), Kaavya
Varma (United Nations Development Programme, UNDP,
New York, NY, USA), Yolanda Vaz (Portuguese Office,
Vétérinaires Sans Frontières, VSF, Lisbon, Portugal), Ana
Vukoje (Asia-Pacific Regional Office, UNEP, Bangkok,
Thailand), Chris Walzer (Wildlife Conservation Society(WCS), New York, NY, USA), Christopher Whaley (Scientificand Technical Advisory Panel of the Global Environment
Facility, GEF-STAP, Washington, DC, USA), Derek Wu(GlobeScan, Hong Kong SAR, People’s Republic of China),
Michelle Wyman (National Council for Science and theEnvironment, NCSE, Washington, DC, USA), Makiko Yashiro(Asia-Pacific Regional Office, UNEP, Bangkok, Thailand),
Edoardo Zandri (UNEP, Nairobi, Kenya), Jinhua Zhang(Asia-Pacific Regional Office, UNEP, Bangkok, Thailand) and
Max Zieren (Asia-Pacific Regional Office, UNEP, Bangkok,
Thailand).

Thanks also to:
Jimmy Smith (ILRI); Judith Akoth, Inger Andersen, Magda
Biesiada, Alexander Caldas, Harsha Dave, Angeline
Djampou, Sandor Frigyik, Tito Kimathi, Emily Kilonzi,
Rachel Kosse, Fred Lerionka, Jian Liu, Lu Liu, Janet
Macharia, Isabel Martínez, Nada Matta, Joyce Mavoungou,
Abdelmenam Mohamed, Joyce Msuya, Pascil Muchesia,
Jane Muriithi, Daniel Nthiwa, David Osborn, Rafael Peralta,
Julia Rugo, Nandita Surendran, Ying Wang, Edoardo Zandri
and Jing Zheng (all: UNEP, Nairobi, Kenya); and David
Berman (independent).
Partners
The United Nations Environment Programme would liketo express its gratitude to the International LivestockResearch Institute (ILRI, Nairobi, Kenya), the South African
Medical Research Council (SAMRC, Pretoria, South
Africa) and the Secretariat of the Convention on theConservation of Migratory Species of Wild Animals (CMS,
Bonn, Germany) for their extraordinary support to thedevelopment, launch and communication of this rapid
scientific assessment report.

Secretariat and project coordination
Maarten Kappelle, Pinya Sarasas, Sofía Méndez Mora andAllan Lelei (all: UNEP, Nairobi, Kenya).
Language editing
Susan MacMillan (International Livestock ResearchInstitute, ILRI, Kenya), Maarten Kappelle, Paige
McClanahan and Pinya Sarasas (all: UNEP, Nairobi, Kenya).
Graphics, design and layout
Audrey Ringler, UNEP, Nairobi, Kenya.
Communications, media and outreach
Daniel Cooney, Atif Ikram Butt, Salome Mbeyu Chamanje,
David Cole, Nicolien De Lange, Florian Fussstetter, Maria
Galassi, Nancy Groves, Paige McClanahan, Neda Monshat,
Pooja Munshi, Moses Osani, Andrew Raven, Lisa Rolls,
Keishamaza Rukikaire, Sajni Shah, Rajinder Sian, Neha Sud
and Richard Waiguchu (all: UNEP, Kenya); David Aronson,
Annabel Slater and Michael Victor (all: ILRI, Kenya); andMatthew Davis and Michelle Geis Wallace (both: BURNESS,
Bethesda, MD, USA).

ii

Acknowledgements

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

UNEP and ILRI are thankful for the support received from the following organisations:Acknowledgementsiii

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmissioniv

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Contents
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iContents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Abbreviations and Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Forewords. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Key Messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
SECTION I:
		Overview of emerging infectious diseases including zoonoses .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 11
What are emerging diseases and what are zoonoses? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
When do zoonoses become human disease outbreaks?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Seven major anthropogenic drivers of zoonotic disease emergence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Other factors playing a role in zoonotic disease emergence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

SECTION II:

Coronaviruses in a One Health context .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 21
What are coronaviruses? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Common elements and origins of coronavirus pandemics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

SECTION III:		

Understanding the linkages between habitat loss, the trade and use of wildlife, andthe emergence of novel zoonoses .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 29
Habitat and biodiversity loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
The roles of wildlife harvesting, farming and trade in pathogenic spread. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Zoonotic risks of wildlife use, trade and consumption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

SECTION IV:

Managing and preventing zoonoses: How One Health can help .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 39
The One Health approach to controlling zoonoses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Track record in managing zoonoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Lessons from managing previous coronavirus outbreaks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

SECTION V:

Preventing future zoonotic pandemics: What more could be done?.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 45
One Health aspects of zoonoses control and prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Addressing the anthropogenic drivers of zoonoses emergence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Strengthening the environment dimensions of the One Health approach. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Leveraging innovations and new technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Responding to public and policy demand for the prevention and control of zoonoses. . . . . . . . . . . . . . . . . 48
Transforming and re-governing food systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Sustainable use of wild resources and Multilateral Environmental Agreements. . . . . . . . . . . . . . . . . . . . . . . . 50
Interventions at the human-livestock interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Towards evidence-informed policy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Ten key policy recommendations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Graphic References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Contents

1

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

2

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Abbreviations and Acronyms
AIDS

acquired immune deficiency syndrome

BSE

bovine spongiform encephalopathy

CBD

Convention on Biological Diversity

CGIAR

A global partnership for a food secure future

CITES

Convention on International Trade in Endangered Species of Wild Fauna and Flora

CMS

Convention on Migratory Species (Bonn Convention)

COP

Conference of the Parties

COVID-19

coronavirus disease 2019DNA

deoxyribonucleic acidEID

emerging infectious disease

FAO

Food and Agriculture Organization of the United Nations

GDPgross domestic product

HCoV-OC43

human coronavirus subtype OC43

HIV/AIDS

human immunodeficiency virus/acquired immune deficiency syndrome

HPAI

highly pathogenic avian influenza

IBD

inflammatory bowel disease

ILRI

International Livestock Research Institute

MERS

Middle East respiratory syndrome

MERS-CoV

Middle East respiratory syndrome coronavirus

OIEWorld Organisation for Animal HealthPED

porcine epidemic diarrhoea

RNAribonucleic acid

RVF

Rift Valley fever

SARS

severe acute respiratory syndrome

SARS-CoV

severe acute respiratory syndrome coronavirus

SARS-CoV-2

severe acute respiratory syndrome coronavirus 2

SIVsimian immunodeficiency virus

TGEtransmissible gastroenteritis

UNEP

United Nations Environment Programme

UNESCO

United Nations Educational, Scientific and Cultural Organization

UNICEF

United Nations Children’s Fund

WHO

World Health Organization

Abbreviations and Acronyms

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Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Foreword by the Executive Director of UNEPCOVID-19 has caused profound damage to humanhealth, societies and economies in every corner of theworld. This illness is zoonotic, a type of disease thattransmits between animals and humans. It may be theworst, but it is not the first. We already know that 60 per
cent of known infectious diseases in humans and 75 percent of all emerging infectious diseases are zoonotic.
Ebola, SARS, the Zika virus and bird flu all came to people
by way of animals.
As we seek to build back better after COVID-19, we needto fully understand the transmission of zoonoses, thethreats they pose to human health and how to minimize
the risk of further devastating outbreaks. This requires anambitious line of enquiry, in which this report, Preventing
the next pandemic: Zoonotic diseases and how to breakthe chain of transmission, is a crucial first step.
The report—produced in partnership with universities,
research institutions, UN agencies and the secretariats
of several multilateral environmental agreements—
identifies key anthropogenic drivers for the emergence of
zoonoses, from agricultural intensification and increased
demand for animal protein to the conversion of landand climate change. These drivers are destroying natural
habitats and seeing humanity exploiting more species,
which brings people into closer contact with disease
vectors. Once established in humans, these diseases
quickly spread across our interconnected world, as wehave seen with COVID-19.
Understanding these drivers is essential to inform
effective strategies and policy responses toprevent future outbreaks. This report makes many
recommendations, all based on the One Health approach,which unites experts from multiple disciplines—publichealth, animal health, plant health and the environment—to deliver outcomes that improve the health of people,
wildlife and the planet.
The recommendations include expanding scientificenquiry into zoonoses, regulating and monitoring
traditional food markets, incentivizing the legal wildlife
trade and animal husbandry to adopt zoonotic control
measures, and radically transforming food systems.
Above all, governments, citizens and the private sector
need to work together. This is a global challenge that
nobody can hide from. It crosses every discipline andevery border. The drivers of pandemics are often also
the drivers of climate change and biodiversity loss—twolong-term challenges that have not gone away during
the pandemic.

4

At the heart of our response to zoonoses and the otherchallenges humanity faces should be the simple ideathat the health of humanity depends on the health ofthe planet and the health of other species. If humanity
gives nature a chance to breathe, it will be our greatest
ally as we seek to build a fairer, greener and safer world
for everyone.

Inger Andersen
Executive Director
United Nations Environment Programme
July 2020

Foreword

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Foreword by the Director General of ILRI
I am honoured to introduce this collaborative report byscientists of the United Nations Environment Programme(UNEP), the International Livestock Research Institute(ILRI) and the South African Medical Research Council
in partnership with other UN and multilateral agencies
and leading universities and research institutions. It isaltogether fitting that environment, livestock and medical
expertise should join up to help understand and stem therise of human contagions.
This report will deepen the reader’s understanding of
the virus causing the global COVID-19 pandemic andother pathogens that have similarly jumped species fromtheir animal to human hosts. These ‘zoonotic’ diseases
are increasing as the world’s growing human population
broadens and deepens interactions among people,
animals and environments.
To date, most efforts to control zoonotic diseases havebeen reactive rather than proactive. COVID-19 has madeus all aware that it’s time to change that. To prevent future
outbreaks of novel zoonotic diseases, we need to address
the root causes of their emergence. We need among otherthings to break down disciplinary and organisational silos,
to invest in public health programmes, to farm sustainably,
to end the over-exploitation of wildlife, to restore land andecosystem health and to reduce climate change.
The only way to achieve all of this is to boost collaboration
among agencies that work on environment, animal andhuman health. In the past two decades, ‘One Health’—aholistic, inter-sectoral and interdisciplinary approachthat focuses on where the health of people, animals
and environments converge—has emerged as themost promising way to prevent and manage zoonotic
diseases. I have long championed use of ‘One Health’, butwhile experts agree that it is the optimal way to ensurea healthier future for all of us, this approach needs to bestrengthened and mainstreamed everywhere, particularly
the environment aspects of One Health, and it needs toreceive vastly greater financial and institutional support.
We must work in productive and novel ways across thehuman, animal and environment sectors and at every
level—from village to ministry to global. This collaborative
work by leading environment, livestock and humanhealth organisations is an example of such vital crosssector work.

these new coalitions will enable us to ‘build back’ healthy
ecosystems while also meeting the world’s Sustainable
Development Goals, with historic and enduring returns
on investment. This report is an early attempt to outline
ways by which institutions of all kinds—in government,
business and civil society—might work together to createsuch a legacy.

Jimmy Smith
Director General
International Livestock Research Institute
July 2020

United and proactive in moving a healthy peopleanimal-environment development agenda forward,
governments, agencies and communities together canstop future zoonoses from happening. At the same time,

Foreword

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Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

6

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Key messages
This evidence-based scientific assessment has identified
the following ten key messages for decision-makers:
1.

DE-RISKING FOOD SYSTEMS: Many new sciencebased policy reports continue to focus on the global
public health emergency caused by the COVID-19
pandemic, following the fast spread of the infectious
SARS-CoV-2 virus of zoonotic origin. We need moreevidence-based scientific assessments, such as thisone, to examine the environmental and zoonotic
context of the current pandemic, as well as the risk of
future zoonotic disease outbreaks.

2.

URGENCY: Diseases are emerging more frequently
from animals. Rapid action is necessary to fill thescience gap and fast-track the development ofknowledge and tools to help national governments,
businesses, the health sector, local communities andother stakeholders—especially those with limited
resources—to reduce the risk of future pandemics.

3.

REPORT AUDIENCE: To help fill this gap, a scientificassessment was conducted to explore the role ofwild and domesticated animals in emerging zoonotic
infectious diseases. This rapid assessment is designed
for decision-makers in government, business and civilsociety at all levels and in all regions.

4.

SCOPE OF THE PROBLEM: About 60 per cent of
human infections are estimated to have an animal
origin. Of all new and emerging human infectious
diseases, some 75 per cent “jump species” fromother animals to people. Most described zoonoses
happen indirectly, e.g. via the food system.

5.

OUTBREAK FREQUENCY AND PREDICTABILITY:
The frequency of pathogenic microorganisms jumping
from other animals to people is increasing due tounsustainable human activities. Pandemics such as the
COVID-19 outbreak are a predictable and predicted
outcome of how people source and grow food, tradeand consume animals, and alter environments.

6.

CONNECTIVITY AND COMPLEXITY: The links
among the wider environment, biodiversity andemerging infectious diseases are complex. Whilewildlife is the most common source of emerging
human disease, domesticated animals may beoriginal sources, transmission pathways, or amplifiersof zoonotic disease. Such linkages—as well as theinterconnectedness with issues such as air and water
quality, food security and nutrition, and mental andphysical health—should inform policies that address
the challenges posed by current and future emerging
infectious diseases, including zoonoses.

Key Messages

7.

DISEASE DRIVERS: Seven human-mediated factors
are most likely driving the emergence of zoonotic
diseases: 1) increasing human demand for animal
protein; 2) unsustainable agricultural intensification;3) increased use and exploitation of wildlife; 4)
unsustainable utilization of natural resources
accelerated by urbanization, land use change
and extractive industries; 5) increased travel andtransportation; 6) changes in food supply; and 7)
climate change.

8.

IMPACT AND COST: Emerging zoonotic diseases
threaten human and animal health, economic
development and the environment. The greatest
burden of zoonotic disease is borne by poor people,
but emerging infectious diseases impact everyone,with monetary losses of emerging infectious diseasemuch greater in high-income countries. Given thata single zoonotic outbreak can incur trillions of
US dollars in costs across the globe, prevention issignificantly more cost-effective than response.

9.

POLICY OPTIONS: This assessment recommends
ten policy response options to reduce the risk of
future zoonotic pandemics and to ‘build back better’:(i) raise awareness of health and environment risks
and prevention; (ii) improve health governance,
including by engaging environmental stakeholders;(iii) expand scientific inquiry into the environmental
dimensions of zoonotic diseases; (iv) ensure fullcost financial accounting of the societal impacts
of disease; (v) enhance monitoring and regulationof food systems using risk-based approaches; (vi)phase out unsustainable agricultural practices;(vii) develop and implement stronger biosecurity
measures; (viii) strengthen animal health (including
wildlife health services); (ix) build capacity among
health stakeholders to incorporate environmental
dimensions of health; and (x) mainstream andimplement One Health approaches. These policy
options are discussed in detail in Section Five of thisreport.

10. ONE HEALTH: This report confirms and builds on the
conclusions of the FAO-OIE-WHO Tripartite Allianceand many other expert groups that a One Healthapproach is the optimal method for preventing aswell as responding to zoonotic disease outbreaks
and pandemics. Adopting a One Health approach,which unites medical, veterinary and environmental
expertise, will help governments, businesses and civilsociety achieve enduring health for people, animals
and environments alike.

7

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

8

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Introduction
As the UN Framework for the Immediate Socio-economic
Response to COVID-19, published in April 2020, says:“The success of post-pandemic recovery will also be
determined by a better understanding of the context
and nature of risk.1 In view of the COVID-19 crisis, thisincludes developing and maintaining a global mappingof encroachment, illegal trade, wet markets, etc. thatare pathways for future pathogen transmission
and thus potential future zoonoses identified. It will
also mean supporting efforts to arrest ecosystem
encroachments and harmful practices, restore degradedecosystems, close down illegal trade and illegal wet
markets, while protecting communities that dependon these for their food supply and livelihoods. This
will be delivered in part by adhering to existingguidance by the Convention on International Trade inEndangered Species of Wild Fauna and Flora (CITES) andthe Convention on Migratory Species (CMS), as well as
by delivering an ambitious agreement at the Fifteenth
Conference of the Parties (COP15) of the Convention on
Biological Diversity (CBD).”
By mid-2020 though, while the world grapples with the
COVID-19 pandemic, most new papers and guidelines
focus on the public health responses to the novel SARSCoV-2 virus and the pandemic it caused. These articles
and reports emphasize the prevention and treatmentof this contagious disease, or discuss ways to safeguard
livelihoods, secure nutrition and re-build national orregional economies that are facing recessions. However,there are almost no scientific assessments that evaluate theissues that may hamper our global efforts to reduce the risk
of future zoonotic pandemics in a post-COVID-19 world.
In the spirit of the above-mentioned UN Framework for
the Immediate Socio-economic Response to COVID-19,
the United Nations Environment Programme (UNEP)—the
leading global environmental authority and advocate—has teamed up with the renowned International LivestockResearch Institute (ILRI) and other key partners to develop
an evidence-based assessment report on the risk of future
zoonotic outbreaks.
This report is one of the first that specifically focuses on theenvironmental side of the zoonotic dimension of disease
outbreaks during the COVID-19 pandemic. It tries to fill a
critical knowledge gap and provide policymakers with abetter understanding of the context and nature of potential
future zoonotic disease outbreaks. It examines the root
causes of the COVID-19 pandemic and other “zoonoses,”
which the World Health Organization defines as humanIntroductiondiseases or infections that are naturally transmissible fromvertebrate animals to humans. The report also looks atwhere zoonoses come from and how we can reduce thelikelihood of their occurrence. The report explores therole of animals, and in particular non-domestic animals, inemerging infectious human diseases. This is essential forour global efforts to improve our response preparedness
because the frequency of spillover of pathogenicorganisms jumping from animals to humans has been
increasing considerably, due to the growing magnitude of
our unsustainable natural resource use in today’s world.
The relationship between the environment, biodiversity,
human society and human diseases is complex.2 Whilewildlife may be a source of human disease, domesticatedanimal sources may act as amplifiers of pathogens
emerging from the wild. Moreover, as noted in this report,
most emerging infectious diseases—whether in wildlife,
domestic animals, plants or people—are driven by humanactivities such as agricultural intensification, wildlife use
and mis-use, and human-induced landscape changes,
interacting in unpredictable ways that can have negative
outcomes.
Against this backdrop, it is important to recognize thatdisease emergence is not only about the relationshipbetween domestic animals or wildlife and people, butalso about the complexity of the system as a whole andthe interactions between biotic and abiotic components.
Biodiversity, and the complexity of our landscapes andseascapes, is integral to social and ecological resilience.3
It is also important to take into account the complex
relationship between biodiversity and our mental andphysical health, including non-communicable diseases aswell as infectious diseases. The many linkages here include
those related to air, water, food security, and nutrition.2
Accordingly, the Convention on Biological Diversity has
developed a biodiversity-inclusive One Health Guidance,3
which looks at the One Health concept as a key ingredientfor conservation and sustainable use of biodiversity. The
WHO defines One Health as an approach to designingand implementing programmes, policies, legislation andresearch in which multiple sectors communicate and work
together to achieve better public health outcomes.
This science-for-policy report provides examples of theapplication of the One Health approach and related policy
response options that can be implemented by governments,
civil society and the business sector in their efforts to tackle
the drivers of zoonotic diseases with the ultimate goal tominimize the risk of future zoonotic disease outbreaks.

9

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

10

Section I | Overview of emerging infectious diseases including zoonoses

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Section One

Overview of emerging infectious diseases
including zoonoses
The emergence of the severe acute respiratory syndrome
coronavirus-2 (SARS-CoV-2) at the end of 2019 and thevast global public health and economic impacts this novel
coronavirus is causing in 2020 are treated as a crisis. While
pandemics such as this are sometimes seen as a “blackswan”—an extremely rare event—they are actually awidely predicted consequence of how people source food,trade animals, and alter environments.
To manage emerging infectious diseases (EID), including
zoonoses, and reduce the risk of them becoming
epidemics and pandemics, we need to understand their
origins, their various types and importance in different
communities, and their drivers. This section introduces thegeneral reader to emerging diseases and zoonoses, before
we take a deeper dive into the world of coronaviruses in
Section Two.

What are emerging diseases and what are
zoonoses?
People and other animals share many microorganisms
and diseases; such co-existence is natural, common andimportant to health. Only a few of these cause disease.
Considering the millions of species of microorganism on
Earth, pathogens (microorganisms that harm the host) are
extremely unusual. Only about 1,400 microorganisms are
known as potential causes of human infections.
New diseases in humans can emerge either as a resultof a change in the nature or behaviour of commensal
microorganisms that cause disease, or through infection by
novel organisms, usually through contact with animals andthe environment, where most microorganisms exist.
About 60 per cent of human infections are estimatedto have an animal origin,4 and of all new and emerging
human infectious diseases, some 75 per cent “jumpspecies” from (non-human) animals to people.5 In highincome countries, direct infection with a zoonosis isprobably a rare event,6 with most described zoonoses
happening indirectly, e.g. through insect vectors or, more
frequently, via the food system.7 Domesticated animal
species share an average of 19 (range of 5–31) zoonotic
viruses with people, and wild animal species share an
average of 0.23 (range of 0–16) viruses with people.8 So,
unsurprisingly, the vast majority of animals involved inhistoric zoonotic events or current zoonosis are domestic

Section I | Overview of emerging infectious diseases including zoonosesI(livestock, domesticated wildlife and pets), which is
logical as the contact rates are high. The emergenceof a new wildlife zoonosis is extremely rare, but can bevery significant.
Around 80 per cent of pathogens infecting animals are“multi-host,” meaning that they move among different
animal hosts,9 including occasionally humans. Domestic
animals and peri-domestic wildlife also act as bridges
for the emergence of human diseases; this can occur inan evolutionary sense, or the animal could serve as aphysical transmitter.
Some of these viruses generated in bio-insecure industrial
and intensive agricultural systems result in zoonotic
forms of the virus. An example is the highly pathogenic
avian influenza (HPAI), an important economic diseaseof domestic poultry that evolves from low-pathogenic
viruses that circulate commensally in the environment inwild bird populations. Another example is Rift Valley fever(RVF), where domestic livestock have served as amplifying
hosts for the human- and animal-pathogenic virus thatoriginally circulated between wild animals and mosquitos.
The reservoir is the wild animal, while the domestic animal
is the bridging host to human infection.
True human pandemic influenza viruses (rather like
COVID-19) have a more complex evolution with mixing ofviruses in different domestic animal compartments, usuallypigs and poultry and interacting with human influenzas toproduce highly pathogenic human influenza pandemics.
While we are in the midst of an ongoing pandemic of
COVID-19, recent decades have seen other headlinehitting and dramatically destructive novel diseases.
Amongst the more prominent examples are: zoonotic
influenza (Bird Flu), pandemic human influenza (H1N1),
Middle East respiratory syndrome (MERS), and severe
acute respiratory syndrome (SARS), most of which havea proven or suspected domestic animal involvement intransmission; only SARS has a suspected peri-domestic
wildlife reservoir, though yet unproven.
Other diseases, such as re-emerging West Nile fever,
yellow fever and Zika virus diseases are indirect zoonoses.
In recent decades, emerging diseases of zoonotic origin
have had direct costs of more than USD100 billion; it was
earlier estimated that if these outbreaks had become11Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

The bipartite network of zoonotic viruses sharing among domestic and wild mammalian hosts

VirusesPrimates
Carnivores
Rodents
Bats
Ungulates
Other wildlife species
Domestic animals
2

3

1

7
5

4
9

6
10
11

8

1 Horse (Equus ferus)
2 Cat (Felis catus)
3 Pig (Sus scrofa)
4 Dog (Canis lupus familiaris)
5 Cow (Bos taurus)
6 Goat (Capra aegagrus)
7 Sheep (Ovis aries)
8 Dromedary camel (Camelus dromedarius)
9 Llama (Lama glama)
10 Alpaca (Vicugna pacos)
11 Donkey (Equus africanus)

Johnson et al. (2020)8 analysed data on wild and domesticated mammalian species that share viruses with humans. The resulting bipartite
diagram demonstrates the association between zoonotic viruses and mammalian host species. Host species harbouring the same zoonotic
virus are linked by a virus node (). Mammalian species nodes are coloured by domestication status and taxonomic order for nondomesticated terrestrial wildlife. Species node size is relative to the zoonotic virus richness calculated in that species. Humans, who are host to
all viruses, are not shown in the diagram.
Source: Johnson et al. (2020)8 published by the Royal Society under the Creative Common license (CC BY 4.0). The diagram legend has been modified for readability.

human pandemics, the losses would have amounted toseveral trillion dollars.10 And this is likely to be the case forthe current COVID-19 pandemic. Despite the massive realand potential socio-economic impacts of emerging zoonotic
diseases, and despite the general consensus that prevention
is better than cure, investments and political will to control
them at their source have been insufficient to date.
Emerging diseases are of course hugely problematic,with some becoming epidemic (affecting a large numberof people within a region), others becoming pandemic(spread over several countries and continents andaffecting large numbers of people around the world).
COVID-19 is now a pandemic spread across the planet,sickening and killing people and sending billions into
lockdowns of various kinds as health services struggle tocope and killing hundreds of thousands by June 2020.

12

Also, of great importance to some countries and regionsof the world are endemic zoonotic diseases. The so-called“neglected zoonoses” are continuously present in affected(mainly impoverished) populations, yet receive muchless international attention and funding than emerging
zoonotic diseases.11 Among the important neglected
zoonoses widespread in developing countries are anthrax,
bovine tuberculosis, brucellosis, rabies, cysticercosis (pigtapeworm), echinococcosis (hydatid disease), Japanese
encephalitis, leptospirosis, Q fever, rabies, Lassa fever
virus and trypanosomiasis (sleeping sickness). Most ofthese are spread by domestic animals, but several have awildlife interface, or wildlife is of occasional importance(brucellosis, leptospirosis, rabies, alveolar echinococcosis
and bat-associated rabies). Only Lassa fever has exclusively
a wildlife host (the multi-mammate rat).

Section I | Overview of emerging infectious diseases including zoonoses

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Neglected zoonoses persist in communities experiencing
complex development problems—typically a mix ofpoverty, poor sanitation, poor access to water and waste
removal services, isolation, socio-political insecurity,
political marginalization, low literacy levels, genderinequality and degraded natural resources. These
communities often have a high dependence on livestockand high contact with wild or peri-domestic wildlife, which
increases their exposure to pathogens. Another often
neglected category of diseases with mainly domestic
animal origins are those that are foodborne. For poor
people, some of the responses made to control outbreaks
may inadvertently cause harm, for example by reducing
access to animal source food, important for nutrition, as aresult of large-scale culling of domestic animals.12
Remarkably, a recent study by the World HealthOrganization (WHO) found the burden of a selectionof important food-borne diseases to be comparable tothat of “the big three” major infectious diseases: HIV/AIDS (human immunodeficiency virus-acquired immune
deficiency syndrome), malaria and tuberculosis.13
Between 2018 and 2019, for example, South Africa
experienced the world’s largest outbreak of listeriosis, withmore than 1,000 laboratory-confirmed cases and morethan 200 fatalities of people who got infected after eating
contaminated food products.14

When do zoonoses become human disease
outbreaks?
Historically, the emergence of new human diseases
from animals has been associated with major societal
change. For example, during the Neolithic transition
from hunter-gathering to agricultural societies, humans
lived shorter lives, ate less and poorer-quality foods, were
smaller in size and were sicker than their hunter-gatherer
ancestors. With the advent of agriculture, the dramaticrise in population and the settlement of people in close
proximity to their waste led to increases in human disease;the domestication of animals led to livestock pathogens
jumping species into people, where they became theprobable cause of diseases such as diphtheria, influenza,
measles and smallpox.15,16
Subsequent major plagues or outbreaks, associated withmajor societal stresses and upheavals, were linked withzoonoses or diseases that had originally jumped species
from animals to people, but had subsequently become
transmitted mainly from person to person. Some of themost dramatic ones are:
1. The true zoonotic bubonic plague or pest (Black
Death caused by the bacteria Yersinia pestis) of the
mid-fourteenth century killed millions in Eurasia
and North Africa, wiping out a third of Europe’s
population.

Section I | Overview of emerging infectious diseases including zoonoses

Types of zoonotic diseases
Emerging zoonotic diseases
are those that newly appear in human populations or haveexisted previously but are now rapidly increasing in incidence or
geographical range. Fortunately, these diseases are often nothighly lethal and most do not spread widely. But some emerging
diseases have enormous impacts. Ebola, HIV/AIDS and now
COVID-19 are well-known examples of emerging zoonoses
particularly harmful to human health and the economy.

Ebolaoutbreakof 2013-2016 in
Guinea, Liberia
and Sierra
Leone

Zika virus
outbreak2015-2016 in
the Americas

11,323 deaths
USD 2.8 billion
in economic losses

1 in 7 babies of pregnant
women infected with Zika virus
develops neurological problems
USD 912,000 life-time cost
per case of Zika-associatedmicrocephaly

Epidemic zoonoses
typically occur intermittently and are mostly domestic in origin.
Examples are anthrax, leishmaniasis and Rift Valley fever.
Epidemic zoonoses are often triggered by events such as climate
variability, flooding and other extreme weather, and famines. The
overall health burden of outbreak/epidemic zoonoses is muchless than that of neglected zoonoses, but because epidemic
zoonoses cause ‘shocks’ to food production and other systems,
they can significantly reduce the resilience of affected
impoverished communities
Extended
periods ofThe
2015-2016
El Niño induced

Rift Valley
fever outbreaksin Mauritania

permafrost
thaw playeda key role in the 2016
anthrax outbreakon the Siberian
Yamal Peninsular

Neglected zoonotic diseases
are mostly domestic in origin, and continuously present to agreater or lesser degree in certain populations. These common
diseases affect mostly poor populations and are commonly
neglected by the international donor, standard-setting andresearch communities alike as well as by national governments.
It is likely that poor detection and surveillance of these diseases
diminish their recognition and hence prioritization byresearchers and policymakers.

50 million people
Impact ofpig
tapeworm

affected globally

80% of them live indeveloping countries
USD 150 million
annual cost to India

For references see page 60.

13

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Global hotspot map of estimated risk in zoonotic disease emergence

Allen et al. (2017)23 analysed emerging infectious diseases (EID) of wildlife origin based on a broad set of predictors, such as the distribution oftropical forested regions, human population density, mammal species richness, agricultural land use, and others. The resulting heat map shows
the global spatial patterns of estimated risk of zoonotic EID events after factoring out reporting bias.

2.

3.

4.

5.

Epidemics of European diseases in the Americas
shortly after the arrival of Europeans in thesixteenth century were responsible for the deathsof up to 95 per cent of the indigenous populations
and accelerated the destruction of their ancientcivilizations.17 It is thought that more infectious
diseases of the temperate zone emerged in the Old
World, compared to the New World, because diverse
species of animals capable of harbouring ancestral
pathogens were domesticated in the Old World.16
The tuberculosis outbreak of the nineteenth century,
associated with the industrialization in Western
Europe and over-crowding, killing up to one in four
people. Unlike the current situation, where mostillness is caused by non-zoonotic tuberculosis, asubstantial proportion of the nineteenth-century
outbreak was thought to be caused by zoonotic
tuberculosis.18
The expansion of colonial rule in Africa facilitatedoutbreaks of zoonotic sleeping sickness that killed
one third of the population in Uganda and up to one
fifth of the people living in the Congo River Basin in
the first decade of the twentieth century.19
The 1918 influenza pandemic killed some 40 million
people in the last months of World War I and thefollowing years (1918–1921).

The global human population has increased fromabout 1.6 billion in 1900 to about 7.8 billion today. The
population of the domesticated animals that provide
people with food, and of pests or “peri-domestic animals”(such as rats) that thrive in new environments created by

14

people, increased in parallel. In general, these exploding
human, livestock and pest populations have reduced thesize of wildlife populations while paradoxically increasing
contacts among people, livestock and wildlife (withmore people hunting fewer wild animals in diminishedand degraded ecosystems, and an increasing number ofhuman-wildlife conflicts worldwide).
However, this broad-brush picture conceals some great
regional and local differences. Some countries havedeclining rather than expanding human populations.
And over the last century, “natural environments” havereturned to depopulated rural areas (e.g., parts of thenortheastern United States) as small farms proved
unviable and farmlands reverted to forested lands.
Despite these exceptions, overall there have beensignificant increases in human populations, encroachmentof humans and livestock into wildlife habitats, andconcurrent massive decreases in natural environments.
These changes have important implications forecosystem, animal and human health alike. One of these
consequences is an increase in emerging zoonoses. Manyof these diseases are emerging in high-income settings,
but there is an increasing trend for these diseases toemerge in low- and middle-income countries.20-22
While still imperfect, our understanding of the factors
favouring emerging diseases is growing. For example, one
study makes the case that the risk of zoonotic emerging
infectious diseases is elevated in forested tropical regions
where land use is changing and wildlife diversity, in termsof mammalian species richness, is high.23

Section I | Overview of emerging infectious diseases including zoonoses

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Seven major anthropogenic drivers ofzoonotic disease emergence

Pathogen flow at the wildlife-livestock-humaninterface

A broad range of studies on zoonotic disease emergence
implicates the following seven main drivers of theiremergence.20,24-26 Many of these drivers are now occurringin the same places, amplifying their impact. A descriptionof each of these drivers is provided below.

Biosphere

Wildlife
Peri-domestic
Wildlife

1.	 Increasing demand for animal protein
High-income countries have experienced little change
in consumption of animal source foods during the last
four decades. In contrast, Southeast Asia has seen a rapid
increase: Since the 1960s, the share of the region’s daily
food supply of proteins from animal products has doubled
to 21 per cent; from fish, it has increased by half to 15 percent. The share of total calories from both fish and animal
products doubled to total of 12 per cent of the supply.
Meanwhile, South Asia has also seen an increase in animal
protein consumption, but not as strong. Sub-SaharanAfrica has also followed the pattern seen in Southeast
Asia, although it has been less marked. This per capita
increase in animal protein consumption in many lowand middle-income countries has been accompanied bysignificant growths in population. Together, these factors
have driven a strong growth in meat production (+260
per cent), milk (+90 per cent), and eggs (+340 per cent)over the last 50 years. This trend is predicted to continue inthe coming decades, with most growth in animal-source
food consumption occurring in low- and middle-income
countries. Compared with other protein sources, livestock
product consumption is rising rapidly, whereas the longterm trend for pulses is of sustained consumption levels.

2.

Unsustainable agricultural intensification

Increasing demand for animal-source foods stimulates theintensification and industrialization of animal production.
The intensification of agriculture, and in particular ofdomestic livestock farming (animal husbandry), results inlarge numbers of genetically similar animals.
These are often bred for higher production levels; more
recently, they have also been bred for disease resistance.
As a result, domestic animals are being kept in close
proximity to each other and often in less than ideal
conditions. Such genetically homogenous host populations
are more vulnerable to infection than genetically diverse
populations, because the latter are more likely to include
some individuals that better resist disease. Factory farmingof pigs, for example, promoted transmission of swine flu
due to a lack of physical distancing between the animals.27
In poorer countries, there are additional risk factors inthat livestock production often occurs close to cities,
while biosecurity and basic husbandry practices are often
inadequate, animal waste is often poorly managed, andantimicrobial drugs are used to mask poor conditions orpractices. Since 1940, agricultural intensification measures
such as dams, irrigation projects and factory farms have

Section I | Overview of emerging infectious diseases including zoonoses

HumansLivestock

Domestic landscape

Source: Adapted from Jones et al. (2013)25

been associated with more than 25 per cent of all—andmore than 50 per cent of zoonotic—infectious diseases
that have emerged in humans.28 Moreover, around one
third of croplands are used for animal feed. In somecountries, this is driving deforestation.29

3.	 Increased use and exploitation of wildlife
There are many ways in which wildlife are used and traded.
Section three provides more detail on the complexities.
However, in general, an increasing use and exploitation of
wildlife includes the following:
1. Harvesting wild animals (wild meat, sometimes called“bushmeat”) as a source of protein, micronutrientsand money for the poor;
2. Recreational hunting and consumption of wildlife as a
status symbol;
3. Consumption of wildlife in the belief that wild meat is
fresh, natural, traditional and safe;
4. Trade in live animals for recreational use (pets, zoos)
and for research and medical testing; and5. Use of animal parts for decorative, medicinal andother commercial products.
In general, use and trade in live and dead animals canlead to increased close contact between animals andpeople throughout the supply chain, which increases
the risk of zoonotic disease emergence. In some regions,as human populations and wealth have increased, there
has also been an increased demand for wild animals andtheir products. In West Africa, for example, exploitation of
wildlife for food has increased over the last 10 years.30
Infrastructural development can often facilitate wildlife
exploitation: new roads in remote areas can increase

15

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

human access to wildlife and help spread diseases within
and between countries more rapidly. As animals in thewild become scarcer, attention has turned to the farmingof some species of wild animals.31 While this might havethe potential to reduce the pressure on wildlife, farming
wildlife or “ranching” is often more costly than harvesting or
hunting animals from the wild, and less preferred by local
communities; it also may create cover for the “laundering”
of wild animals.32 In addition, any significant increase in thefarming of wild animals risks “recapitulating” the increases
in zoonoses that likely accompanied the first domesticationof animals in the Neolithic era, some 12,000 years ago.16

Encroachment into wildlife habitats that are altered
for the purpose of extracting their natural resources—
e.g., mining, oil and gas extraction, logging but also
harvesting bat guano—also encourages new or expanded
interactions between people and wildlife. These activities
often come with other changes, such as new humansettlements, road building and movements of people
and products, which further increase human access towilderness areas and often provoke changes in how local
communities acquire and store their food (e.g., via wildlife
hunting, introduction of livestock rearing, and keeping
food stocks that attract pest animals).

4.	 Unsustainable utilization of natural resources
accelerated by urbanization, land use change
and extractive industries

5.	 Travel and transportation

Rapid urbanization, especially when unplanned and withpoor infrastructure, creates novel and diverse contacts
among wildlife, livestock and people. The greater
movement of people, animals, food and trade that is
associated with accelerated urbanization often provides
favourable grounds for the emergence of infectious
diseases, including zoonoses. For example, irrigation
systems encourage some vector-borne zoonoses tospread; deforestation and fragmentation of ecosystems
and wildlife habitats encourage contacts at the humanlivestock-wildlife ecosystem interface;32 and increased
human settlements and fencing constrain herding andmigratory movements of both domesticated and wild
animals. Ecological tourism and human settlements nearcaves and forested areas, particularly those with poor
housing conditions, can increase human-wildlife contacts
and human exposure to insects, ticks and other vectors ofwildlife pathogens.
Infrastructure development, including new roads andrailways, transformation of natural areas to commercial andretail use, and other drivers of land-use change can also
contribute to the destruction and fragmentation of wildlife
habitats and increase human-wildlife contact and conflict.
Video: How can animals make you ill?
Video Link: https://www.youtube.com/watch?v=J5qLKWUTNM4 |© RIVM/Government of the Netherlands

16

Diseases can now move around the world in periods
shorter than their incubation periods (the time between
exposure to a pathogen and the first clinical sign ofillness). The increasing amounts of human travel andtrade, including the increasing handling, transport and(legal and illegal) trade of animals and animal products,
increases the risk of zoonotic diseases emerging andspreading.

6.	 Changes in food supply chains
Food supply chains are lengthening and diversifying,especially in low- and middle-income countries. This
trend—which is being driven by increased demand foranimal source food, new markets for wildlife food, andpoorly regulated agricultural intensification—is creating
additional opportunities for disease transmission. These
include the following:
1. There are increased opportunities for crosscontamination.
2. It can be more difficult to identify where a given foodcomes from. Traceability challenges make it harderfor officials to follow up quickly on any potential
problems.
3. Changes in processing can encourage theproliferation of zoonotic diseases (e.g., the formationof biofilms—microbial ecosystems—in foodprocessing plants).
4. Rapidly expanding and poorly managed informal
wildlife and fresh produce markets (including socalled “wet” markets) bring products along poorly
regulated supply chains to supply rapidly growing
cities. While traditional markets provide many
benefits, especially for poor people—including theirconvenience, lower costs, sales of traditional foods,
and support of livelihoods (especially women)—theirlevels of hygiene are often low, and biosecurity ispoor, increasing the risks of disease. The same is often
true along the supply chains from rural areas to themarkets in the cities.
5. Industrial meat processing plants can also be sitesof disease transmission. Food from modern retail
outlets is not always safer than that from informal
markets.33 For example, there have been many

Section I | Overview of emerging infectious diseases including zoonoses

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Impacts of climate change on zoonoses

Caster bean tick, deer tick or sheep tick (Ixodes ricinus) is a well-known vector of Lyme disease in Europe
Photo credit: Dagmara_K / Shutterstock.com

Climate change is a major factor in disease emergence. The survival, reproduction, abundance anddistribution of pathogens, vectors and hosts can be influenced by climatic parameters affected by climatechange. For example, climate variability tends to affect the many diseases transmitted by insects, ticks andother arthropod vectors. Warmer temperatures could also increase the incidence of disease both byincreasing the vector population size and distribution and by increasing the duration of the season in which
infectious vector species are present in the environment. Many newly emerging infectious diseases arise intropical regions where the warm temperatures suit the lifecycles of both pathogen and vector.16 The impactsof climate change on zoonotic diseases as well as on food and economic insecurity and other problems
are predicted to be harshest in low- and middle-income countries, where disease surveillance and data areparticularly scarce.37
Climate change is a force of growing importance that influences the future geographic distribution andabundance of species such as bats, monkeys and rodents, including those in which zoonotic pathogens
often originate; and of mosquitos and other vectors that transmit viruses such as the chikungunya virus andWest Nile virus. Climate change can increase or decrease the incidence of the insect-transmitted Chagas
disease, sand-fly transmitted leishmaniasis, and other vector-borne and zoonotic diseases, generally withgreater illness occurring at higher degrees of warming.38 In 2010 in Africa, an outbreak of Rift Valley fever, amosquito-borne zoonotic disease, occurred with higher than average seasonal rainfall; other outbreaks haveoccurred even with short periods of heavy rainfall.16
An extensive literature review of emerging diseases in Brazil revealed relationships between infectious
diseases outbreaks and (1) extreme climate events (El Niño, La Niña, heatwaves, droughts, floods, increased
temperature, higher rainfall), the frequency of which might be affected by climate change; and (2)environmental changes (habitat fragmentation, deforestation, urbanization, wild meat consumption).39
Arctic and subarctic regions are especially vulnerable to climate change due to the thawing of thepermafrost, which significantly transforms soil structures, vegetation and habitats. Degradation of thepermafrost can expose historic burial grounds, enabling the revival of deadly infections from the past.40
Rising temperatures are raising the risk of zoonotic diseases in the vast Republic of Sakha (Yakutia) whichmakes up one fifth of Russia’s territories. Extended growing periods and expanded habitats are providing
some zoonotic pathogens and their vectors with more favourable living conditions.

outbreaks of COVID-19 from the massive, crowded,
artificially chilled industrial meat plants in Europe
and America, but much fewer from smaller, naturally
ventilated meat plants in many low- and middleincome countries. Thus, it cannot always be assumed
that the modernization of food value chains will
reduce risk. Moreover, especially in low- and middleincome countries, people are consuming moreanimal-source foods than in the past, which results inpotential exposure to pathogens, including zoonotic
pathogens.34

Section I | Overview of emerging infectious diseases including zoonoses

7.	 Climate change
Many zoonoses are climate sensitive and a numberof them will thrive in a warmer, wetter, more disasterprone world foreseen in future scenarios.35 Somepathogens, vectors and host animals probably
fare more poorly under changing environmental
conditions, disappearing in places and resulting in
the loss of their population-moderating effects or theestablishment of other species in the new ecologicalniches created by their departure. There is some
speculation that the SARS-CoV-2 may survive betterin cooler, drier conditions when outside the body.36

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Preventing the next pandemic:
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Immunodeficiency disorders in primates

Chimpanzees in Uganda
Photo credit: CherylRamalho / Shutterstock.com

Two of the most significant zoonotic disease transmissions in recent history are the humanimmunodeficiency viruses, HIV-1 and HIV-2, the etiologic agents for acquired immune deficiency syndrome(AIDS) in humans.41,42
The closest relatives of HIV-1 are simian immunodeficiency viruses (SIVs) that infect wild-living chimpanzees(Pan troglodytes troglodytes) and gorillas (Gorilla gorilla gorilla) in Western Equatorial Africa. Chimpanzees
were the original hosts of this clade of viruses. Four lineages of HIV-1 have arisen by independent crossspecies transmissions to humans and one or two of those transmissions may have been via gorillas.43
On the other hand, the closest relatives of HIV-2 are simian immunodeficiency viruses in a monkey, thesooty mangabey (Cercocebus atys), whose natural range is in west Africa.44 SIV-HIV species crossing seemto have occurred originally at least six times between sooty mangabeys (primate) and humans.45 Sooty
mangabeys and chimpanzees are both often kept as pets and used for food, thus resulting in their frequent
direct contact with humans.46,47
More than 40 species of African monkeys are infected with their own, species-specific SIV.47-49 Theseviruses are of relatively low pathogenicity and they do not induce an AIDS-like disease in their natural
hosts, suggesting that they have associated and evolved with their hosts over an extended period of time.
However, recent evidence shows that SIVcpz can cause AIDS-like disease and reduced fertility in Eastern
Chimpanzees.50
The conclusion that HIV-1 was derived from a virus infecting chimpanzees is of particular interest, because
chimpanzees and humans are so closely related. This raises a number of interesting questions: 1) as tothe origin of the chimpanzee virus; 2) whether adaptation of SIVcpz to infecting chimpanzees madethe virus more capable of infecting humans; and 3) whether SIVcpz infection of chimpanzees is of low
pathogenicity or not.43 Based on the analysis of strains found in four species of monkeys from Bioko Island
in Equatorial Guinea, which was isolated from the mainland by rising sea level about 11,000 years ago, it
has been concluded that SIV has been present in monkeys and apes for at least 30,000 years, and probably
much longer. Therefore, it is thought that SIV may have previously crossed the species barrier into humanhosts multiple times throughout history, but it was not until relatively recently at the advent of moderntransportation and global travel that HIV spread regionally and globally beyond decimations in local
populations.51

18

Section I | Overview of emerging infectious diseases including zoonoses

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Other factors playing a role in zoonotic
disease emergence
The seven main drivers of zoonoses emergence, describedabove, are all anthropogenic, that is, the result of humanaction. Other factors, of course, also affect disease
emergence, particularly the agent type, virulence andmodes of transmission of the pathogen; the susceptibilityof the pathogen’s host; and the longevity and rangeof the pathogen’s animal reservoir. Pathogens that are
widely distributed, mutate rapidly and are multi-hostare considered most likely to jump species. RNA viruses
mostly lack the “proofreading” mechanisms of DNA viruses
and hence develop many more mutations as they evolve,
some of which may make the virus better able to infecta new host. Pathogens that spread using the respiratory
functions of the host (which are over-represented
among emerging diseases) have fewer barriers tomoving from one host to another than pathogens spread
via other routes.

Certain people are more susceptible than others to
infection with pathogens. Age, health, sex, physiology,
nutritional status, exposure history, simultaneous infection
with more than one pathogen, immunocompetence,
genetics and underlying diseases all influence anindividual’s susceptibility to infection. Certain animals,in their turn, are more likely to harbour zoonotic
or potentially zoonotic pathogens based on their
physiological characteristics, ecosystem niche, social
behaviour and relatedness to humans. Some studies
detected higher numbers of zoonotic viruses in animal
species that have become abundant and have expanded
their range by adapting to human-dominated landscapes.8
Livestock, rodents, bats, carnivores and non-humanprimates have been identified as of special concern inseveral studies. However, as with all animals, they are notrisks in and of themselves, and it is only when there isclose contact with people that there is the potential forthis risk to be realized.

Baby owls in a cage sold in an animal market in Yogyakarta, Indonesia
Photo credit: Ibenk_88 / Shutterstock.com

Section I | Overview of emerging infectious diseases including zoonoses

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20

Section II | Coronaviruses in a One Health context

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Section Two

Coronaviruses in a One Health context
In this second section, we move from zoonoses ingeneral to the specific alarming and ongoing pandemicof COVID-19, a disease caused by a zoonotic coronavirus.
The section starts with some background on
coronaviruses and continues from the One Healthperspective, reflecting both veterinary and medical
experiences and commonalities between important
coronavirus diseases and pandemics.

5.

What are coronaviruses?
Coronaviruses are a large group of viruses that infect many
animals and humans and are responsible for numerous
diseases. They are named “corona” for the crown-likearrangement of the spike-shaped proteins on the surfaceof their membranes. Some human coronaviruses usuallycause mild upper respiratory illness like the common cold.
They can also cause serious diseases such as infectious
peritonitis in cats and respiratory and enteric infections
in cattle. The only known serious human coronavirus
diseases are SARS, MERS and COVID-19, and all are likely
to have zoonotic origins. In addition to these well-known,
sporadic, locally important and long-established diseases,
there have been at least six major outbreaks of novel
coronaviruses in the last century, all of which imposedhigh costs across several continents:
1.

2.

3.

4.

Infectious bronchitis virus (IBV) causes infectious
bronchitis in poultry. It emerged in the 1930s andis still one of the main causes of economic losses in
the poultry industry, with repeated waves of diseasecaused by different strains.52
Transmissible gastroenteritis (TGE) virus was
first reported in the United States in 1946 andsubsequently spread to Europe, Africa, SouthAmerica and China.53
Porcine epidemic diarrhoea (PED) virus emerged in1971 as a pig disease causing a global pandemic ofenormous cost and is still a major problem in piglets.
Since then different strains have caused waves of
disease in Asia, Europe and the Americas.54
SARS-CoV, the coronavirus that causes severe acuterespiratory syndrome, or SARS, was first reported in
China in February 2003 and likely originated frombats, probably then spreading to other animals (likely
civet cats) and then to humans. The illness thenspread to more than two dozen countries in North
America, South America, Europe and Asia before it

Section II | Coronaviruses in a One Health context

6.

was contained. Over 8,000 cases were reported andnearly 800 people died of the disease. Since 2004
there have not been any reported cases.55
MERS-CoV, the coronavirus that causes Middle East
respiratory syndrome, or MERS, was first reported in
Saudi Arabia in 2012 and has a higher mortality rate
than SARS. MERS-CoV can occur zoonotically fromhuman contact with camels but has secondary cyclesof spread from ill people to other people throughclose contact. To date, there have been around 2,500
laboratory confirmed cases mostly human to human,of which more than one third proved fatal. Sporadic
cases continue to occur as the infection remains
present in dromedary camels.56
SARS-CoV-2, the coronavirus that causes a severe
acute respiratory syndrome known as COVID-19,
already has had its genome compared to the genetic
sequences of more than 200 other coronaviruses
from around the world that infect various animals.
SARS-CoV-2 appears to be a recent mix, or genetic
recombination, of coronaviruses.57 As a result of thisrecombination, one of the proteins of SARS-CoV-2
enables the virus to enter the cells of humans. Other
research has shown the virus to be 96 per centidentical to a previously identified bat coronavirus,
with a common ancestor about 50 years ago. It ishypothesized that this is the origin of the unknown
pathway that resulted in the transmission of SARSCoV-2 to humans in 2019.58

Family of Coronaviruses
Coronaviruses are diverse. They belong to theCoronavirinae subfamily in the Coronaviridae family.
The Coronavirinae subfamily comprises four genera:
Alphacoronavirus
Alphacoronaviruses cause
respiratory tract illnesses andcommon colds in humans, andgastroenteritis in animals.

Betacoronavirus
Betacoronaviruses affectmainly mammals, and include
those that cause MERS, SARS
and COVID -19.

Gammacoronavirus
They infect mainly avian
species and sometimes
mammals including cetaceans.
IBV is a gammacoronavirusthat causes avian infectious
bronchitis.

Deltacoronavirus
They are found primarily inbirds and some mammals.
Porcine deltacoronavirus(PDCov) recently emerged,
causing severe diarrhoea innewborn piglets.

For references see page 60.

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IIPreventing the next pandemic:
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Emergence of significant diseases caused by coronaviruses and other pathogens

1931

1971

2003

Avian infectious bronchitis

Porcine epidemic diarrhoea(PED)

Severe acute respiratory
syndrome (SARS)

Following the first appearance inthe UK, it spread to other European
countries and Asia. A highly virulent
PEDV strain emerged in 2013 andcaused nationwide outbreaks in theUS, and rapidly spread to North,Central and South American countries.
The virus is not zoonotic and posesno risk to humans, or food safety.

This pneumonia-like infection spreadfrom Guangdong, China, to more than
26 countries in Asia, Europe, North
America and South America before it
was contained. SARS-like coronavirus
has been found in horseshoe bats,suggesting that bats are natural
reservoirs.

Pathogen: Infectious bronchitis
virus (IBV)
Genus: Gammacoronavirus
Host: Chickens
Place of emergence:
North Dakota, USA

IBV causes an acute, highly
contagious respiratory disease inchickens. It can also damage thereproductive tract, causing
decreased egg quality andproduction. First documented inUSA, the disease is now prevalent
in all countries with an intensive
poultry industry.

1920

1930

1920s

Human Immunodeficiency
Virus (HIV) infection

Pathogen: HIV
Genus: Lentivirus
Natural reservoir: Chimpanzee for
HIV type 1, and Sooty Mangabey
for HIV type 2
Place of emergence: Kinshasa,
Democratic Republic of Congo
Based on genetic sequencing andhistorical records, the emergenceof HIV is traced back to 1920s in
Kinshasa, DRC. It is thought thatsimian immunodeficiency viruses(SIVs) in primates crossed over tohumans at the time, presumably
as a result of hunting and meat
consumption. SIVs then adapted
to the new human host to
become HIV.
For references see page 61.

22

Pathogen: Porcine epidemic diarrhoea
virus (PEDV)Genus: Alphacoronavirus
Host: Pigs
Place of emergence: United Kingdom

1940

Pathogen: SARS coronavirus(SARS-CoV)
Genus: Betacoronavirus
Natural reservoir: Horseshoe bats
Intermediate host: Masked civet cats
Place of emergence: Guangdong, China

1950

1970

1937

1947

1976

Pathogen: West Nile virus
Genus: Flavivirus
Host: Birds
Place of emergence: West Nile
district, Uganda

Pathogen: Zika virus (ZIKV)Genus: Flavivirus
Natural reservoir: Primates
including humans
Place of emergence: The Zika
forest, Uganda

Pathogen: Ebola virus
Genus: Ebolavirus
Natural reservoir: Unconfirmed
but likely to be African fruit batsof the Pteropodidae familyIntermediate host: Apes andmonkeysPlace of emergence: Twosimultaneous outbreaks in
Democratic Republic of Congo(DRC) and South Sudan

West Nile fever

Mosquitoes serve as disease
vectors carrying the virus from
infected birds to people andsome mammals. Humans areusually incidental and dead-end
hosts for the virus. The firstrecognized outbreak occurredin Israel in 1951, then Egypt.
The virus re-emerged in
Romania in 1996, and has
established itself in the US
since 1999. West Nile virus
belongs to the same genus asdengue virus and yellow fever
virus.

Zika virus diseaseZIKV was first discovered in a
febrile sentinel rhesus monkey
from the Zika forest, and in the
Aedes africanus mosquito fromthe same forest a year later.
The first human cases weredetected in Uganda andTanzania in 1952. An outbreakoccurred in the Yap Islands,
Federated State of Micronesia
in 2007, followed by a major
epidemic in the Americas in2015-16.

Ebola virus disease

The largest outbreak in history
occurred primarily in Guinea,
Liberia and Sierra Leone from2014 to 2016, killing 11,323
people. The virus also recently
re-emerged in eastern DRC from2018 to 2019. Case fatality ratioof Ebola varied from 25% to 90%.

Section II | Coronaviruses in a One Health context

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

?

2012

2016

2019

Middle East respiratory
syndrome (MERS)

Swine acute diarrhoea syndrome(SADS)

Coronavirus disease 2019
(COVID-19)

SADS-CoV caused severe and acutediarrhoea and vomiting in newborn
piglets. The outbreak killed nearly 25,000
piglets in Guangdong. Case fatality ratio:
90% in piglets less than five days old.
This coronavirus did not appear to jump
to humans.

SARS-CoV-2 appears to
be a recent mix, or genetic
recombination, of two coronaviruses.
Genome sequencing suggests that
SARS-CoV-2 is 96% identical to acoronavirus in horseshoe bats.

Pathogen: MERS coronavirus(MERS-CoV)
Genus: Betacoronavirus
Natural reservoir: Probably bats
Intermediate host: Dromedary camels
Place of emergence: Saudi Arabia
First reported in Saudi Arabia, MERS
has spread to 27 countries with alarge outbreak in Korea in 2015. A
study in 2018 shows high prevalenceof MERS-CoV strains in local camels
in Saudi Arabia, compared toimported camels from Africa.

1980

Pathogen: SADS coronavirus (SADS-CoV)
Genus: Alphacoronavirus
Natural reservoir: Probably bats
Host: Pigs
Place of emergence: Guangdong, China

1990

2000

1986

1994

Agent: Pathogenic prions
Host: Cattle
Place of emergence:
United Kingdom

Pathogen: Hendra virus
Genus: Henipavirus
Natural reservoir: Large fruitbats (Pteropus spp.) or
flying fox
Host: Horses
Place of emergence: Hendra,
Australia

Bovine spongiform
encephalopathy or
mad cow disease

Mad cow disease is a
progressive, fatal neurologicaldisorder in cattle. The humanform of the mad cow disease
known as variant CreutzfeldtJakob disease is linked toconsumption of beef fromcattle infected with thedisease.

Hendra virus infection

Sporadic outbreaks haveoccurred in Australia over
the years since its initial
appearance in 1994. So far,no cases have been reported
outside Australia. Case fatality
ratio is 75% in horses, and
50% in humans. Hendra virus
belongs to the same genus as
Nipah virus.

Section II | Coronaviruses in a One Health context

Pathogen: SARS-CoV-2
Genus: Betacoronavirus
Natural reservoir: Probably bats
Intermediate host: Unknown
Place of emergence: Wuhan, China

2010

2020

1996

1998

Pathogen: HPAI virus subtype
H5N1
Genus: Alphainfluenzavirus
Natural reservoir: Wild waterfowl
Host: Poultry
Place of emergence:
Guangdong, China

Pathogen: Paramyxovirus
Genus: Henipavirus
Natural reservoir: Large fruitbats (Pteropus spp.) or
flying fox
Host: Pigs
Place of emergence:
Sungai Nipah village, Ipoh,
Malaysia

Highly pathogenic avian
influenza (HPAI) or
bird flu

Nipah virus infection

First human cases found inHong Kong in 1997 were traced
back to wild and domestic
waterfowl in Guangdong in
1996. Re-emerging in Hong Kongin 2002, the virus spread rapidly
to South East Asian countries.
Over 100 million domesticatedchickens and ducks either diedof the disease or were culled tostop the outbreak in Asia.

Nipah virus emerged as a
respiratory and neurologic
disease in pigs, and then spreadto humans. A large outbreak in
Malaysia from 1998 to 1999
was followed by five outbreaks
in Bangladesh from 2001 to
2005. To control the outbreak in
Malaysia, at least one million
pigs were culled.

23

Preventing the next pandemic:
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SARS-CoV-2
membrane protein
envelope protein
lipid membrane

spike protein

full virion

virion cut in half

Nucleoprotein

close up of half virion section© Annabel Slater / ILRI

SARS-CoV-2 is an enveloped virus, meaning that its RNA is packaged within an outer lipid (fatty)
membrane. The lipid membrane is stable enough to protect the RNA from the surrounding environment,
but also able to break open inside the host cell to release the RNA. This balance means the membrane issusceptible to being destroyed by detergent.
The membrane contains several virus proteins. The large spike (S) proteins allows the virus to bind to andenter host cells. The distinctive ‘corona’ of spikes gives the virus its name.
Seven human coronaviruses have been identified so far, of which three are capable of invading deep into
the lungs and causing more severe disease. One possible reason is that the S protein of SARS-CoV-2, like
SARS-CoV (the virus responsible for SARS), binds to ACE-2 receptors on human cells. ACE-2 receptors arefound throughout the body but are particularly concentrated in the upper and lower airways of the lungs.
SARS-CoV-2 also binds to ACE2 particularly well. It is 10–20 times more likely to bind ACE2 than SARS-CoV.
The membrane (M) proteins give shape and integrity to the virus particle. They are also thought to help
assemble new virus particles inside the host cell.
The envelope (E) proteins are thought to assist virus growth and ability to cause disease. They may form
small pores that alter the properties of the host membranes, prevent M protein from clumping together,and assist in assembly of new viral particles inside the host cell.
Inside the viral envelope is the viral RNA, which is bound to the nucleoprotein (N). N proteins form a tightspiral that wraps and coils the RNA, protecting it from damage. When the RNA is first released into the host
cell, the N protein also reduces the host cell’s natural defences against the virus.
The coronavirus RNA molecule is 30,000 ‘letters’ long, making it one of the largest RNA viruses discovered.
While RNA viruses have a high mutation rate, coronaviruses also possess a genomic proofreadingmechanism. This can keep them from accumulating negative mutations that would weaken them.
Coronaviruses can also swap blocks of RNA with each other, potentially trading useful mutations.
While the new coronavirus likely originated from bats, it is not yet known whether or which mutations
allowed this jump from animals to humans. The RNA of SARS-CoV-2 is 96% similar to a virus found in a bat
in China. However, the bat virus contains key differences in its S protein, and is not able to infect humans. It
is also likely that SARS-CoV-2 viruses will contain host cell proteins from previous host cells. The virus also
makes additional proteins following host cell entry that allow it to multiply and make new virus particles.
In addition to vaccine efforts targeting the S-protein on the virus particle, these intra-cellular proteins arepotential targets for intervention.
Prepared by Annabel Slater, ILRI.
For references see page 62.

24

Section II | Coronaviruses in a One Health context

Preventing the next pandemic:
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Agricultural intensification and increased
demand for animal protein
These coronavirus disease outbreaks followed rapid
intensification of agricultural practices and systems,
and dramatic changes in the ways animals were kept
or farmed, many of which were made without proper
precautionary measures being taken. As mentioned
previously, this was a demand driven process, associatedwith increasing wealth, allowing people to consume
more animal source food. For instance, the emergenceof infectious bronchitis virus in the United States was
associated with post-World War I intensification of poultry
systems based on bird confinement (resulting in greater
stress and more frequent contacts) and new breeding
techniques (resulting in less genetic variation and disease
resistance). In addition, the transmissible gastroenteritis(TGE) virus and porcine epidemic diarrhoea (PED) virus
were associated with post-World War II increases inintensive pig production systems and a related decline
in pig health, similar to the case of industrialization ofpoultry production.
Colourized scanning electron micrograph of a cell (blue) infectedwith SARS-COV-2 virus particles (red)Photo credit: US National Institute of Allergy and Infectious Diseases

Common elements and origins ofcoronavirus pandemics
The six coronavirus pandemics named above share someof the following common elements.

Bats
Bats are natural reservoir hosts as well as vectors of many
microbes that can affect animals and people. Contact
between bats and other animals, including humans,
allows for inter-species transmission of the pathogens
they harbour, potentially resulting in disease outbreaks.
Most of the recent coronavirus pandemics have been
hypothesized to have an initial origin in bats. Morethan 200 novel coronaviruses have been found in batsand they are likely the source and natural hosts for all
coronavirus lineages.59 Bats are also associated withmany other important zoonoses such as Ebola, Nipah (viabridging with pigs or indirectly through contamination ofdomesticated plants) and very rarely rabies. Bat species
harbour at least 61 potential zoonotic viruses.60 They
can resist, provide opportunities for recombination, andspread many serious zoonoses as a result of their unique
physiological features (bats are the only mammals able
to fly), ecology and immunology. At the same time,bats provide many ecosystem services such as flower
pollination and seed dispersal for hundreds of species ofplants, and aid in controlling insect populations; they also
maintain ecosystems by providing food for predators suchas owls, hawks and snakes.61

Section II | Coronaviruses in a One Health context

Coronaviruses may be associated with wildlife harvest,
trade practices and the intensification of wildlife farming.
The latter is actively occurring in a number of countries,in which wildlife breeding and farming ventures havebeen established during the recent past.62 As wealthy
consumers tend to prefer wild-caught animals, themeat from these farms is often consumed by the rapidly
growing middle class in several parts of the world.63
There is concern that many wildlife farms are prone to lowbiosecurity and that they also enable illegally poachedwildlife to be “laundered”—presented and sold as legally
farmed animals.31 Both factors would increase the risk ofzoonotic disease outbreaks.
Video: Novel coronavirus
Video Link: https://www.youtube.com/watch?v=mOV1aBVYKGA |© WHO

SARS-CoV-2 virus particles
Photo credit: US National Institute of Allergy and Infectious Diseases

25Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Flying foxes or fruit bats (Pteropus sp.)
Photo credit: nutsiam / Shutterstock.com

MERS-CoV was associated with increases in dromedarycamel numbers and a shift from extensive to intensive
camel production systems. An analysis of potential driversof MERS-CoV emergence in Qatar suggests that thesocio-economic transformation in the last three decades
and the growing popularity of camel racing triggered
major changes in camel farming practices.64 Camels wereraised in designated camel complexes in a high-density
environment alongside the workers who fed and tookcare of them. Races and contests in the Gulf region also
required camels to travel frequently and extensively,
both across borders and within the country. These factors
played an important role in the transmission of MERS-CoVfrom camels to humans.

Traditional markets

initial emergence event leading to human infection.65,66
There is general consensus that informal markets canbe epidemiologically risky, especially those selling live
domesticated animals or live or dead wild animals andthose with poor hygiene.67,68 However, expert opinions
differ as to whether live animal markets should be
regulated more strictly, gradually upgraded with buy-infrom vendors, or banned completely in order to reduce
disease transmission risk. It should be noted that strict
regulation of food has proven difficult in governancepoor contexts and banning desired products oftenVideo: How do viruses jump fromanimals to humans?
Video Link: https://www.youtube.com/watch?v=xjcsrU-ZmgY |© TED-ED

Both SARS-CoV and SARS-CoV-2 have been associatedwith traditional informal markets or fresh produce markets(sometimes called wet markets). These markets sell freshmeat, fish and other perishable agricultural produce.
Some of these informal markets sell live poultry and otherdomesticated animals; many sell live aquatic products(fish and shellfish); and some sell live or dead wild animals.
The products can be sourced from many different places,
including from distant parts of the world.
SARS-CoV was associated with civet cats sold in informal
markets. SARS-CoV-2 has been associated with a
traditional food market where wildlife was purported tobe sold. Other studies, however, have cast doubt on the26

Section II | Coronaviruses in a One Health context

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

especially high disease burdens. These included, among
others, Wuhan in China, Lombardy in northeast Italy, NewYork City in the United States, Madrid in Spain, London in
the United Kingdom, and Rio de Janeiro and São Paulo in
Brazil.
The huge health impacts of this new coronavirus
necessarily imply enormous economic impacts. The
International Monetary Fund predicts that the global
economy will shrink by 3 per cent in 2020, a downgradeof 6.3 percentage points from estimates in January 2020.
The Fund also estimates that over the next two years,
cumulative output losses from the COVID-19 pandemic
could reach USD9 trillion.

Electron microscope image of the novel coronavirus, SARS-CoV-2(round blue spheres) in cell culture.
Photo credit: US National Institute of Allergy and Infectious Diseases

shifts the market underground.69 As mentioned earlier,informal, traditional or fresh produce markets have
many benefits for people, including low prices, ease ofaccess, the availability of preferred fresh and traditional
foods, income-earning opportunities for women, worker
independence, and attractions for tourists. However,these need to be weighed against the wider benefits tohumanity (including local people) of preventing disease
outbreaks and global pandemics. Ideally, solutions would
be found that preserve the benefits while mitigating therisks of traditional markets.

The International Labour Organization estimates that
COVID-19 will wipe out 6.7 per cent of working hours
globally in the second quarter of 2020—equivalent to
195 million full-time workers. The Chinese economy
shrank 6.8 per cent in the first three months of 2020,
the country’s first such contraction on record. With themodern global economy so closely interconnected, muchup- and downstream damage is anticipated. Among themore serious harms are the potential impacts on foodsystems, which could lead to more than a quarter of abillion people suffering acute hunger by the end of 2020,
according to the World Food Programme. Countries
highly reliant on food imports, such as Somalia, andthose highly reliant on food exports, such as Nigeria, areequally vulnerable. The impacts of this disease are alreadybeing felt across many sectors. According to UNESCO,for example, more than one billion students worldwide
missed attending school or university in April 2020.

High economic costs
The three recent human coronavirus outbreaks (MERS,SARS and COVID-19) have shown a relatively low humanpopulation mortality rate compared to historic plagues(some of which killed up to 90 per cent of the populations
affected); relatively high lethality in comparison to colds
or seasonal influenza; and intense social disruptions. All
six coronavirus pandemics (IBD, PED, TGE, SARS, MERS,COVID-19) have had high economic costs and, for somediseases, very high animal mortality rates.
As of 29 June 2020, there were more than 10 million
confirmed cases of COVID-19, including more than
500,000 reported deaths. These figures are likely to begreat underestimations of the true numbers of infections
and deaths. With medical staff and facilities in frontline
disease regions in or near overwhelm, COVID-19 may also
be responsible for many more indirect deaths due to sickpeople choosing not to seek medical care because of theirconcerns about contracting COVID-19 in hospitals or not
wanting to overwhelm health services. Reported to occurin 216 countries and territories (as of mid-June 2020) andon every continent other than Antarctica, the disease
initially concentrated in “disease hotspots” experiencing

Section II | Coronaviruses in a One Health context

A market in Guangzhou, China
Photo credit: tostphoto / Shutterstock.com

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Section III | Understanding the linkages between habitat loss, the trade and use of wildlife, and the emergence of novel zoonoses

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Section Three

Understanding the linkages between habitat
loss, the trade and use of wildlife, and theemergence of novel zoonoses
This section considers how human activity contributes tothe emergence of diseases at the environment-wildlife
interface. Building from the anthropogenic drivers
outlined in Section One, this section focuses on land-use
change and the use or exploitation of wildlife; discusses
evidence regarding the consumption, trade and otheruses of wild animals; describes the driving forces behindthese behaviours and actions; and focuses on the specificrisks associated with wildlife use and consumption.

Habitat and biodiversity loss
The FAO Global Forest Resources Assessment 2020
indicates that deforestation continues globally at a rateof 10 million hectares a year.70 Rapid increases in theworld’s human population from around one billion two
centuries ago to over 7.8 billion today, has meant more
and more encroachment of humans into natural habitats,which has brought humans and animals into ever-closer
contact and increased the risk of animal-to-humandisease transmission. Deforestation, particularly in tropicalregions, has been associated with an increase in infectious
diseases such as dengue fever, malaria and yellow fever,to name a few.71 This section discusses the association
between habitat/biodiversity loss and the emergence of
zoonotic diseases.
Anthropogenic land-use changes in Australia havecontributed considerably to the rise of emerging andre-emerging mosquito-borne diseases, while forest
fragmentation has increased the risk of humans
contracting Lyme disease.32,72 An examination of
circumstances surrounding outbreaks of rodent-borne
haemorrhagic fevers suggests that anthropogenically
disturbed, low-diversity habitats present the greatest riskfor humans to contract hantaviruses, causing potentiallyfatal illnesses, or arenaviruses, which cause Lassa fever
and other illnesses.73 Rodent populations are increasing
in many areas. One explanation for this is that many
predators that fed on rodents no longer inhabit disturbed
habitats. An increase in the transmission of flea-borne
diseases via small mammals due to human disturbance ofhabitats has been shown in several ecosystems.74 A studyof zoonotic malaria, transmitted by macaques in Malaysian
Borneo, confirmed the link between zoonotic spillovers
and deforestation but showed complex and different
effects of forest degradation at different scales.75 In
general, increases in malaria prevalence may be associatedwith certain forms of landscape conversion, such as partial
draining of wetlands, shrub height changes favoured bycertain species, and changes in mosquito prey that affectmosquito abundance.
Several hypotheses attempt to explain the association
between habitat or biodiversity loss and emerging
infectious diseases. First, disturbed habitats often favour
opportunistic or generalist species that happen to bereservoirs for viruses. Second, through a process called
the “dilution effect,” more virus transmission events occur
within a single species in communities that have low
species diversity than in communities that have greater
species diversity. In such cases, the single species is usuallyan opportunistic species that is the specific host of thevirus. The dilution effect occurs because communities
with more species dilute transmission events by reducing
the number of susceptible animals. For example, in
communities of higher biodiversity, disease-transmitting
vectors feed on a larger variety of hosts that are poor
reservoirs for the pathogen (e.g., West Nile virus andtick-transmitted Lyme disease).76 Nonetheless, ecologicalsystems are complex, and empirical evidence for the
dilution effect hypothesis has been inconsistent. The
outcome depends on the pathogen transmission mode,
among other factors. Dilution effects occur for mostfrequency-transmitted pathogens and amplification
effects occur for density-dependent pathogens.77
Moreover, while more biodiversity means greater viralrichness, the risk of pathogen spillover stems fromincreased exposure, for example as more humans visit
environments where pathogens are present.23,78

Hunter prepares Bonobo bushmeat over a fire in Kilima, DR Congo
Photo credit: © Terese Hart / Flickr License CC BY-NC 2.0

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III

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Respiratory infections and primates

A bonobo (Pan paniscus) in a forest of DR Congo
Photo credit: Sergey Uryadnikov / Shutterstock.com

Human respiratory pathogens have been transmitted to wild great ape populations many times, sometimes
causing extensive ape mortality. Some of these pathogens tended to cause mild disease in adult humans
but severe and even lethal outcomes in great apes, such as the human respiratory syncytial virus (HRSV)
and human metapneumovirus (HMPV), as well as human coronavirus subtype OC43 infections of wild
chimpanzees in 2016.79,80
Whether ape morbidity and mortality associated with the new coronavirus, SARS-CoV-2, could be similar tothat in humans is unknown. The fact that mild cases occur in humans is cause for grave concern for the great
apes because asymptomatic visitors could pass the virus on to great apes.81 Governments, policymakers,
conservationists, researchers and great ape tourism professionals are being encouraged to take actions
to reduce the risk of SARS-CoV-2 being introduced in endangered ape populations. Many protected areaauthorities in Africa and Asia have already taken action, with tourism suspended at almost all great ape
sites. The Primate Specialist Group, Section on Great Apes, and the Wildlife Health Specialist Group of theInternational Union for the Conservation of Nature (IUCN) refer in a joint statement of 15 March 2020 to bestpractice guidelines for great ape disease control and tourism.82,83
Other diseases have had devastating impacts on both humans and great apes. Ebola, discovered in 1976
in the Democratic Republic of Congo and in South Sudan, can afflict chimpanzees and gorillas as well as
people. Pre-2005 Ebola outbreaks occurred deep in the rainforest biomes but subsequently shifted to moretransitional forests in Uganda, DR Congo and Guinea, where forest loss might have played a role.84,85
Previous Ebola outbreaks in Gabon and the Republic of Congo in the mid-1990s killed more than 90 per
cent of the gorillas and chimpanzees in some areas, and additional outbreaks in these countries from 2000
to 2005 killed thousands of great apes.86 It is estimated that it will take gorilla populations that experienced
95 per cent mortality more than 130 years to recover.87

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Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Another hypothesis, known as the “coevolution effect,”which is rooted in ecology and evolutionary biology,
proposes to explain the underlying mechanisms that drive
this association between habitat or biodiversity loss andemerging infectious diseases.88 This theory suggests thatas humans alter landscapes and former intact habitats are
lost, forest fragments serve as islands harbouring wildlife
hosts of pathogens that undergo rapid diversification,
leading to greater probability that one of these pathogens
will spill over into human populations, where they willcause new disease outbreaks.88,89 Maintaining healthy,
well-connected ecosystems is important for migratory
and resident species and also should help reduce theprevalence of infectious diseases.89
Viral diversity is also associated with species diversity.78
New research has predicted high rates of mammalian viralsharing in the tropics, particularly among rodents andbats, depending on their taxonomic similarity and overlap
in geographic range.90 While the specific transmission
mechanisms may differ by pathogen and interaction, theshared drivers of biodiversity loss, ecosystem change anddisease emergence reinforce how biodiversity and wildlife
conservation can play critical roles in protecting humans
from emerging infectious diseases.

The roles of wildlife harvesting, farming
and trade in pathogen spread
As noted above, wild animals are hunted and captured forhuman subsistence, for recreation and for the sale of bodyparts and their derivatives.91,92 They are also farmed for the
production of food and products.

Wild meat hunting
Hunting has been part of many cultures for millennia.
However, an important disease transmission interface
between the environment and people is through theharvesting of wild animals.
It is estimated that about 6 million (metric) tonnes of wild
meat is harvested annually in Latin America and Africa.93
One analysis found that, in Central Africa, meat supply
from wild meat hunting might be higher (at 48g perperson per day) than supply from domesticated animals(34g per person per day).94 A recent survey of nearly
8,000 rural households in 24 countries across Africa, Latin
America and Asia found that 39 per cent of households
harvested wild meat and almost all consumed it.95 Animals
that are often hunted for meat include large herbivores,
primates, rodents, snakes and other reptiles. Mammals
represent more than 90 per cent of the wild meat sold inmarkets in Central Africa.
The hunting of aquatic species has taken place forgenerations, but it is clear that many poorer coastal
communities are becoming newly reliant on aquatic
wild meat to satisfy their daily dietary requirements.
These communities have also turned to this harvest foralternative sources of income.96
Aquatic wild meat includes products derived from aquatic
mammals and reptiles, including species of dolphins,
whales, manatees, crocodiles and turtles, that are used forsubsistence food, bait for fisheries and traditional uses.
The products include shells, bones and organs as well as
meat. Aquatic wild meat is obtained through unregulated,and sometimes illegal, hunts as well as from stranded(dead or alive) animals or through “bycatches” of nontarget animals caught by fishermen incidentally.

A leopard cat sold in a market
Photo credit: MemoryMan / Shutterstock

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Preventing the next pandemic:
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Migratory species and zoonotic diseases

Wild ducks
Photo credit: aaltair / Shutterstock.com

Zoonotic pathogens are found in a variety of migratory species of wild animals (e.g., bats, ungulates, andwaterfowl). While some zoonotic diseases in humans appear to have been tied to spillovers from migratory
species, most of these events have resulted from human activities, such as direct consumption of wild
animals, harvesting, handling and increased proximity of humans and livestock to natural habitats.
In the case of the current pandemic, while a bat species is a likely reservoir of the precursor to SARS-CoV-2,
there is wide consensus that bats do not carry or transmit COVID-19 to humans. Misinformation has led toan unfortunate culling of bat populations in some parts of the world.
Some migratory species have been associated with the spread of zoonoses. Yet migration has also beenshown to reduce transmission in some species.97 In particular, reduction of length or suppression of
migration has been associated with increased load in pathogens.98 As climate change and habitat loss andfragmentation are profoundly affecting migratory behaviour, there is an urgent need to further investigate
links between animal migration and disease infection dynamics.99
The conservation status of many migratory species is declining worldwide. Many factors related to theincreased occurrence of zoonotic diseases are the same as those that threaten the survival of migratory
species.
A preliminary analysis of the status of migratory animals listed under the Convention on Migratory Species(CMS) identified consumptive use as the threat affecting most species.100 Consumptive use includes both
legal and illegal trade, illegal killing, subsistence harvesting and recreational hunting. Overexploitationof wildlife has also been associated with an increased risk of pathogen spillover.8 Habitat loss andfragmentation is another major cause of migratory species decline. The loss of ecological connectivity,
vital for migratory species, is of particular concern. Habitat loss and fragmentation have also been foundto increase the likelihood of a spillover.101 Maintaining healthy, well-connected ecosystems is important for
migratory species and also should help reduce the prevalence of infectious diseases.89
Prepared by the Secretariat of the Convention on the Conservation of Migratory Species of Wild Animals.

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Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Driving forces of wild meat consumption
The increasing consumption of wild meat in certain
regions is driven by the following factors: 92,102
1. An increasing human population is demanding more
protein-rich food and income that cannot be met
with traditional resources—land, labour, livestock,capital—alone. Global population densities are
increasing, especially in Africa, which has the world’s
highest rate of population growth and is expected toaccount for more than half of the world’s population
growth between 2017 and 2050.103
2. Local communities have few incentives to conservewildlife and wildlife habitats, and there are few
attractive substitutes for these wildlife resources. In
many cases, development projects such as chicken
and pig farms have provided employment andanimal protein to local communities, but failed toreduce pressure on populations of wild species.104
In other cases, attempts to introduce domesticatedanimals into communities were unsuccessful. The
wild meat trade also serves as a safety net in times ofhardship, as it generates both protein and income forpoor households.105
3. In some regions, there is a growing demand forwild meat among wealthy urban elites, for whom
consumption of wild animals is a status symbol or aluxury good—or they simply prefer the rich taste. A
survey estimated that around 83 per cent of sampled
households in Brazzaville, Republic of the Congo,
consumed wild meat.106 Less well-off city dwellers
may also prefer wild meat, perhaps choosing lessexotic or less expensive types.
4. Increasing connectivity between rural and urban
populations is increasingly bringing poor and richworlds together. In Asia and Africa, much wild meat
as well as live wild animals are sold in informal
markets. The lack of adequate biosafety measuresmakes these markets, where live wild animals are
mixed together for their sale, a particular risk forzoonotic disease emergence.
Wild meat farming and ranching
Over the last 60 years, wild meat production fromboth illegal and legal production of farms has beensteadily increasing. Wild meat is also harvested from
more extensive production systems in rangelands inthe tropics, temperate regions and the arctic. The total
global legal production reached 2.11 billion (metric)
tonnes in 2018. In South Africa, wild meat contributes
nearly USD500 million (ZAR9 billion) annually to thecountry’s GDP and employs over 100,000 people
while also providing a considerably better return on
investment than livestock production.107 In Europe,
the value of game meat (including deer and boar) was
USD347 million (EUR321 million) in 2014. In 2006 nearly
20,000 wildlife breeding and farming ventures were
established in China.62 Game meat also contributes

significantly to local livelihoods and food security aroundthe world.97,108-111 In these cases, using and trading wildlife
is an economically viable land-use option that helps tokeep habitats intact.
There are also concerns about zoonotic disease transfer
to humans from both wildlife farms and more extensive
rangeland management systems. In theory, wildlife farms
could provide proper sanitary conditions that reduce
the risk of disease transmission. But in reality, the risk of
disease transmission with wildlife farms is significant andmore efforts to reduce risks are needed.31,112
Wildlife trade
Live animals and animal products are brought into
close proximity with people in different forms, as partof national and international legal and illegal wildlife
trades—as food, sale items, pets or medicines.112 A mix
of animal species are traded in markets—wild, captivebred, farmed and domesticated—in transport vehicles
and in market cages. Viruses transmitted to people during
practices that facilitate the mixing of diverse animal
species such as in markets have been shown to havesignificantly higher ‘host plasticity’—a taxonomically andecologically diverse host range.113
The close contact between humans and different speciesof wildlife in the global wildlife trade can facilitate animalto-human spillover of new viruses that are capable ofinfecting diverse host species. This can trigger emerging
disease events with higher pandemic potential because
these viruses are more likely to amplify via human-tohuman transmission, and thus spread widely.

Dried Tokay gecko (Gekko gecko) traded for traditional medicine
Photo credit: Orvar Belenus / Shutterstock.com

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Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Zoonotic risks of wildlife use, trade andconsumption
The potential health risks of harvesting, trading andconsuming wild meat and of trading live animals are
discussed in more detail in the following paragraphs.
Disease transmission can occur through direct contact
with any of the following:
1. Hunted and consumed wild animals;
2. Traded wild animals (including at markets);

Forest destruction anddisturbance increase human
exposure to zoonotic disease
reservoirs. A spillover of
ebolaviruses to humans is more
likely to occur in highly disturbed
forested areas. An analysis oflarge-scale deforestation andfragmentation in West andCentral Africa from 2001 to 2014shows that the Ebola virus
outbreaks along the edge of theforest was associated with the lossof the dense forests, especiallythose with high canopy cover,that happened within theprevious two years.

A study of the effect of landscapefragmentation in Brazil’s Atlantic
Forest found that the reemergence of Chagas disease,caused by the parasitic protozoan
Trypanosoma cruzi, was associatedwith reduced mammal diversity
and increased abundance ofcompetent reservoir species, suchas the common opossum andother marsupials. Moreover, T.
cruzi was found to be moreprevalent in small mammalian
species in forest fragments thanin continuous forest.

3.
4.

Wild animals kept as pets or in zoos, sanctuaries orlaboratories (not covered in this report); andDomestic animals (covered in Section One).

With wild vertebrates being reservoirs of a large repertoireof zoonotic pathogens, wild meat harvesting and tradein live animals enhances several pathways of zoonotic
pathogen spillover. Hunters in many forested regions risk
disease if injured by an animal during its capture, whencarrying their prey back home, or if they cut themselves

Habitat disturbances can alter the
dynamics of cross-species
pathogen transmission. Whenscientists examined Escherichia
coli bacteria in humans, livestock
and wildlife near Kibale National
Park in Uganda, they found that
E. coli from humans and livestock
were genetically more similar to
those collected from primatesliving in forest fragments, than thebacteria from primates living
nearby in undisturbed forest
areas. Another study in Bwindi
Impenetrable National Park also
found that E. coli from gorillas withfrequent human contacts were
genetically similar to E. coli frompeople and livestock.

Encroachment of natural habitats
brings people into greater contact
with wildlife, allowing pathogens
to jump from wildlife hosts to otherspecies. The emergence of batassociated viruses in Australia
including Australian bat lyssavirus,
Hendra virus and Menangle virus islinked to agricultural and urban
development. Bats are sensitive tohuman disturbances. Landscapetransformation and fragmentation
reduced feeding and roosting
habitats of Pteropus sp. fruit bats or
flying foxes, driving them to search
for alternative feeding and roostingsites in peri-urban landscapes.

For references see page 63.

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Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

when butchering the animal.114 These facilitate the transfer
of body fluids from the animal to the hunter.115
Investigations into the diversity of human T-lymphotropic
virus (HTLV) among Central Africans reporting contact
with non-human primate blood and body fluids throughhunting and butchering showed that these hunters were
infected with a wide variety of HTLVs associated withmany human illnesses.116 A study found simian foamy virus
infections in Central African hunters and concluded thatRodents are associated with morethan 80 zoonotic diseases. They
are highly adaptable to habitat
disturbances. A meta-analysis of
58 case studies from eight
countries suggests that land usechange is more favourable torodent species that harbour
zoonotic pathogens. Reservoir
rodents were found to be moreabundant in modified habitats,and more non-reservoir rodents innatural habitats. Experiments in asavanna system show that rodent
abundance increased when large
wildlife— either rodent predators
or competitors—were removed,
leading to an increased risk ofrodent-borne disease.

West Nile virus was introduced to
the United States in 1999 and is
now endemic. Wild andperi-domestic birds serve as virus
hosts, and mosquitoes as disease
vectors. The introduction of theexotic virus has substantiallyreduced numbers of native bird
populations, with some species
showing no signs of recovery. A
national-scale study found thatprevalence of West Nile virus
infection in vector mosquitos andhumans increased as bird diversity
decreased. Bird communities withrich diversity tended to be lesscompetent pathogen reservoirs.

retroviruses can cross into human populations via contact
when hunting and butchering.117 An extensive survey ofthe prevalence and genetic diversity of SIVs in primate
wild meat provides insights into the risk for potential new
cross-species transmissions.118
It is noteworthy that Ebola in Central Africa was spreadamong hunters opportunistically harvesting and handlinginfected gorilla and chimpanzee cadavers for meat
consumption.119 While there is a risk in consuming wild

Land-use change can facilitatecontact between species thatusually have little or no priorinteraction, allowing pathogens tocross the species barrier. Nipah
virus emerged from a large
intensive pig farm in Ipoh,
Malaysia, in 1997. Studies suggestthat Nipah virus spilled over topigs from infected fruit batssearching for food in cultivatedfruit orchards adjacent to the pig
farm. Infected pigs were thensold to other commercial pig
farms in the south, resulting in
the 1998-1999 outbreak in pigs
and piggery workers.

Changes in the pathogens canoccur as they evolve to exploit
new hosts or adapt to changing
evolutionary pressures.
Antimicrobial resistance is theresult of pathogens being exposed
to antimicrobial drugs and building
resistance over their short-lived
generations. Antimicrobials arewidely used, or misused, in
veterinary medicine, often as
preventives. Drug resistance is
growing in domesticated animals,
especially in industrialized
agriculture, and can increase risksof disease emergence in livestockand humans.

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Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Video: Hotbed of Disease
Video Link: https://www.youtube.com/watch?v=9kGH7iC-7TQ |© Frontline PBS

Bwindi Impenetrable National Park, Uganda
Photo credit: Travel Stock/Shutterstock.com

meat without applying minimum hygiene rules, this is
not the only factor. The biggest Ebola outbreaks in West
Africa and now Eastern DR Congo are about secondary
epidemiological cycles, which underscores the fact thathuman conditions and actions, not “chance spillovers,” arethe central factor in zoonotic disease transmission. In lowdensity and widely dispersed human communities, Ebola
was a sporadic, low-impact (if distressing) disease of little
socio-economic consequence until it found its way into
urban spaces with their dense, and densely connected,
human populations.

The pathogen transmission pathway from a wild animal
to a human—starting with a small number of rural
hunters and moving to large numbers of wild-meatconsumers, in both rural and urban areas, is an importantfactor.112,120 Recent studies conducted in the western partof the Serengeti, in Tanzania, showed that regardless of
the wildlife species, the samples of wild meat screened
had DNA signatures of potentially dangerous zoonotic
pathogens such as Bacillus, Brucella and Coxiella spp.121
The meat samples screened were from the highly
preferred large mammals such as buffalo, wildebeest,
eland, gazelle, giraffe, warthog and zebra, as well as
porcupine. Infections from such endemic pathogens
generally do not develop into epidemics, but such
infections can be used to identify risk pathways that
could be used by pathogens of higher consequence.
A risk assessment of zoonotic disease in markets in
Cambodia found that the combination of high wildlife
volumes, high-risk taxa for zoonoses and poor biosafety
increases the potential for pathogen presence andtransmission.122 In North America, several studies havedocumented the potential disease transmission pathway
associated with the import of live animals in trade.120,123
The first reported occurrence of monkeypox outside
Africa, in 2003, was due to human infection by pet prairie
dogs that had become infected by African rodents
imported to the US.124 In 2017, an outbreak of Salmonella
Agbeni infections was linked to pet turtles.125

Camels at the camel sales market in Cairo, Egypt
Photo credit: Buhairi Nawawi / Shutterstock.com

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Section III | Understanding the linkages between habitat loss, the trade and use of wildlife, and the emergence of novel zoonoses

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Early warning systems and monitoring wildlife

Bat research at Joshua Tree National Park in California, United States
Photo credit: US National Park Service/Hannah Schwalbe

Animal and environmental indicators can provide a valuable tool for disease early warning systems:
Monitoring microbial diversity in wildlife, either in a given region or certain species, can be a good indicatorfor detecting potential disease outbreaks, particularly for coronaviruses, filoviruses and paramyxoviruses.
Consistent monitoring of wildlife morbidity or mortality events can also provide indicators of active
circulation of disease or outbreaks. For example, an investigation of dead howler monkeys found near awildlife sanctuary in Bolivia led to the detection of yellow fever virus. This provided vital alert information
and activation of vaccination campaigns to prevent human cases.126
Sentinel surveillance approaches that select a smaller and targeted group of health workers to gather data
have been utilized effectively to get ahead of potential spillover events for the detection of West Nile virus
in birds and equids, Ebola virus in great apes, and monkeypox in chimpanzees in Cameroon.
Targeted environmental indicators may also be useful for forecasting risk alerts. Examples have included
prolonged periods of rainfall, which are associated with elevated risk of Rift Valley fever outbreaks in someregions, or flooding events, which are associated with leptospirosis. As certain species are known to serve as
hosts or transmitters of zoonotic diseases, monitoring species distribution can offer important indicationsof potential risks to human health. For example, a change in species range or introduction of invasive
species that has the potential to serve as a host can signal potential risks. Consistent monitoring andsharing of this information among wildlife, livestock and human health agencies is important to improverisk assessment and prevention for zoonotic disease threats.
There are other examples of zoonotic diseases known
to be transmitted by aquatic animals. If left untreated,zoonoses transmitted from seals, whales and other marine
mammals that rely on marine ecosystems can induce
life-threatening systemic diseases that could pose publichealth risks. Consumption of raw or undercooked meatfrom pinniped (seal, walrus) or cetacean (whale, dolphin,
porpoise) mammals has caused serious bacterial (e.g.
salmonellosis and botulism) and parasitic (trichinellosis andtoxoplasmosis) diseases in humans.96

While this section focuses on the direct risks of zoonotic
disease transmission faced by humans in contact withwild animals, there are also significant secondary impacts
to such wild animal-human interactions. As noted at the
beginning of this section, where wild animal trade isunsustainable and wildlife populations are significantly
reduced or made locally extinct, that ecosystem loses
not only its biodiversity but also a protective “biodiverse
buffer” against the emergence and spread of novel
zoonotic diseases.

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Section IV | Managing and preventing zoonoses: How One Health can help

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Section FourManaging and preventing zoonoses:
How One Health can help

The One Health approach to controlling
zoonoses

H U MA N HE

Though both One Health and EcoHealth approaches
sit at the nexus of human, animal and environmental
interactions, they have subtle differences: One Health, as
generally practiced, emphasizes biomedical animal andhuman health, while EcoHealth pays more attention to
the broader relations between health and ecosystems,
focusing on the environment and related socio-economic
systems.128 A third concept, “Planetary Health,” focuseson human health in relation to global sustainability.129
As none of these terms has an agreed or standardized
definition, and given their convergence and similarities130,
this assessment report adopts One Health as the umbrellaterm, as it can be most easily understood by decisionmakers and the general public.
As we have seen, zoonotic diseases involve and affecthuman health, animal health and environment health.

One Health

EN

TH
AL

Humanity’s experience in public health over the past
centuries allows us to draw some broad lessons about
effective management of zoonoses. As explained earlier
in this report, the One Health approach can be defined as
the collaborative effort across multiple disciplines to attain
optimal health for people, animals and the environment.
This approach has emerged as a key tool for preventing
and managing diseases occurring at the interface ofhuman, animal and environment health. At the same time,a closely related approach, known as “EcoHealth” has been
defined as a set of systemic, participatory approaches
necessary to understanding and promoting both healthand well-being in the context of social and ecologicalinteractions. Both the One Health and EcoHealthapproaches emphasize multidisciplinary collaboration forholistic interventions that attain not only human healthgoals but also animal and environment health targets, thelatter two of which are central to improving the controlof neglected and emerging infectious diseases, many ofwhich are zoonoses.127

IV
TH
O N M E N T HEAL

One Health

VIR

This section sets out the One Health approach as themost promising way to manage and prevent zoonoses;
it also gives examples of its past successes and discusses
some of the potential barriers to a wider uptake. Lessons
from managing previous zoonotic outbreaks, including
pandemics, are shared and discussed.

AN

IM A L H E A LT H

The pathogens originate in animals, and the emergenceor spillover of the diseases they cause in humans is usually
the result of human actions, such as intensifying livestock
production or degrading and fragmenting ecosystems,
or exploiting wildlife unsustainably (see Sections One
and Three). As such, their management should be intersectoral. At the global level, three intergovernmentalorganisations, from different sectors, have specificmandates that address zoonotic diseases: the World
Health Organization (WHO), the World Organisation
for Animal Health (OIE), and the Food and Agriculture
Organization (FAO).
In response to the bird flu (HPAI) pandemic, these threeintergovernmental organisations along with UNICEF, theUnited Nations System Influenza Coordination (UNSIC),
and the World Bank developed a strategic framework
for reducing the risks of emerging zoonoses.131 This
framework has five strategic elements that remain
relevant today:
1. Build robust and well-governed public and animal
health systems compliant with the WHO International
Health Regulations (the amendment entered into
force in July 2016) and OIE international standards
through the pursuit of long-term interventions.
2. Prevent regional and international crises bycontrolling disease outbreaks through improved

Section IV | Managing and preventing zoonoses: How One Health can help

39

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

national and international emergency response
capabilities.
Promote wide-ranging collaboration across sectors
and disciplines.
Develop rational and targeted disease control
programmes through the conduct of strategic
research.
Better address concerns of the poor by shifting the
focus from developed to developing economies,
from potential to actual disease problems, andthrough a focus on the drivers of a broader range of
locally important diseases.

United Nations Environment Programme (UNEP), someMultilateral Environmental Agreements (MEAs) and theWorld Bank. The Convention on Biological Diversity has
developed Biodiversity-inclusive One Health Guidance.133
And there are many other organisations, institutes,
programmes, government agencies and nongovernmentalorganisations working in this space. CGIAR, for example, isthe world’s largest global agricultural innovation network;
one of CGIAR’s constituent centres, the International
Livestock Research Institute (ILRI), has programmes
working on livestock and human health and sustainable
livestock systems.

In 2010, FAO, OIE and WHO started collaborative work toaddress risks at the human-animal-ecosystems interface
as described in the FAO/OIE/WHO Tripartite Concept
Note.132 In 2019, they updated their joint 2008 tripartite
guide on zoonoses and other One Health issues. Other
intergovernmental organisations also have interests inenvironment, animal and human health, notably the

In general, environment health initiatives have been lesswell represented than animal, livestock and human healthinitiatives in global zoonoses prevention and control
programmes. But the environment is key to the emerging
One Health approaches that are spearheading zoonoses
risk reduction and control at regional and national
levels. Applying these multi-sector approaches has had

3.
4.
5.

Role of environmental health and its practitioners in Uganda’s One Health programmes

A butcher shop in Kampala, Uganda
Photo credit: Black Sheep Media / Shutterstock.com

Environmental health practitioners in Uganda have significantly helped to reduce sickness and deaths
caused by zoonotic disease outbreaks such as Ebola. These practitioners work at the frontlines of disease
surveillance. Their tasks include the following:
•
•
•
•
•
•
•

Inspecting livestock before slaughter as well as the meat in slaughterhouses and butcheries;
Monitoring the destruction of condemned meat;
Investigating zoonotic disease outbreaks and monitoring disease control programmes;
Ensuring the control of disease vectors and vermin such as rats, fleas, mosquitoes and monkeys;
Providing communities with health education on pertinent issues such as vaccination of children
and pets;
Involving themselves in all matters related to food safety; andHelping to enforce Uganda’s public health legislation.

In short, Uganda’s environmental health practitioners are the very embodiment of the One Health approachto healthy people, animals and the environment. To stop disease outbreaks in the future, Uganda will be
relying on this remarkable group of “environmental health activists” to advise on, plan, implement, manage
and monitor the country’s many One Health activities.134

40

Section IV | Managing and preventing zoonoses: How One Health can help

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

some notable successes, such as in controlling rabies in
the Serengeti ecosystem in Tanzania; understanding thehuman and animal burden of brucellosis in Mongolia;
elucidating the transmission dynamics of Rift Valley fever
and forecasting its outbreaks; and building capacity in One
Health disease control in Southeast Asia.135

Track record in managing zoonoses
There have been many cases of successful management ofendemic zoonotic diseases. Several developed countries
have succeeded in reducing zoonotic foodborne diseases
over relatively short periods by instituting control
mechanisms all along the food value chain, with anemphasis on reducing disease in the animal host.
Similarly, many campaigns have managed to reduce
endemic zoonoses such as pig tapeworm and rabies. For
example, preventable epilepsy in humans caused by
the parasitic pig tapeworm, which is ingested by people
consuming pork in Madagascar, is being effectively
controlled by combining a roll-out of anti-worm
medication and educational campaigns. It is important toemphasize that such successes in disease control need tobe sustained: If the control measures are not maintained,
the diseases will recur after an initial suppression. For
this reason, several high-priority zoonoses have beentargeted for “progressive control towards elimination”(where possible), including HPAI, pig tapeworm andrabies. Much progress has been made in reducing or eveneliminating zoonoses from richer countries; considerable
achievements have been made in less wealthy countries
as well. In Bangladesh, for example, a canine rabies
elimination programme has focused on dog bitemanagement and mass dog vaccination since 2011; as aresult, human rabies deaths in the country have been cut
in half.
The track record in managing emerging zoonoses is much
more mixed. The rapid containment of SARS is considered
to be one of the biggest success stories in public healthin recent years. In 2003, the WHO alerted the world thata severe acute respiratory syndrome (SARS) of unknown
cause was rapidly spreading from southern China. Within
six months, this entirely new disease had been identified
as a coronavirus, with its transmission and risk factors
elucidated, treatments developed and the disease
spread stopped.
The more recent Ebola epidemic in West Africa, however,shows how difficult it can be to control a zoonotic
outbreak. The 2013–2016 Ebola outbreak at theintersection of Guinea, Liberia and Sierra Leone affected
some of the world’s poorest and least developed countries.
The outbreak grew larger than all previous outbreaks
combined, with the virus reportedly infecting 28,646
people and killing 11,323 of them. It took more than threemonths just to confirm that Ebola was the cause of many
severe illnesses and untimely deaths in the region, and bythen large numbers of people were already infected. War,
population growth, poverty, suboptimal communications
and community engagement, and poor health infrastructure all likely contributed to the unprecedented
spread, duration and size of the epidemic.136 Even when
individual epidemics are successfully declared over, thethreat of recurring spillover events will remain as long as a
strategy to address disease risks at their source is lacking:Since Ebola viruses were first detected in 1976, there havebeen approximately 30 known outbreaks.
With rapidly advancing information and communication
technologies, a surge in novel surveillance and reporting
tools is drawing on a wide range of field reports. These
tools include the Program for Monitoring Emerging
Diseases (ProMed), GeoChat, the Global Early Warning
System for Major Animal Disease Including Zoonoses(GLEWS), the Global Outbreak Alert and Response Network(GOARN), the World Animal Health Information Database(OIE/WAHIS) and Interface (currently being updated),the Emergency Prevention System for Animal Health(EMPRES-AH), and HealthMap. Although wildlife diseases
are included in several of these systems, wildlife disease
monitoring and reporting remains highly limited at
global and national scales. There is a need for information
systems for wildlife disease and pathogen surveillance
information, paired with effective connections to publichealth and domestic animal health systems to ensure
effective coordination and timely use of information.
Advances in biotechnology and molecular epidemiology
have made it much easier to develop diagnostics that canidentify and track the transmission of zoonoses as well as
support the development of vaccines and therapeutics.137
Another noteworthy trend is the democratization of
disease control. Increasing participation in zoonotic
disease control from an increasingly wide range of
people—including “community animal health workers”
and “citizen scientists”—has introduced new perspectives
and agendas to the disease control community, such as
ensuring animal welfare and assessing the impacts of bothdisease and disease control programmes on women andpoor farmers.
For example, gender plays a significant role in shaping
both infectious disease outbreaks and our responses tocontrol them. Biological, economic, cultural and politicalfactors influence how men and women are affected by,
and are made vulnerable to, diseases and related healthrisks.138 Women in particular tend to be more vulnerable
than men to disease outbreaks, including zoonoses(though COVID-19 may be an exception). In Liberia, forinstance, the government reported that 75 per cent of
epidemic victims were women, as they are more often
than not at the forefront of human-animal interactions.139

Section IV | Managing and preventing zoonoses: How One Health can help

41

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

One Health approach—What can we learn from past zoonotic disease outbreaks?

Chickens sold at the Ganeshguru livestock market, Guwahati, India
Photo credit: ILRI/Stevie Mann

Given that COVID-19 is only one of a series of emerging zoonoses, the experiences of the past can inform
strategies for the future. Overall efforts to strengthen systems for prevention, detection and responseto emerging infectious diseases in Asia have had mixed results. Significant investment has been madeby development partners and developing countries following the epidemic of highly pathogenic avian
influenza virus of type A and subtype H5N1 (HPAI [H5N1]) in 2004. Surveillance and diagnostic capacity havebeen built but HPAI remains endemic in key countries across much of Southeast Asia and in Egypt. Efforts
to strengthen capacity in Africa to detect and manage pandemic threats have only just started and services
lag behind Asia. The One Health approach has been advocated by many, but its uptake and institutional
support is uneven. More investment and support is required before such approaches can be implemented
routinely. In addition, a standardized set of metrics to measure the effectiveness of One Health interventions
may also help to increase uptake of the approach.140

Recognizing the instrumental role women could play incontrolling disease outbreaks, there has been a series
of “Women and One Health Workshops” highlighting
the pressing need for a more inclusive and gendersensitive approach to One Health policies, particularly ina developing-country context.139 These workshops aim tobuild a foundation for effective policies addressing genderinequalities that so often underlie zoonotic-diseaserelated risk factors.
While few would argue against setting up programmes to
respond to zoonotic outbreaks, there are concerns that,first, our responses may end up costing more than the
diseases themselves, and, second, that these costs may beborne disproportionately by the world’s poorest people.
During the bird flu pandemic, which started in 1997, there
were several attempts to “restructure” the poultry industry,
which in effect meant discouraging poor “backyard”
poultry farmers, many of whom were women with few
other ways to generate an income.141 And a recent studyin Egypt found that large-scale culling of poultry in
response to an outbreak of bird flu (HPAI) was associatedwith an increase in childhood malnutrition.142 Likewise,bans on wildlife trade, while sometimes successful, havein other cases led to unintended consequences, suchas when a ban on polar bear products impoverishedlivelihoods in indigenous Arctic communities and reduced
the communities’ tolerance for polar bears near theircommunities and participation in shared management

42

initiatives.143 Response measures inappropriately targeting
wildlife—such as poisoning or depopulation efforts—
may threaten biodiversity and ecosystem services. Theselessons reinforce the notion that interventions must
weigh possible benefits with potential trade-offs; such an
approach can help to optimize resource use and ensure
equitable solutions.

Lessons from managing previous
coronavirus outbreaks
Because we are in the midst of an ongoing pandemic, itwill require some time before clear conclusions can be
drawn on the best ways to manage COVID-19. Already,we can see the need for rapid learning, uptake of goodpractices such as real-time surveillance data, and global
solidarity around resources. However, lessons learned fromprevious coronavirus epidemics and pandemics in animals
and people suggest the following.
Like all viruses, over time, coronaviruses mutate into newstrains possessing different degrees of pathogenicity(the ability to invade and cause disease within the host),
virulence (severity of the disease in infected hosts)
and infectiousness (capability of being transmitted).
Coronaviruses have a slower mutation rate than someother RNA viruses, which means that once an effective
vaccine is produced, it will likely provide protection
against the virus for much longer than, say, that provided
by today’s annual influenza vaccines.

Section IV | Managing and preventing zoonoses: How One Health can help

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

It has been difficult, however, to develop effective vaccines
against livestock coronavirus-caused diseases of higheconomic cost. Because outbreaks of novel coronavirus
diseases occur fairly regularly—as noted, six recent global
coronavirus outbreaks have all spread widely, affecting
several continents—coronaviruses should have higher
priority among the viruses that need study and surveillance.

Video: WAHIS: Protecting animals,preserving our futureVideo Link: https://www.youtube.com/watch?v=M5PuNtcBh14 |© OIEVideo

Previous coronavirus outbreaks have entailed enormous
financial costs and social disruption. The human healthburden of zoonotic coronaviruses has been relatively low,
but with the potential to be much higher. Risk assessment,
mitigation and communication must be improved. Andin many countries, most of the direct and indirect burdenof disease control has fallen on the poorest, indicatinga pressing need to provide people with better social
protection and increased resilience to disease.
Compared with the SARS epidemic, both the scientificand public health responses to COVID-19 have beencommunicated differently, but incentives for countries
to declare outbreaks early remain weak, especially indeveloping and emerging economies. That needs tochange in order to facilitate both global readiness andeffective international collaboration.
The economic impacts of COVID-19 by June 2020 appear
to be many times worse than those of previous known
coronavirus outbreaks. The economic losses linked to an
outbreak include both direct and indirect losses. When
pandemics have a relatively low population mortality rate
(perhaps much less than 10 per cent as appears to be thecase of COVID-19), the indirect costs of the pandemic tend
to be much higher than the direct costs. These indirect
costs include loss of jobs, disrupted food supply chains,border closings, restricted mobility, restricted tourism,
reduced education opportunities, business closures/bankruptcies, a rise in fatalities because health services
Exposure
in animals
Clinical signs
in animals

Exposure Clinicalin
signs
humansinhumansCost ofcontrol
outbreak

Humans seek
medical care

Effective control of zoonotic diseases requires early detection andaccurate diagnosis at the animal source. Disease surveillance inanimals is critical for preventing the spread of disease between
animal populations, and minimizing the risk of transmission
to human populations. The cost of disease control increases
exponentially once the disease spreads among humans.10
Source: World Bank (2012)

MONITORING SYSTEM
are overwhelmed or people avoid them, and manyother complex downstream effects. Many ongoing andproposed actions are addressing these costs but they are
not within the remit of this paper.
Control of coronavirus and other zoonotic infections infarmed domestic animals, farmed and captured wildlife
and companion animals is difficult in all countries andperhaps impossible in many developing countries. The
best veterinary practice requires combined applicationsof vaccines, biosecurity protocols, movement controls andhusbandry management, all of which are very difficult toimplement in poorer countries. Because vaccines used for
porcine epidemic diarrhoea are not always effective, strict
biosecurity is the most effective measure to prevent the
introduction and spread of the virus. This has almost neverbeen successfully applied to smallholder farms supplying
mass domestic markets. Vaccines are also unsatisfactoryin preventing infectious bronchitis in chickens andfeline infectious peritonitis. Infectious bronchitis andporcine epidemic diarrhoea have been better controlled
in Europe than in China but remain global pandemics.
Coronaviruses that are well-adapted to their hosts are
difficult to eradicate.
While SARS appears to be eliminated, MERS continues tocause human deaths, because the virus still circulates in
the intermediate host (dromedary camels). Vaccines were
initiated for SARS but did not progress beyond phase-one
human trials. Vaccines are currently under development
for MERS but not yet approved. A race is now on among
the large private pharmaceutical companies, academic
units and small biotech companies to develop a vaccine
for COVID-19. More than one hundred companies are
involved in this work, but there remain real challenges,
not only to developing an effective vaccine for this novel
coronavirus, but also for quickly mass-producing it insufficient quantities, and ensuring that it is available toall regardless of income, to protect every one of the
7.8 billion people living today on planet Earth.

Section IV | Managing and preventing zoonoses: How One Health can help

43

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

44

Section V | Preventing future zoonotic pandemics: What more could be done?

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Section Five

Preventing future zoonotic pandemics:
What more could be done?
This final section looks at additional policy and practiceresponses that can help prevent the inevitable next
emerging zoonosis to appear on the horizon. Again, it
focuses on the One Health approach as the preferredframework for zoonoses risk reduction and control anddiscusses how this could add value to attempts to mitigate
the seven anthropogenic drivers of zoonoses emergenceidentified in Section One. It makes ten concrete, OneHealth-based recommendations that could address theunderlying causes, while also supporting a more effective,
coordinated response to future pandemics.

One Health aspects of zoonoses control andprevention
Controlling and preventing zoonotic outbreaks requires
coordinated interdisciplinary responses across human,
animal and environment health. Our responses to bothcontrolling the ongoing COVID-19 pandemic and to
reducing the risk of future zoonotic disease outbreaks must
address a range of areas.
In the immediate crisis, a public health response must be
mounted, financed and managed. Maintaining the global
food system is a top priority, as is providing additionalsocial protection for poor, vulnerable and marginalized
populations. A clear exit strategy from pandemic responses
is needed, as are sustainable ways of re-building damaged
economies while not sacrificing long-term social andenvironmental achievements. There are many reports,
guidelines and suggestions addressing these issues. This
report, and this section in particular, takes a broader viewand recommends ways to prevent and mitigate the risks
posed by zoonotic diseases, with a particular focus onanimal and environment health aspects. It will be critical toincorporate these aspects in short-term recovery packages,
as well as in longer-term policy and development planning.

traditional sectoral barriers to achieve effective control ofzoonoses. A promising development in the wake of thebird flu pandemic is the establishment of joint zoonoses
working groups in many countries and other international
collaborations.145
Successful control of zoonoses requires strong policy
frameworks and judicious legal mechanisms toaccompany policy frameworks. It also demands wellfunctioning institutions that have adequate capacity,
adequate financing and a clear plan for implementing
interventions.
In the case of emerging diseases, up-front investments
in surveillance and in coordinated human, animal andenvironment health services are needed to ensure that‘emergence events’ do not turn into full-scale epidemics,
or pandemics. In economic terms, the World Bank
estimated eight years ago that an annual investment of
USD3.4 billion in animal health systems worldwide would
avert losses incurred through delayed or inadequate
responses to zoonoses—losses estimated at almost
double the preventative investment.10 The loss of human
life, and economic and social costs of the COVID-19
crisis clearly indicate the value—and the necessity—of increased investment in surveillance, prevention
measures and coordinated cross-sectoral early response
to ensure we do everything possible to prevent this fromhappening again.
Video: What is One Health?
Video Link: https://www.youtube.com/watch?v=kfluP-tFC2k |© Simpleshow foundation

As noted, zoonoses are complex; responsibility for theirprevention and control falls across several sectors—
environment, agriculture, health, trade and commerce.
Approaches to dealing with these diseases to date havebeen inadequately coordinated across these multiple
dimensions.144 Institutionally speaking, zoonoses can findthemselves outside conventional health fields (falling
between different siloed sectors of human and veterinary
health) and, in the worst cases, ignored. One Healththinking and research offers an approach to break down

Section V | Preventing future zoonotic pandemics: What more could be done?

45

VPreventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Improved interdisciplinary science will help to informthe prevention and control of zoonotic diseases. It is
important not to study pathogens in isolation, but rather
to better understand how human social behaviour
impacts the natural world, as well as the emergence andspread of disease.146 These relations are non-linear andinvolve complex systemic relationships that must be
factored into both research and effective decision-making.

diseases are still reactive rather than proactive. During
any disease crisis, much effort is spent in developing
immediate responses. However, much less investment
is made in building communities’ resilience to future
outbreaks and, even more importantly, in addressing theunderlying structural problems or drivers that are causing
the recurrence of animal and human epidemics andpandemics.

Success will require addressing the root causes anddrivers of disease emergence, which in turn will requirechanging our behaviour and our actions in relation to
ecosystems. While some of the basic ecological factorsof disease emergence are known, these factors need to
be integrated fully into country-level surveillance andresponse programmes with relevant expertise included ininter-sectoral teams.

Our present crisis in 2020 provides us with an opportunity
to “build back better.” Collectively, we need to shift fromshort-term political responses to long-term politicalcommitments to secure human, animal and environment
health. Sustaining all life on Earth depends on it.

Many zoonotic diseases can occur along with otherinfectious diseases within a given environment or
host.147 This can complicate disease management if eachpathogen requires a different measure to control it. It isalso critical to understand these interactions and identify
opportunities to control multiple pathogens or vectors
with a single intervention.

Addressing the anthropogenic drivers ofzoonoses emergence
A major constraint to moving towards a pandemicfree world is that most efforts to control infectious

Many of these seven drivers have shared underlying
causes. For example, the growing demand for foodcan cause agricultural systems to intensify, and pay
insufficient attention to important consequences related
to environmental and human health,148 changes to foodvalue chains, and increased utilization of wildlife.
The COVID-19 crisis has highlighted vulnerabilities
in the current global food system. These range fromstrains on local, regional and global supply chainsdue to “lockdowns,” to very specific problems, such as
disruption in crop production that have occurred due tointerruptions in the transport of commercial beehives
to supply critical pollination services.149 Many local foodmarkets have been forced to close because of perceived
high risks of COVID-19 due to the density of people andCommuters wearing masks during the COVID-19 pandemic in Bangkok, Thailand
Photo credit: The Escape of Malee / Shutterstock.com

46

Section V | Preventing future zoonotic pandemics: What more could be done?

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

animal products and low abilities to enforce hygiene andsocial distancing measures. These market closures haveincreased food insecurity, according to the International
Panel of Experts on Sustainable Food Systems (April 2020).
Increased support is necessary to build resilient
agroecological food systems that rely on natural synergies
and harness biological diversity for food production while
protecting important wildlife habitats. This is needed not
only to decrease the risks of potential zoonotic outbreaks
but also to build resilience in human communities towithstand the impacts of zoonotic outbreaks. Investments
in local supply chains, including strengthening local
abilities to meet food safety regulations, are also part of
the necessary transformation to sustainable food systems.
Lastly, a farm-to-fork approach must be taken with regards
to reducing risk from zoonotic diseases along the entire
consumptive chain, from production to processing, andtransport to consumption of food. Many of these issues
are examined in more depth later in this section.

Strengthening the environment
dimensions of the One Health approach
All seven anthropogenic drivers of zoonotic disease listed
above have a strong environmental dimension. However,environmental science, scientists and practitioners aswell as environmental policies have been inadequately
incorporated in the One Health approach, whileenvironmental considerations have been insufficiently
mainstreamed in its development and implementation.
These oversights have significantly limited the success of
the One Health approach to date.3
Moving forward, we must further invest in understanding
the underlying environmental links with infectious
zoonotic diseases and the emergence of those diseases.
We must work to monitor zoonotic disease in humandominated environments (where live animals may besold), in areas where human settlements are encroachingon wildlife habitats, as well as in intact ecosystems thatare home to important wildlife species. Such work will
help us to establish essential baselines. We also need toinvestigate how the transformation and degradation of
habitats—whether due to urbanization, risk-averse firepolicies, inappropriate agriculture or other development,
restoration or re-wilding of areas, or other forms ofenvironmental change and degradation—are affecting
the emergence of diseases. A deeper understanding of
how existing stressors, including pollution and climatechange, exacerbate risks and impacts from zoonotic
disease is also warranted. In particular, we must further
strengthen research capacity-building, and further
investigate the links between wildlife exploitation,
zoonotic disease emergence, and the potential risk of an
epidemic or pandemic.

Video: Controlling zoonotic diseases through a
One Health approach preserving our futureVideo Link: https://youtu.be/RL0izxaUoMk | © ILRI

A farmer and her pigs in Tete province, Mozambique
Photo credit: ILRI/Stevie Mann

An example of studying the complex relationshipbetween biodiversity and infectious disease outbreaks isprovided by the Great Apes Survival Partnership (GRASP)
programme. Working with conservation partners andthrough implementation at the level of local communities,
for instance, this programme developed protocols tomonitor human and wildlife health in the Republic ofCongo. Results from this project led to recommendations
for African great ape range states.150 This technicalapproach could be replicated in other regions to monitor
the outbreak and spread of human and wildlife diseases atdifferent stages of habitat alteration and identify hotspots
where interventions aiming to reverse or halt natural andbiodiversity losses are required.

Leveraging innovations and newtechnologies
Without more fundamental knowledge of pathogen
epidemiology and more rapid and inexpensive
genome sequencing, every new serious emerging
disease will continue to take us by surprise. However,additional investments in new technologies, particularly
biotechnologies and information and communication
technologies, could stimulate the innovation of “gamechangers” in disease surveillance, rapid response andcontrol.
Specific improvements in biosecurity are critical for
detecting, preventing and controlling zoonotic disease
outbreaks, and for implementing rapid and adequate
emergency responses. These include preventive measuresdesigned to reduce risk of infectious disease transmission
in crops, livestock, quarantined pests, invasive alien
species and living modified organisms. While several
studies found that biosecurity advice and policy are often
sound, there is limited implementation of biosecurity

Section V | Preventing future zoonotic pandemics: What more could be done?

47

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Effective policy responses to mitigate threats fromzoonotic diseases require concerted policy action to stem
the multiple drivers of their emergence, which include
habitat loss and degradation, overexploitation of wildlife,and land-use changes, among other factors. This will
be particularly important in cases where fragmented
habitats are thought to play a role in stimulating rapid
evolutionary processes and diversification of diseases.
These land-use change and habitat-associated policy
responses must be considered in the context of potential
climate change risks. This is especially important for any
policies aiming to mitigate risk from pathogens thatspend part of their life cycle outside of their hosts, as is
the case for vector-borne diseases, which have proven to
be more climate sensitive.157

Video: FAO: Changing disease landscapes Towards a Global Health approach
Video Link: https://www.youtube.com/watch?v=vHVSW5HwmZM |© FAO

measures, especially among small-scale livestock keepers,
due to a lack of resources and incentives.
Some impediments to implementing biosecurity
interventions include a lack of awareness in farmersof the risk and the cost and convenience of protective
measures.151,152 A study in Uganda found that even thoughimplementing biosecurity practices would reduce losses
from African swine fever, it would also reduce farmer profit
margins by 6 per cent per year.153 We need new approaches
that rely more on incentives, systemic understanding, andequitable sharing of risk.
However, while innovation is key to pandemic solutions,improved biosecurity is also needed in laboratories that
research emerging infectious diseases. While there isno evidence that this played any role in the COVID-19
pandemic, there are many documented incidences oflaboratory-acquired infections and even accidental escapesof highly pathogenic organisms from laboratories.154,155

Transforming and re-governing foodsystems
Preventing future zoonotic disease outbreaks also
requires improvements in policy, regulation andmonitoring of traditional food markets. Millions of people
depend on informal food markets that occur in public
spaces where small-scale retailers come together to sell
fresh produce, fish and meat from domesticated animals,
and in some cases, from wild animals. While many recent
zoonotic pandemics originated in wildlife,158 a similarly
large number originated in livestock. To reduce risks
of future zoonotic diseases, meat from both wild anddomesticated origin—and the places in which the meatis sold—should be subject to similarly strict sanitary
standards.

Responding to public and policy demand forthe prevention and control of zoonoses
While further research and innovation are critical, a numberof effective strategies to control neglected zoonoses
have already been identified. A main barrier to the wide
uptake of these strategies is a lack of investment in disease
control, particularly in developing countries. The costs of
preventing or controlling a zoonotic disease can seem highwhen compared to the direct public health benefits of suchactions.
However, the costs of prevention are easily outweighedby the benefits. This becomes evident when a full analysisof the social, economic and ecological consequences of apotential outbreak across multiple sectors is undertaken,
including losses of livestock, wildlife, tourism, forestry,
trade, employment and other areas.156 COVID-19 has madethis clear.

48

Dissecting infected ticks in ILRI’s Tick Laboratory
Photo credit: © ILRI / David White

Section V | Preventing future zoonotic pandemics: What more could be done?

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

A

90
80

Domestic animal
amplification

Vectors

Number of cases

70

Spillover60
Wild animal cases
Domestic animal cases
Human cases

50
40
30

SpilloverSpilloverHumanamplification

20
10
0

B

Control benefits
to animals

Forecastingreadiness

80

Control benefits
to people

70
Number of cases

Rapid response

Early
detection

90

Control
operations

60

Wild animal cases
Domestic animal cases
Human cases

50
40
30
20
10
0

0

7

14

21

28

35

42

49

56

63

70

77

84

Time (days)
Clinical relevance of disease ecology(A) Transmission of infection and amplification in people (bright red) occurs after a pathogen from wild animals (pink) moves into livestock tocause an outbreak (light green) that amplifies the capacity for pathogen transmission to people. (B) Early detection and control efforts reduce
disease incidence in people (light blue) and animals (dark green). Spillover arrows shows cross-species transmission.167
Source: Reprinted from The Lancet, Vol.380, Karesh et al., Ecology of zoonoses: natural and unnatural histories, Page 1942, Copyright (2012), with permission from Elsevier.

Furthermore, strengthened sanitary regulations must
go beyond public food markets and include the entire
supply chain for domesticated and wild meat, including
both farmed and captured wildlife. Better enforcement ofthese standards is absolutely essential to reduce risk. WHO
has developed guidelines for healthy food markets.159
Adoption of animal welfare standards for the care, housing
and transport of live animals along the entire supply

chain is also needed to reduce risk of zoonotic diseasetransmission.160 Additional restrictions on which species
can be legally sold should also be considered, as is being
done in Asia in the wake of the COVID-19 crisis. Additional
options for reducing risk, including bans on the highestrisk markets, must also be considered if there is evidence
that such measures would be effective in preventing
future pandemics.

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Preventing the next pandemic:
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Any consideration of additional regulations on
informal markets, including those involving legallyconsumed wild meat, must consider social equity
and human vulnerability. Some populations may bedisproportionately dependent on these sources of protein
to meet their food security needs.

Sustainable use of wild resources andMultilateral Environmental Agreements
Sustainable use of biodiversity or wild natural resources—a critical component of the Convention on Biological
Diversity (CBD)—includes non-consumptive uses ofwildlife, such as sustainable tourism and wildlife viewing,as well as consumptive uses. Consumption, handling andtrading of wildlife—including for food, pets, zoos andmedical research—can be a factor in the transmission of
zoonotic diseases.
The Convention on Migratory Species (CMS) addresses
the conservation and management of migratory species
that are endangered or whose conservation status isunfavourable, and the taking and use of such species. It
established an expert group on wildlife diseases in 2005.
Sustainable use is central to the economic and social
sustainability of wildlife and its habitats. The Convention
on International Trade in Endangered Species of Wild
Fauna and Flora (CITES) has established a non-detrimentfinding mechanism to ensure that international trade inwildlife is biologically sustainable. Additional measures

to ensure safety for human health components as partof trade regulations, and improved application of allthese measures at national levels, would benefit zoonotic
disease control.
Demand management for consumption of wildlife, andassociated policies to incentivize such shifts in demand,
have been indicated as a possible and appropriate
response to reduce zoonotic risk. Demand management
interventions are most successful when they are based ona clear understanding of the social, economic and cultural
aspects of wild meat consumption along the entire value
chain, from producer (or hunter) to consumer.107 Demand
management measures should be put in place as part of acomprehensive package of policies and interventions that
address all aspects of human, animal and environment
health. The human and animal dimensions of healthinclude disease transmission aspects but also nutrition,
welfare and food security components. In cases where
human nutrition and livelihoods are dependent on the
consumption and/or trade in wild meat or live animals,
careful consideration must be given to viable alternatives,
particularly for poor or marginalized people. This becomeseven more critical when bans of wild meat or live animal
marketing are being considered. Expansion of diversified
income sources is often an essential component to shift
incentives along the wild meat supply chain to groweconomic resilience and ensure continued incentives forwildlife conservation. Diversification should be based ona thorough understanding of the dynamics of the system

A villager and her sheep in Fakara, Niger
Photo credit: ILRI / Stevie Mann

50

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Preventing the next pandemic:
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Commuters at Shinagawa train station in Tokyo, Japan
Photo credit: StreetVJ / Shutterstockand clear business planning for alternative means ofgenerating income.170,171
The Collaborative Partnership on Sustainable Wildlife
Management describes some of the key factors to ensuresustainability of wild meat consumption, including
careful monitoring of animal populations, strengthened
tenure and management rights for local populations,and provision of technical expertise to support the
management of animal populations as well as toimplement stringent sanitary measures for the sale,transport and consumption of wild animals and meat.
Management measures, such as temporary bans to allow
wildlife population recovery as well as removal of nonproductive animals, may also be effective.

Interventions at the human-livestock
interface
Many zoonoses can be best tackled through interventions
involving the livestock hosts of the disease pathogens.172
Improved and sustained collaboration between medical,
veterinary and wildlife authorities is necessary to improve
surveillance and control of zoonotic diseases. Whilethese authorities may come together during a crisis tocollaborate and share resources, as is the case now where
many veterinary laboratories are supporting testing forthe current novel coronavirus, these collaborations are
not fully institutionalized and often discontinue in noncrises periods. Intensive livestock production systems
would benefit from stringent biosecurity and veterinary
control measures. Extensive livestock production systems,
including pastoralism, can provide proteins efficiently
while also providing environmental co-benefits andreduced zoonotic disease risk. The control of coronavirus
and other zoonotic infections in farmed domestic animals,
captured wild animals and companion animals is difficult

in many developing countries. This generally requires
combined applications of vaccines, biosecurity protocols,
movement controls, slaughter of affected animals andquarantine of premises, and husbandry management,
among other measures.

Towards evidence-informed policy
A stronger evidence base and greater capacity-building
is needed to understand complex risk profiles and toassess the costs, benefits, acceptability and scalability ofsuch interventions. In addition, many interventions tocurb zoonotic disease in animals that were promising in a
project context have not been taken up by development
programmes or the public sector. For example, a review ofdifferent ecosystem and animal interventions to control
sleeping sickness in five African countries found they
worked well during the project, but that the disease reemerged after the project ended.164 Future efforts mustensure that proven preventive measures that mitigate
zoonotic disease transmission among livestock areincorporated in policy frameworks. Disease discriminates,with the burden of neglected zoonotic diseases fallingheaviest on poor, vulnerable and marginalized people.165
To be effective, zoonoses control programmes must findways to reduce the barriers that disadvantaged groups
face in managing diseases in the animals they keep, andin accessing disease control services for themselves andtheir animals.
Key actors in implementing the recommendations of
this report include research institutions, national andlocal governments, intergovernmental organisations,non-governmental organisations and businesses. A
clear interdisciplinary research agenda on zoonotic
diseases has been described. The aim of this agenda is
not only to improve understanding of the human, animal

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Preventing the next pandemic:
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Seafood at a fish market
Photo credit: Vladimir Krupenkin / Shutterstock.com

and environmental dimensions of health, but also to
pursue applied research on the socio-economic policy
dimensions of addressing these factors in integrated
ways. While many One Health approaches are employed
by interdisciplinary teams at national levels, it isimportant that the approaches are fully employed at local
governance levels using the best available science.
Non-governmental organisations provide critical technicalassistance and multidisciplinary support in rolling out One
Health approaches. Intergovernmental organisations havean important role in the coordination of the response to
global pandemic threats, including collating information,
providing guidelines and advice, developing response
strategies and sharing lessons learned for improved
preventive actions. WHO works in close collaboration with
FAO and OIE to promote cross-sectoral collaboration toaddress risks from zoonoses and other public health threatsat the human-animal-ecosystem interface, and to provide
guidance on how to reduce these risks. UNEP, the sciencebased global environmental authority of the United Nations,and the Secretariats of the Multilateral Environmental
Agreements (MEAs) that it administers, have a clear roleto play in expanding the environmental dimensions of
this approach, including strengthening environmental
laws and their enforcement. Several examples of possible
entry points have been identified in voluntary guidance on
biodiversity-inclusive One Health approaches.

52

The World Bank recently issued guidelines for
operationalizing One Health in existing and future
projects undertaken by the Bank and its client countries
and technical partners.166 These guidelines can serve asa model for other financial institutions to incorporate inplanning processes for development and infrastructure
projects. Furthermore, the business sector must assess its
investments, incentive structures and business practices
to understand the material risks of creating zoonotic
pathogen spillovers.
For example, reformed risk assessments that incorporate
potential hazards from zoonotic spillovers and diminishedforest-associated health benefits can be combined withsustainability commitments as part of up-front financing
for forest-converting commodities, such as soy or palm oil.
Greater efforts must be made to raise awareness among
politicians, particularly with regards to the importanceof investing in interdisciplinary surveillance, detection
and preventive measures. The current crisis clearly
demonstrates the much greater cost of not investingin detection, prevention and early response. However,curbing zoonotic disease outbreaks and their impacts
does not stop with national decision-makers, but requires
increased awareness-raising of risks and proactive
mitigation steps at the level of communities, farmers, andindividual consumers of animal and other food products.

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Ten key policy recommendations
As of June 2020, most papers and guidelines that discuss
policies and actions to tackle the novel SARS-CoV-2 virus
and COVID-19 pandemic focus on how to prevent andtreat the disease, or how to safeguard livelihoods, secure
nutrition and re-build national and regional economies.
This paper focuses on recommendations based on the
One Health approach. The recommendations set forth
here can help governments, businesses and other actors
not only to respond to and mitigate future disease
outbreaks, but also to reduce the risk of their emergence.
To this end, the following ten science-based policy
recommendations are proposed:
1.

AWARENESS: Raise awareness and increase
understanding (knowledge) of zoonotic andemerging disease risks and prevention (whereappropriate), at all levels of society to build
widespread support for risk-reduction strategies.

2.

GOVERNANCE: Increase investments ininterdisciplinary approaches including the One
Health perspective; strengthen the integrationof environmental considerations in the World
Health Organization (WHO)/Food and Agriculture
Organization (FAO)/World Organisation for Animal
Health (OIE) Tripartite Collaboration.

3.

SCIENCE: Expand scientific enquiry into the complex
social, economic and ecological dimensions ofemerging diseases, including zoonoses, to assess
risks and develop interventions at the interface of theenvironment, animal health and human health.

4.

FINANCE: Improve cost-benefit analyses of emerging
diseases prevention interventions to include fullcost accounting of societal impacts of disease(including the cost of unintended consequencesof interventions) so as to optimize investments
and reduce trade-offs. Ensure ongoing and wellresourced preparedness and response mechanisms.

5.

MONITORING AND REGULATION: Develop effectivemeans of monitoring and regulating practices
associated with zoonotic disease, including foodsystems from farm to fork (particularly for removing
structural drivers of emergence) and improving
sanitary measures, taking into account thenutritional, cultural and socio-economic benefits ofthese food systems.

6.

INCENTIVES: Include health considerations in
incentives for (sustainable) food systems, including
wildlife source foods. Augment and incentivize
management practices to control unsustainableagricultural practice, wildlife consumption and trade(including illegal activities). Develop alternatives
for food security and livelihoods that do not rely on
the destruction and unsustainable exploitation of
habitats and biodiversity.
7.

BIOSECURITY AND CONTROL: Identify key driversof emerging diseases in animal husbandry, bothin industrialized agriculture (intensive husbandrysystems) and smallholder production. Include properaccounting of biosecurity measures in productiondriven animal husbandry/livestock production tothe overall cost of One Health. Incentivize provenand under-used animal husbandry management,
biosecurity and zoonotic disease control measures
for industrial and disadvantaged smallholder farmers
and herders (e.g. through the removal of subsidies
and perverse incentives of industrialized agriculture),and develop practices that strengthen the health,opportunity and sustainability of diverse smallholder
systems.

8.

AGRICULTURE AND WILDLIFE HABITATS: Support
integrated management of landscapes and seascapesthat enhance sustainable co-existence of agriculture
and wildlife, including through investment in agroecological methods of food production that mitigate
waste and pollution while reducing risk of zoonotic
disease transmission. Reduce further destruction andfragmentation of wildlife habitat by strengthening
the implementation of existing commitmentson habitat conservation and restoration, themaintenance of ecological connectivity, reductionof habitat loss, and incorporating biodiversity values
in governmental and private sector decision-making
and planning processes.

9.

CAPACITY BUILDING: Strengthen existing andbuild new capacities among health stakeholders inall countries to improve outcomes and to help themunderstand the human, animal and environment
health dimensions of zoonotic and other diseases.

10. OPERATIONALIZING THE ONE HEALTH APPROACH:
Adequately mainstream and implement the One
Health approach in land-use and sustainable
development planning, implementation andmonitoring, among other fields.

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in our understanding of impacts on ecosystems. Journal of Medical Entomology, 56(6), 1491–1497. https://doi.org/10.1093/jme/tjz149

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Byas, A.D. and Ebel, G.D. (2020). Comparative pathology of West Nile virus in humans and non-human animals. Pathogens, 9(48). https://doi.
org/10.3390/pathogens9010048

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Loh, E.H., Murray, K.A., Nava, A., Aguirre, A.A. and Daszak, P. (2016). Evaluating the links between biodiversity, land-use change, and infectious
disease emergence in tropical fragmented landscapes. In Tropical Conservation: Perspectives on Local and Global Priorities. Aguirre, A.A. and
Sukumar, R. (eds.). Oxford University Press, New York City.

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Grace, D. (2015). Food safety in low and middle income countries. International Journal of Environmental Research and Public Health, 12, 10490–
10507. https://doi.org/10.3390/ijerph120910490

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Rohr, J.R., Barrett, C. B., Civitello, D. J., Craft, M. E., Delius, B., DeLeo, G. et al. (2019). Emerging human infectious diseases and the links to global
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Graphic References

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Preventing the next pandemic:
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Glossary
Aerosol transmission: One of two airborne meansof infectious disease spreading. In aerosol form, viralparticles are suspended in the air by physical and chemical
forces for hours or more. In droplet form, in contrast,
viral particles remain airborne for a few seconds after
someone sneezes or coughs and are able to travel only ashort distance before gravitational forces pull them down.
STAT News
African trypanosomosis (also spelled ‘trypanosomiasis’):A disease of livestock (‘African animal trypanosomosis’)and humans (‘sleeping sickness’). These diseases
are caused by single-celled trypanosome parasites(Trypanosoma brucei gambiense, Trypanosoma rhodesiense
and Trypanosoma brucei brucei) that are transmitted totheir animal and human hosts by the bite of trypanosomeinfected tsetse flies (genus Glossina), which are found only
in Africa. US CDC
Agricultural intensification: An increase in agricultural
production per unit of inputs (e.g. labour, land, time,
fertilizer, seed, feed, cash). This intensification has been aprerequisite to human civilization. Increased production
is critical for expanding food supply; intensification thatmakes efficient use of inputs is critical for maintaining thehealth of agricultural environments. FAO
Anthrax: An ancient zoonotic disease that continues tocause serious illness in livestock, where it is a particularthreat to cattle and small ruminants like sheep and goats.
It can affect all warm-blooded animals, including humans.
Treatment is possible with early diagnosis but often there
are no symptoms and infected animals die swiftly. Humans
generally acquire the disease directly or indirectly from
infected animals or occupational exposure to infected orcontaminated animal products. Although many countries
have confirmed cases, this is not, in the main, a disease of
wealthy countries. Incidences of both animal and humananthrax are frequently associated with conflict. FAO
Anthropogenic: Caused by humans or their activities.
Cambridge Dictionary
Arthropod: An invertebrate animal having
an exoskeleton, a segmented body and paired
jointed appendages. Arthropods include insects, arachnids(such as ticks and spiders), myriapods and crustaceans.
Biologydictionary.net

64

Asymptomatic carriers, also known as ‘passive’ or‘healthy’ disease carriers: Individuals that, while infectedwith a pathogen, neither report nor appear to have any
symptoms or signs of illness. US CDC
Avian influenza: A severe, often fatal, type of influenzathat affects birds, especially poultry, and that can also
be transmitted to humans. Known informally as avian
flu or bird flu, the type with the greatest risk is highly
pathogenic avian influenza (HPAI). Of three types ofinfluenza viruses (A, B and C), influenza A virus isa zoonotic infection with a natural reservoir almost
entirely in birds. Avian influenza, for most purposes, refers
to the influenza A virus. Though influenza A is adapted
to birds, it can also stably adapt and sustain person-toperson transmission. WHO
Behavioural nudging: In behavioural sciences, it is
proposed that positive reinforcement and indirectsuggestions can influence the behaviour and decisionmaking of groups or individuals. Nudging contrasts withother ways to achieve compliance, such as education,
legislation or enforcement.
UK ESRC and Wikipedia
Biodiversity: The variability among living organisms
from all sources, including terrestrial, marine and otheraquatic ecosystems, as well as the ecological complexes ofwhich they are part. Biodiversity includes diversity within
species, between species and of ecosystems. CBD
Biosecurity: A series of measures aimed at preventing
the introduction and/or spread of harmful organisms inorder to manage the risk to people, animals, plants andthe environment. Biosecurity covers issues such as theintroduction of plant pests, animal pests and diseases,
and zoonoses, the introduction and release of geneticallymodified organisms and their products, and theintroduction and management of invasive alien species
and genotypes. The COVID-19 pandemic is a recent
example of a threat that requires biosecurity policies andregulatory measures in all relevant sectors. FAO
Biotechnology: Any technique that encompasses a mix
of scientific and practical disciplines and employs livingorganisms, or parts of such organisms, to make or modify
products, to improve plants or animals or to develop
microorganisms for specific uses. Biotechnologicalmethods range from the traditional (beer- and breadmaking) to the most advanced (genetically modified

Glossary

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

plants and animals, cell therapies and nanotechnology).
World Bank
Bovine spongiform encephalopathy (BSE): Commonly
known as ‘mad cow disease’, BSE is a progressive, fatal
disease of the nervous system of cattle caused by theaccumulation of an abnormal protein called ‘prion’ in
nervous tissue. First detected in 1986, the implementationof appropriate control measures resulted in the decline ofclassical BSE cases worldwide. BSE is considered zoonotic
due to its assumed link with the emergence of variant
Creutzfeldt-Jakob disease in humans. OIE
Bovine tuberculosis: Zoonotic tuberculosis is a formof tuberculosis in people caused by Mycobacterium
bovis, which belongs to the M. tuberculosis complex.
It often affects sites other than the lungs, but in manycases is clinically indistinguishable from TB caused by M.
tuberculosis. Within animal populations, M. bovis is thecausative agent of bovine TB. It mainly affects cattle, which
are the most important animal reservoir, and can become
established in wildlife. The disease results in importanteconomic losses and trade barriers with a major impact
on the livelihoods of poor and marginalized communities.
WHO-OIE-FAO
Brucellosis: A bacterial infection that spreads fromanimals to people. Most commonly, people are
infected by eating raw or unpasteurized dairy products.
Sometimes, the bacteria that cause brucellosis canspread through the air or through direct contact with
infected animals. The infection can usually be treatedwith antibiotics but treatment takes several weeks tomonths, and the infection can recur. Brucellosis affects
hundreds of thousands of people and animals worldwide.
Mayo Clinic
Campylobacter bacteria: One of four key global causesof diarrhoeal diseases and considered the most common
bacterial cause of human gastroenteritis in the world.
Campylobacter are mainly spiral-shaped, ‘S’-shaped or
curved, rod-shaped bacteria. Campylobacter infections
are generally mild but can be fatal among very young
children and elderly and immunosuppressed individuals.
In developing countries, Campylobacter infections inchildren under the age of 2 years are especially frequent,sometimes resulting in death. Campylobacter species canbe killed by heat and thoroughly cooking food. WHO
Chagas disease, also known as American
trypanosomiasis: A potentially life-threatening
neglected tropical disease caused by the protozoan
parasite Trypanosoma cruzi. Found mainly in Latin
American countries, where it is mostly vector-borne,
often by a ‘kissing bug’, an estimated 8 million people
are infected worldwide, mostly in Latin America. Chagas

Glossary

disease is clinically curable if treatment is initiated at an
early stage. The disease has spread to other continents
over the last century mainly because of greater travel. It
is estimated that over 10,000 people die every year fromclinical manifestations of Chagas disease and more than
25 million people risk acquiring the disease. WHO
Co-morbidities: More than one disease/condition present
in an individual at the same time. Other names to describe
co-morbid conditions are ‘co-existing’ or ‘co-occurring’conditions and ‘multimorbidity’ or ‘multiple chronic
conditions’. US CDC
Coronavirus disease 2019: Illness caused by a novel
coronavirus, ‘severe acute respiratory syndrome
coronavirus 2’ (SARS-CoV-2), which was first identified
amid an outbreak of respiratory illness cases in East Asia.
The outbreak was first reported to WHO on 31 December
2019. On 30 January 2020, WHO declared the COVID-19
outbreak a global health emergency and the following
March a global pandemic, WHO’s first such designation
since declaring H1N1 influenza a pandemic in 2009.
Medscape
Coronavirus OC43: Human coronaviruses (named for thecrown-like spikes on their surface) were first identified in
the mid-1960s. Seven coronaviruses can infect people.
Four of these are common human coronaviruses, 229E,
NL63, OC43 and HKU1, which usually cause mild tomoderate upper-respiratory tract illnesses like thecommon cold. But three of the seven coronaviruses—
MERS-Cov, SARS-CoV and SARS-CoV-2—are novel andlethal coronaviruses that originated in animals andevolved in ways that, in humans, can cause serious illness
and death. US CDC
Crimean Congo haemorrhagic fever (CCHF): A viralhaemorrhagic fever usually transmitted by ticks. It canalso be contracted through contact with animal tissue
where the virus has entered the bloodstream during and
immediately post-slaughter of animals. Outbreaks of thedisease can lead to epidemics, have a high case fatality
ratio (10–40 per cent) and are difficult to prevent andtreat. First described in the Crimea in 1944, the disease isendemic in all of Africa, the Balkans, the Middle East and in
Asia. WHO
Cysticercosis: A parasitic tissue infection caused by larval
cysts of the tapeworm Taenia solium. These larval cysts
infect brain, muscle or other tissue and are a major causeof adult onset seizures in most low-income countries. A
person gets cysticercosis by swallowing eggs found in
the faeces of a person who has an intestinal tapeworm.
People do not get cysticercosis by eating undercooked
pork, which can result in intestinal tapeworm if the pork
contains larval cysts. Pigs become infected by eating

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tapeworm eggs in the faeces of a human infected witha tapeworm. Both the tapeworm infection, also known
as taeniasis, and cysticercosis occur globally. The highest
rates of infection are found in areas of Latin America, Asia
and Africa that have poor sanitation and free-ranging pigs
that have access to human feces. US CDC
DNA virus: A virus containing DNA as its genetic material
and using a DNA–dependent DNA polymerase during
replication. Most of these viruses must enter the hostnucleus before they can replicate because they need thehost cell‘s DNA polymerases when replicating their viralgenome. Biology Online
Droplet transmission: Respiratory infections can betransmitted through droplets of different sizes whena person is in in close contact with someone who iscoughing or sneezing and is therefore at risk of having
his/her mouth and nose or eyes exposed to potentially
infective respiratory droplets. According to current
evidence, COVID-19 virus is primarily transmitted between
people through respiratory droplets and contact routes. In
an analysis of 75,465 COVID-19 cases in East Asia, airborne
transmission was not reported. WHO
Early warning systems: Complex tools and processes
aiming to reduce the impact of natural hazards byproviding timely and relevant information in a systematicway. UNDP
Eastern equine encephalitis virus (EEE virus) is spreadby mosquitoes and is a rare cause of brain infections(encephalitis). It can infect horses, causing fever,behavioural changes, and other symptoms of encephalitis,
and infection is often deadly for the horse. Only a few
human cases are reported in the United States each year,
most in eastern or Gulf Coast states. Approximately 30
per cent of people with eastern equine encephalitis die
and many survivors have ongoing neurologic problems.
US CDC
Ebola virus disease (EVD): A rare and deadly disease inpeople and nonhuman primates. The viruses that cause
Ebola are located mainly in sub-Saharan Africa. People can
get Ebola through direct contact with an infected animal(bat or nonhuman primate) or a sick or dead person
infected with Ebolavirus. US CDC
Echinococcosis: A parasitic disease that occurs in two
main forms in humans: cystic echinococcosis (alsoknown as hydatidosis or hydatid disease) and alveolar
echinococcosis, caused by the tapeworms. Dogs, foxes
and other carnivores harbour the adult worms in theirintestine and evacuate the parasite eggs in their faeces.
If the eggs are ingested by humans, they develop into66

larvae in several organs, mainly the liver and lungs. Bothcystic and alveolar echinococcosis are characterized byasymptomatic incubation periods that can last many
years until the parasite larvae evolve and trigger clinicalsigns. Both diseases can cause serious morbidity anddeath. Treatment is often difficult. The disease occurs inmost areas of the world and currently affects about one
million people. Prevention of cystic disease is by treatingdogs that may carry the disease and vaccination of sheep.
WHO
EcoHealth: An emerging field that examines thecomplex relationships among humans, animals and theenvironment, and how these relationships affect thehealth of each of these domains. One Health deals withbiomedical questions, with an emphasis on zoonoses,
and is historically more health science-driven. In contrast,
the EcoHealth concept is defined as an ecosystemapproach to health, tending to focus on environmental
and socio-economic issues and initially designed bydisease ecologists working in the field of biodiversity
conservation. Roger et al. 2016; Lisitza and Wolbring2018
Ecosystem: A dynamic complex of vegetable, animaland microorganism communities and their nonliving
environment that interact as a functional unit. Ecosystems
may be small and simple, like an isolated pond, or large
and complex, like a specific tropical rainforest or a coral
reef in tropical seas. IUCN
Ecosystem degradation: A long-term reduction in an
ecosystem’s structure, functionality, or capacity to provide
benefits to people. IPBESEl Niño: The term refers to the large-scale oceanatmosphere climate interaction linked to a periodic
warming in sea surface temperatures across the central
and east-central Equatorial Pacific. El Niño and La Niña areopposite phases of what is known as the El Niño-Southern
Oscillation (ENSO) cycle. The ENSO cycle is a scientific termthat describes the fluctuations in temperature between
the ocean and atmosphere in the east-central Equatorial
Pacific (approximately between the International DateLine and 120 degrees West). El Niño is sometimes referred
to as the warm phase of ENSO, and La Niña as the cold
phase of ENSO. These deviations from normal surface
temperatures can have large-scale impacts not only on
ocean processes, but also on global weather and climate.
US NOAA
Emerging infectious disease: Infections that haverecently appeared within a population or those whose
incidence or geographic range is rapidly increasing or
threatens to increase in the near future. Baylor Collegeof Medicine

Glossary

Preventing the next pandemic:
Zoonotic diseases and how to break the chain of transmission

Endemic disease: The constant presence and/or usual
prevalence of a disease or infectious agent in a population
within a geographic area. US CDC

responsibilities in combating diseases which have a severe
impact on health and the economy, particularly zoonoses.
FAO; OIE; WHO

Endemic zoonoses are found throughout the developingworld, wherever people live in close proximity to theiranimals, affecting not only the health of poor people
but often also their livelihoods through the health oftheir livestock. Unlike newly emerging zoonoses that
attract the attention of the developed world, theseendemic zoonoses are by comparison neglected. This is,in part, a consequence of under-reporting, resulting inunderestimation of their global burden, which in turnartificially downgrades their importance in the eyes ofadministrators and funding agencies. Maudlin et al. 2009

Fomite transmission refers to the transmission of
infectious diseases by objects. It occurs when an
inanimate object contaminated with or exposed to
infectious agents (such as pathogenic bacteria, viruses
or fungi) serve as a mechanism for transfer to a new host.
Verywell Health[The] environment: The natural world, as a whole or ina particular geographical area, especially as affected byhuman activity. Oxford Dictionary

Great apes: The great apes have traditionally comprised
six species—chimpanzee, bonobo, Sumatran orangutan,
Bornean orangutan, eastern gorilla and western lowland
gorilla. In 2017 scientists identified a third orangutan
species: the Tapanuli orangutan (Pongo tapanuliensis),which is restricted to South Tapanuli, on the island of
Sumatra, in Indonesia, and is on the critically endangered
species list. Great Apes Survival Partnership; Nater et al.
2017

Environment health vs environmental health:‘Environment health’ refers to the health of theenvironment and is used in this report to distinguish itfrom the term ‘environmental health’, which is the branchof public health concerned with all aspects of the naturaland built environment affecting human health. (Authors of
this report)
Epidemic: The occurrence in a community or region ofcases of an illness, specific health-related behaviour, orother health-related events clearly in excess of normal
expectancy. The community or region and the period inwhich the cases occur are specified precisely. WHO
False negative: A test result that wrongly indicates thata particular condition or attribute is absent. Oxford
Dictionary
False positive: A test result which wrongly indicates thata particular condition or attribute is present. Oxford
Dictionary
FAO, OIE, WHO Tripartite Alliance: A collaboration
between the Food and Agriculture Organization (FAO),
the World Organisation for Animal Health (OIE) and theWorld Health Organization (WHO) to address risks fromzoonoses and other public health threats existing andemerging at the human-animal-ecosystems interface andprovide guidance on how to reduce these risks. These
three organisations have worked together for many years
to prevent, detect, control and eliminate health threats
to humans, originating—directly or indirectly—fromanimals. Putting the ‘One Health’ vision into practice has
been facilitated by a formal alliance the three organisations
established in 2010, acknowledging their respective

Glossary

Food value chains comprise all the stakeholders who
participate in the coordinated production and valueadding activities that are needed to make food products.
FAO

Great ape range states: The 21 countries in Equatorial
Africa and in 2 countries in Southeast Asia where the great
apes—chimpanzees, bonobos, gorillas and orangutans—
dwell, forage, reproduce and migrate. WWF
Guano: The excrement of seabirds and bats, used as
fertilizer. Oxford Dictionary
Habitat: The natural home or environment of an animal,
plant or other organism. Oxford Dictionary
Habitat fragmentation: A general term describing the setof processes by which habitat loss results in the divisionof continuous habitats into a greater number of smaller
patches of lesser total and isolated from each other by amatrix of dissimilar habitats. Habitat fragmentation may
occur through natural processes (e.g., forest and grassland
fires, flooding) and through human activities (forestry,
agriculture, urbanization). Habitat loss and fragmentation
have long been considered the primary cause forbiodiversity loss and ecosystem degradation worldwide.
Habitat fragmentation often refers to the reduction ofcontinuous tracts of habitat to smaller, spatially distinct
remnant patches. Although some habitats are naturally
patchy in terms of abiotic and biotic conditions, humanactions have profoundly fragmented landscapes acrossthe word, altering the quality and connectivity of habitats.
IPBES; Wilson et al. 201567

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Highly pathogenic avian influenza (HPAI): A highly
contagious disease caused by viruses that occur mainly
in birds and that can be deadly, especially in domestic
poultry. Since 2003, an Asian HPAI H5N1 virus has resulted
in high mortality in poultry and wild birds in Asia, theMiddle East, Europe and Africa and has become endemic
in some countries. US CDC
Host: An organism infected with or fed upon by a parasitic
or pathogenic organism (for example, a virus, nematode,
fungus). An animal or plant that nourishes and supports aparasite; the host does not benefit and is often harmed by
the association. Biology Online
Host plasticity: The ability of a virus to infect a diverse
range of hosts, such as bats, rodents, and primates.
UC Davis One Health Institute
Human T-cell lymphotropic virus (HTLV): HTLV is a typeof retrovirus that infects a type of white blood cell calleda T-lymphocyte. HTLV can cause cancer. Simian T-cellleukemia viruses (STLVs) that infect Old World monkeys
are the simian counterparts of HTLV, and these viruses arecollectively called primate T-cell leukemia viruses (PTLVs).
The close relationship between HTLV type 1 and STLV
type 1 suggests a simian origin for HTLV type 1 as a resultof multiple interspecies transmissions between primatesand humans and also between different primate species.
Courgnaud et al. 2004
Infectivity: In epidemiology, infectivity is the ability of apathogen to enter, survive and multiply in the host andultimately establish an infection. A pathogen’s infectivity
is subtly but importantly different from its transmissibility,
which refers to a pathogen’s capacity to spread from one
organism to another. UCLA Fielding School of Public
Health; Wikipedia
Inflammatory bowel disease (IBD): An umbrella term
for two disorders that involve chronic inflammation of
the digestive tract—Crohn’s disease and ulcerative colitis,which are characterized by chronic inflammation of thegastrointestinal tract, which is damaged by prolonged
inflammation. US CDC
Japanese encephalitis virus (JEV): A flavivirus related todengue, yellow fever, and West Nile viruses and spread bymosquitoes. It is found principally in Asia and the Western
Pacific and is the main cause of viral encephalitis in many
countries of Asia, with an estimated 68,000 clinical cases
every year. There is no cure for the disease. WHO
La Niña: La Niña episodes represent periods of belowaverage sea surface temperatures across the eastcentral Equatorial Pacific. During a La Niña year, winter68

temperatures are warmer than normal in the Southeast
and cooler than normal in the Northwest Pacific. Global
climate La Niña impacts tend to be opposite those of El
Niño impacts. See also El Niño. US NOAA
Leishmaniasis: A disease caused by the protozoan
Leishmania parasites which are transmitted by thebite of infected sandflies. There are three main formsof leishmaniases—visceral (also known as kala-azar,
which is usually fatal if untreated), cutaneous (the mostcommon) and mucocutaneous. The disease affects someof the poorest people on earth and is associated withmalnutrition, population displacement, poor housing
and a weak immune system. Leishmaniasis is linked toenvironmental changes such as deforestation, building ofdams, irrigation schemes and urbanization. An estimated700,000 to 1 million new cases occur annually. WHO
Leptospirosis: A bacterial disease affecting humans andanimals caused by bacteria of the genus Leptospira. In
humans, it can cause a wide range of symptoms suchas fever, headache, diarrhoea, muscle ache. Without
treatment, Leptospirosis can lead to kidney damage,meningitis (inflammation of the membrane around thebrain and spinal cord), liver failure, respiratory distress,and even death. The bacteria that cause leptospirosis
are spread through the urine of infected animals, which
can get into water or soil and can survive there for weeks
to months. Many different kinds of wild and domestic
animals carry the bacterium. US CDC
Listeriosis: Foodborne listeriosis, caused by the bacteria
Listeria monocytogenes, is one of the most serious
and severe foodborne diseases. It is a relatively raredisease but the high rate of death associated with thisinfection makes it a significant public health concern.
Listeria monocytogenes are widely distributed in nature.
They can be found in soil, water, vegetation and thefaeces of some animals and can contaminate foods.
Vegetables may be contaminated through soil or theuse of manure as fertilizer. Ready-to-eat food can also
become contaminated during processing and the bacteria
can multiply to dangerous levels during distribution
and storage. Unlike many other common foodborne
diseases causing bacteria, L. monocytogenes can survive
and multiply at low temperatures usually found inrefrigerators. WHO
Lockdown: A state of isolation or restricted accessinstituted as a security measure. Oxford Dictionary
Middle East respiratory syndrome (MERS): A viral
respiratory disease caused by a novel coronavirus (Middle
East respiratory syndrome coronavirus, or MERS-CoV) thatwas first identified in Saudi Arabia in 2012. Typical MERS
symptoms include fever, cough and shortness of breath.

Glossary

Preventing the next pandemic:
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Approximately 35 per cent of reported patients withMERS have died. The virus does not seem to pass easily
from person to person and most human cases of MERS
have been attributed to human-to-human infections inhealth care settings. The largest outbreaks have occurredin Saudi Arabia, United Arab Emirates and the Republic ofKorea. Current scientific evidence suggests that dromedarycamels are a major reservoir host for MERS-CoV and an
animal source of MERS infection in humans. WHO
Middle East respiratory syndrome coronavirus (MERSCoV): A coronavirus causing Middle East respiratory
syndrome (MERS). WHO
Molecular epidemiology: A discipline that uses molecularor genetic markers to trace the development of a disease ina population and to understand transmission as well as the
population structure and evolution of bacterial pathogens.
ScienceDirect
Multidisciplinary: Combining or involving several
academic disciplines or professional specializations in an
approach to a topic or problem. Oxford Dictionary
Natural environment: All living and non-living things that
occur naturally on a particular region where human impact
is kept under a certain limited level. Biology Online
Neglected zoonotic diseases include anthrax, brucellosis,
foodborne trematodiases, human African trypanosomosis,
leishmaniasis, leptospirosis, non-malarial febrile illnesses,
schistosomiasis, rabies and taeniasis/cysticercosis.
These neglected zoonoses are found in communities
in low-resource settings across the world, where they
impose a dual burden on people’s health and that of the
livestock they depend upon. Their management requires
collaborative, cross-sectoral efforts of human and animal
health systems and a multidisciplinary approach thatconsiders the complexities of the ecosystems where
humans and animals coexist. Where feasible, preventing
and mitigating their occurrence in humans requires
their elimination in their animal reservoirs. National
governments are increasingly implementing control
programmes to address these burdens. These initiatives
have been strongly endorsed by the Food and Agriculture
Organization of the United Nations, the World Organisation
for Animal Health and World Health Organization Tripartite
and financially supported the international community,
including the Bill & Melinda Gates Foundation, the UK
Department for International Development, the European
Union, the International Development Research Centre and
CGIAR. WHO
Non-random and random sampling: In random datacollection, every individual observation has equal

Glossary

probability to be selected into a sample and there should
be no pattern when drawing a sample. Although random
sampling is generally the preferred survey method,
few people doing surveys use it because of prohibitive
costs. The method requires numbering each member ofthe survey population, whereas nonrandom sampling
involves taking every nth member. Findings indicatethat as long as the attribute being sampled is randomly
distributed among the population, the two methods
give essentially the same results. If the attribute is not
randomly distributed, the two methods give radicallydifferent results. In some instances the nonrandom
methods yield much better inferences about the
population; in other instances, its inferences are muchworse. Rand Corporation; Statistics Solutions
One Health: A collaborative, multisectoral, and transdisciplinary approach—working at local, regional,
national and global levels—to achieve optimal health andwell-being outcomes recognizing the interconnections
between people, animals, plants and their sharedenvironments. One Health Commission
Pandemic: The worldwide spread of a new disease. An
influenza pandemic occurs when a new influenza virus
emerges and spreads around the world and most people
do not have immunity. WHO
Pathogen: Any microorganism able to cause disease in ahost organism. British Society for Immunology
Pathogenicity: The absolute ability of an infectious agent
to cause disease/damage in a host—an infectious agent iseither pathogenic or not. ScienceDirect
Peridomestic: Pertaining to living in and aroundhuman habitations. The rat is a peridomestic animal.
WordSense Dictionary
Permafrost: A thick subsurface layer of soil that remains
frozen throughout the year, occurring chiefly in polar
regions. Oxford Dictionary
Phylogenetic analysis: Phylogeny is the relationshipbetween all the organisms on Earth that have descended
from a common ancestor, whether they are extinct or
extant. Phylogenetics is the science of studying theevolutionary relatedness among biological groups anda phylogenetic tree is used to graphically represent thisevolutionary relation related to the species of interest.
ScienceDirect
Planetary health is defined as “the achievement of thehighest attainable standard of health, wellbeing, andequity worldwide through judicious attention to the69

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human systems—political, economic, and social—that
shape the future of humanity and the Earth’s natural
systems that define the safe environmental limits within
which humanity can flourish. Put simply, planetary
health is the health of human civilization and the stateof the natural systems on which it depends”. In 2014 theRockefeller Foundation and The Lancet jointly formed theCommission on Planetary Health to review the scientificbasis for linking human health to the underlying integrityof Earth’s natural system. The Rockefeller Foundation–
Lancet Commission on Planetary Health
Porcine epidemic diarrhoea (PED): A non-zoonotic viraldisease of pigs caused by a coronavirus and characterized
by watery diarrhoea and weight loss. First identified
and reported in 1971, it affects pigs of all ages, but most
severely neonatal piglets, reaching a morbidity andmortality of up to 100 per cent, with mortality decreasing
as age increases. It is a contagious disease transmissible
mainly by the faecal-oral route. The prevention andmanagement control are focused on strict biosecurity
and early detection. There is no specific treatment for the
disease. WHO
Pristine areas: Pristine means still in its original condition,such as a forest that hasn’t been logged or damaged byhumans. YourDictionary
Q fever: A disease caused by bacteria of the species
Coxiella burnetii. This bacterium naturally infects someanimals, such as goats, sheep and cattle. These bacteria
are found in the birth products (i.e. placenta, amniotic
fluid), urine, faeces and milk of infected animals. People
can get infected by breathing in dust that has been
contaminated by infected animal faeces, urine, milk andbirth products or by eating contaminated unpasteurized
dairy products. Some people never get sick; those who do
usually develop flu-like symptoms. In a small percentageof people, the infection can resurface years later. This more
deadly form of Q fever can damage the heart, liver, brain
and lungs. US CDC
R is the basic reproduction number (also called the ‘basic
0
reproduction ratio’ or ‘rate’ or the ‘basic reproductive
rate’). It refers to the expected number of secondary
infections arising from a single individual during his or
her entire infectious period, in a population of susceptible
individuals. This concept is fundamental to the study of
epidemiology and within-host pathogen dynamics. Most
importantly, R0 often serves as a threshold parameter thatpredicts whether an infection will spread. Heffernan etal. 2005
Rabies: A vaccine-preventable, zoonotic, viral disease.
Once clinical symptoms appear, rabies is virtually 100
per cent fatal. It can spread to people and pets if they70

are bitten or scratched by a rabid animal. In up to 99
per cent of cases, domestic dogs are responsible forrabies virus transmission to humans but it can affectboth domestic and wild animals. The virus can cause
disease in the brain, ultimately resulting in death. Rabies
is present on all continents, except Antarctica, with over
95 per cent of human deaths occurring in the Asia andAfrica regions. Rabies is one of the ‘neglected tropicaldiseases that predominantly affects poor and vulnerable
populations who live in remote rural locations. Although
effective human vaccines and immunoglobulins exist for
rabies, they are not readily available or accessible to thosein need. WHO
Recombinant DNA: The joining together of DNA
molecules from different organisms and inserting it intoa host organism to produce new genetic combinations
that are of value to science, medicine, agriculture andindustry. The DNA sequences used in the constructionof recombinant DNA molecules can originate fromany species. For example, plant DNA may be joined tobacterial DNA, or human DNA may be joined with fungal
DNA. In addition, DNA sequences that do not occur
anywhere in nature may be created by the chemical
synthesis of DNA and incorporated into recombinantmolecules. Using recombinant DNA technology andsynthetic DNA, any DNA sequence may be created
and introduced into any of a very wide range of livingorganisms. Encyclopedia Britannica; Biology Online;
Wikipedia
Reservoir: The habitat in which the agent normally lives,
grows, and multiplies. Reservoirs include humans, animals,
and the environment. The reservoir may or may not be
the source from which an agent is transferred to a host.
US CDC
Reservoir host: A primary host that harbours apathogen but shows no ill effects and serves as a sourceof infection. Once discovered, natural reservoirs elucidate
the complete life cycle of infectious diseases, providing
effective prevention and control. Biology Online
Rift Valley fever (RVF): A mosquito-borne viral zoonotic
disease that affects sheep, goats, cattle and camels,causing devastating losses, especially among pastoral
communities that rely on livestock for their livelihoods.
The disease occurs in explosive outbreaks following
periods of above-normal and persistent rainfall. People
can become infected with Rift Valley fever after being
bitten by an infected mosquito or through close contact
with acutely infected animals or their tissues. In people,
the disease manifests itself as a mild influenza-like
syndrome in over 80 per cent of cases or a severe disease
with haemorrhagic fever, encephalitis or retinitis in a few
cases. Because of its episodic occurrence and predilection

Glossary

Preventing the next pandemic:
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for remote pastoral areas, the impact of the disease
is often exacerbated by delays in the deployment ofprevention and control measures. Livestock vaccination isregarded as the most reliable method for controlling thedisease. ILRI
RNA viruses are those containing RNA as its genetic
material. The RNA may be single stranded or double
stranded. Examples of RNA viruses include Reoviruses,
Picornaviruses, Togaviruses, Orthomyxoviruses,
Rhabdoviruses, etc. A virus containing RNA as its genetic
material. The RNA may be single stranded or double
stranded. Examples of RNA viruses include Reoviruses,
Picornaviruses, Togaviruses, Orthomyxoviruses andRhabdoviruses. Most RNA viruses replicate in thecytoplasm of the host cells. Examples of humandiseases caused by RNA viruses are SARS, influenza andhepatitis C. Biology Online
Salmonella bacteria cause foodborne illness, commonly
called food poisoning, with symptoms of diarrhoea, feverand stomach cramps. It is estimated that Salmonellacauses one million foodborne illnesses every year in
the United States. In the past few years, outbreaks of
Salmonella illness have been linked to contaminatedcucumbers, pre-cut melon, chicken, eggs, pistachios,
raw tuna, sprouts, and many other foods. US CDC
Severe acute respiratory syndrome (SARS): A viral
respiratory illness caused by a coronavirus, SARSassociated coronavirus (SARS-CoV). First reported in
Asia in 2003, the illness spread to more than two dozen
countries in North America, South America, Europe
and Asia before the SARS global outbreak of 2003 wascontained. Since 2004, no known cases of SARS havereported anywhere in the world. US CDC
Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2): A novel coronavirus causing the 2019–2020 coronavirus 2019 (COVID-19) pandemic. On 11
February 2020, WHO named the new virus SARS-CoV-2
because the virus is genetically related to the coronavirus
responsible for the SARS outbreak of 2003. Whilerelated, the two viruses are different. WHO announced‘COVID-19’ as the name of this new disease on the sameday, following guidelines previously developed with theWorld Organisation for Animal Health (OIE) and the Foodand Agriculture Organization of the United Nations (FAO).
WHO
Social distancing, also called ‘physical distancing’, means
keeping six feet (two meters) of space between yourself
and other people outside of your home, not gathering ingroups, staying out of crowded places and avoiding mass
gatherings. US CDC

Glossary

Simian: Relating to, resembling, or affecting apes ormonkeys. Oxford Dictionary
Sooty mangabey: Also known as the white-crowned or
white-collared mangabey (Cercocebus atys), the sootymangabey is a mostly terrestrial Old World monkey. Its
distribution once ranged from the Casamance River in
Senegal to the Sassandra/Nzo River system. Today, thespecies’ conservation status is ‘near-threatened’, with its
range now restricted to the west coast of Africa in Sierra
Leone, Liberia and the western part of Ivory Coast, wherethese foraging monkeys can be found walking along theforest floor gathering fruits and seeds. Sooty mangabeys
are considered to be mostly extinct in their former
habitats in Senegal, Guinea-Bissau and parts of Guinea.
New England Primate Conservancy
Sustainable agricultural intensification: A concept thatchallenges global agriculture (crops, livestock, forests,
fisheries) to achieve a doubling in world food production
while sustaining the environment in which we live.
Food production efficiency needs to double in order tofeed a growing global population using only currently
available land while protecting our living environmentand conserving natural and agricultural biodiversity.
Sustainable agricultural intensification provides the means
to do this with limited available resources. This ambitionis highlighted in the Sustainable Development Goals. The
resources to achieve this increase in food production will
not increase, so the efficiency with which they are usedwill have to be enhanced to ensure ecosystems services
are maintained. Sustainability also requires ensuring social
equity in the productive and environmental benefits
from sustainable agricultural intensification, otherwise
the poorer sections of the farming population andwomen farmers risk being left behind or displaced by thepromotion of intensification. NRI
Vector: An organism or vehicle that transmits thecausative agent or disease-causing organism from thereservoir to the host. Often thought of as a biting insect
or tick but can be an animal or inanimate object. Manyliving vectors are bloodsucking insects and ticks, whichingest disease-producing microorganisms during a
blood meal from an infected host (human or animal)
and later transmit it into a new host, after the pathogen
has replicated. Often, once a vector becomes infectious,
they are capable of transmitting the pathogen for the
rest of their life during each subsequent bite/blood meal.
Biology Online; WHO
Vector-borne diseases: Human illnesses caused byparasites, viruses and bacteria that are transmitted byvectors. Vector-borne diseases account for more than17 per cent of all infectious diseases, causing more than
700,000 deaths annually. WHO

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Vermin: Wild animals that are believed to be harmful tocrops, farm animals, or game, or that carry disease, e.g.,rodents. Oxford Dictionary
Virion: An entire virus particle, consisting of an outer
protein shell, called a capsid, and an inner core of
nucleic acid, either RNA or DNA. The core confers
infectivity and the capsid provides specificity to the virus.
Encyclopaedia Britannica
Virulence: the degree by which a pathogenic organism
can cause disease in a host. Virulence is the measurementof pathogenicity—the ability of a pathogen to cause
disease. Highly virulent pathogens are more likely tocause disease in a host. The virulence of a pathogen isoften correlated with the so-called virulence factors thatenables an organism to invade a host and cause disease.
Biology Online; LibreTexts
Virus: An infectious agent of small size and simple
composition that can multiply only in living cells ofanimals, plants or bacteria. The name is from a Latin word
meaning “slimy liquid” or “poison.”Encyclopaedia
Britannica
West Nile virus (WNV): A member of the Flavivirus genus
that belongs to the Japanese encephalitis antigenic
complex of the family Flaviviridae. Commonly found in
Africa, Europe, the Middle East, North America and West
Asia, the virus is maintained in nature in a cycle involving
transmission between birds and mosquitoes. Horses andother mammals can be infected along with humans, inwhom it causes neurological disease and death. WHO
Wet market, also called public, informal and traditional
market. The term ‘wet market’ is considered a pejorativeby some, so this report uses the term ‘informal market’. All
these terms refer to a marketplace selling fresh meat,
fish, produce and other perishable goods as distinguishedfrom ‘dry markets’ that sell durable goods such as fabricand electronics. Not all wet markets sell live animals, but
the term is sometimes used to signify a live animal market
in which vendors slaughter animals upon customer
purchase. Wet markets are common in many parts of
the world and include a wide variety of markets, suchas farmers’ markets, fish markets and wildlife markets.
They often play critical roles in urban food security due
to factors of pricing, freshness of food, social interaction,and local cultures. Most wet markets do not trade in wildor exotic animals, but have been linked to outbreaksof zoonotic disease. One such market was believed tohave played a role in the COVID-19 pandemic, although
investigations into whether the virus originated from
non-market sources are ongoing as of April 2020.
BBC; Wikipedia

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Wild meat, more commonly called ‘bushmeat’ (in thisreport, we prefer to use the term ‘wild meat’). Wildlife
makes an essential contribution to food security for many
people worldwide. Estimated bushmeat consumption
in the Congo Basin alone is over 4 million tonnes per
year. For many, wild meat may be the main type of meat
available, an important component of food diversity ora food that contributes to cultural identity. Wild meatis a natural healthy food, although (as with domestic
stock) its use may carry health risks related to zoonoses—
diseases transmitted to humans through the handlingor consumption of animals. Declines in wildlife due toover-hunting or other causes, whether direct (e.g. habitat
degradation) or indirect (e.g. weak governance or climatechange) could significantly affect many people´s foodsecurity and nutritional health. Furthermore, an increasing
number of vertebrate species are being hunted todangerously low levels as a result of increased commercial
demand for meat and medicines, with many now indanger of extinction. FAO
Zika virus: A mosquito-borne flavivirus first identified in
Uganda in 1947 in monkeys. Zika virus disease is caused
by a virus transmitted primarily by Aedes mosquitoes,
which bite during the day. Most people infected with
the Zika virus do not develop symptoms, and thosethat do suffer mild symptoms (fever, rash, conjunctivitis,
muscle and joint pain, malaise or headache) for 2–7 days.
Zika virus infection during pregnancy can cause infants
to be born with microcephaly and other congenital
malformations, known as congenital Zika syndrome, andis associated with other complications of pregnancy,
including preterm birth and miscarriage. Outbreaks ofZika virus disease have been reported in Africa, Asia andthe Americas. WHO
Zoonoses: Diseases that can spread between animals
and people, moving from wild and domesticated animals
to humans and from humans to animals. Every year,
nearly 60,000 people die from rabies, and other zoonotic
diseases such as avian influenza, Ebola and Rift Valley
fever constitute additional threats. These diseases affectnot only human health but also animal health and welfare
by causing lowered productivity (e.g. in terms of milk or
egg quality and safety) or death, with significant harm tofarmer livelihoods and national economies. The current
COVID-19 pandemic is a zoonotic disease. FAO; WHOGlossary

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