Animals and Pandemics
Rethinking the Dynamics between Human Beings and Animals to Combat Pandemics
It seems that Covid-19 has shocked humanity in terms of awareness regarding infectious diseases.
Pandemics used to be a rare, but devastating, sighting throughout history but now seems to have
increased in frequency during the recent decades. SARS-CoV, MERS-CoV, Influenza, Asian Flu, Swine
Flu and Ebola just to name a few. Agreed, some of the aforementioned could be categorised as
epidemics but that does not take away the risk they could potentially pose upon humanity. Alongside
the danger, that the majority of the public now is aware of, we should perhaps look into how these
diseases make their way to us. The dynamics between human beings and animals plays a huge role in
the appearances of new diseases. But aside from stressing the importance of the ‘how?’ throughout
this essay, we should also look into ‘why?’. Why is it that in the recent decades alongside the
demographic growth and climate change, infectious diseases are showing up more frequently? And
finally, how can we lower the probability of new emergences in the coming future?
How Infectious Diseases Spread
Pandemics, more specifically infectious diseases, usually spread through cross-species transmission
between human beings and animals. Does that mean you should put a surgical mask on your dog
straight away? No not at all, pathogens that are found in animals are not necessarily compatible with
humans so no need to cover up man’s best friend. However, for a pathogen to be able to infect humans
it has to undergo certain stages.
1. At first a pathogen exists that is not compatible with humans and is only found amongst
animals.
2. In the stage that follows, the pathogen can be transmitted in a natural condition but has not
achieved a way to transmit between humans. These diseases are usually transmitted through
unhygienic circumstances or animal bites.
3. The third stage consists of being transmittable between human beings.
4. During stage four pathogens undergo evolvement during transmission between humans
usually without the participation of animals. The pathogen can now sustain human-to-human
transition.
5. In the fifth and final stage, the pathogen is exclusive to humans and will, in case of viruses,
keep on evolving.
Hygienic conditions have gradually been improved to combat certain types of pathogens that can be
found in cholera, chronic diarrhoea, hepatitis A, polio and so on. The zoonotic transmissions however,
are increasingly becoming more prevalent due to an increase in human beings interacting with animals.
Domestication, worldwide trade, wet markets and animal husbandry are all areas for breeding grounds
where potential pathogens, could find a gateway towards a zoonotic transmission. Allow me to stress
some of the latest and most devastating zoonotic transmissions.1
1
Pike, Brian L et al. “The origin and prevention of pandemics.” Clinical infectious diseases : an official
publication of the Infectious Diseases Society of America vol. 50, 12, 2010, p. 1637-1638.
The Black Death
Responsible for the death of approximately 200 million people, the Black Death, which swept from
Asia into Europe, finds its origin in the Y. pestis bacteria that caused the Justinian Plague back in ancient
Rome. It is well-known that the bacteria mutated and persevered amongst rodents and occasionally
made the jump into the human population, hence the multiple waves throughout Europe and Asia.
During the 1990’s the World Health Organization stated that the plague till this day, is a re-emerging
infectious disease occasionally showing up in Africa and South-America.
Influenza
Often misquoted as the ‘Spanish Flu’, influenza can be categorised into types namely, A, B, C and D.
For the sake of this essay we will be focusing on type A, since it is prevalent among humans, birds and
pigs. Encountering influenza will at first cause a fever, a cough, some headache and muscle pain, very
similar to the conventional flu aches. What usually followed was a lung infection that resulted in being
fatal for the host, often children and the elderly. With approximately 40 million casualties under its
belt, it doesn’t seem irrational that in 1997 when an avian influenza virus was detected in Hong Kong,
the government decided to kill all the chickens in order to stop the epidemic.2
Ebola
From 2013 till 2016, primarily the continent of Africa was plagued by the Ebola virus. It was first
reported in Guinea from where it spread further throughout West-Africa. The virus causes a viral
haemorrhagic fever and had a death rate of almost 50%. Transmission happened through contact with
blood or body fluids and similar to Covid-19, has its origin from contact with bats. As stated it primarily
spread across Africa but was also detected in the US, Spain and the UK. Luckily thanks to strict
containment and community awareness an enormous large scale spread was prevented.3
Zika Virus
First reported in 1947, the Zika virus was found in Uganda where it was transmitted from a mosquito
unto a pregnant female. The virus remained for a long time within a monkey-mosquito circulation but
eventually humans were able to host. Although only rare cases can result in severe brain or nervous
damage, Zika was usually pretty mild, consisting of a regular fever and or a rash. For baby’s during
pregnancy however, Zika caused damage in cognitive functions. It easily spread throughout a total of
87 countries and was suppressed by controlling mosquito populations and case identification.4
2
Laver, Graeme, and Elspeth Garman. “The Origin and Control of Pandemic Influenza.” Science, vol. 293, no.
5536, American Association for the Advancement of Science, 2001, p. 1776.
3
Bhadoria, Pooja et al. “Viral Pandemics in the Past Two Decades: An Overview.” Journal of family medicine
and primary care vol. 10, 8, 2021, p.2746.
4
Bhadoria, Pooja et al. “Viral Pandemics in the Past Two Decades: An Overview.” Journal of family medicine
and primary care vol. 10, 8, 2021, p.2747.
HIV
Since its discovery as the cause of AIDS, the human immunodeficiency virus has, according to UNAIDS,
infected approximately 79.3 million people. 5(UNAIDS) The virus came about via a zoonotic
transmission which supposedly took place in West and Central Africa. The consumption and trade of
bushmeat, which consists of wild animals such as primates, snakes, rats and so on, played a crucial role
in the transmission. Just as the aforementioned diseases, HIV is descendant of the simian
immunodeficiency virus (SIV) found in primates. After being contracted by a human being the virus
found a way to sustain human transmission through breast-feeding, blood, semen and vaginal
secretions.6 An estimate of 36.3 million people have died from an HIV-related illness since the start of
the pandemic.
Supposedly the five viruses stated above are responsible for the death of an estimate of 286 million
human beings, this without adding re-occurring waves of Y. pestis bacteria and Influenza virus. All
found their way from the animal kingdom towards us via a zoonotic transmission and haven’t been
fully eradicated. Agreed, we have found ways to control and live with certain diseases but doesn’t it
seem more logical to prevent instead of combat? Imagine that, for the sake of this essay, the entire
world could change its habits overnight, how can we prevent zoonotic transmissions? In the following
I will try to illustrate certain solutions towards the opposing threat.
Preventing Zoonotic Transmissions
As previously stated, there is an increase in zoonotic transmission, some originating from wildlife whilst
others from animal husbandry. Combined with an intense globalisation, epidemics are increasingly
becoming pandemics due to the fact that countries are less resilient thanks to the speed at which we
transport goods and ourselves. But this growing trend is not only due to the aforementioned, the Great
Acceleration (fig1.) provides an overview of the intensity of human activity. The ever-growing impact
of human beings on the Earth is starting to show. Loss of tropical forests, an increase of land
domestication, increase in measured greenhouse gases seems to go alongside an increase of
pandemics.7
It makes sense that when the literal
distance between human beings and
wild animals is diminishing, we have
an increase in risk of so called
‘spillover events’ where pathogens
come in play. By changing, simplifying
ecosystems and natural habitats, we
tend to disrupt nature’s predatorprey balance causing reservoirs for
disease-carrying species to survive for
a longer period of time.8
5
Figure 1
UNAIDS, Global HIV & AIDS statistics Fact Sheet, geraadpleegd op 13 januari 2022,
https://www.unaids.org/en/resources/fact-sheet.
6
Joris Hemelaar, “The origin and diversity of the HIV-1 pandemic”, Trends in Molecular Medicine,
Vol 18, 3, 2012, p. 182.
7
Serge Morand. New approach to health and the environment to avoid future pandemics. Animal Sentience,
Wellbeing International, 2020, p. 1.
8
Anne Chin, Gregory L. Simon, Peter Anthamatten, Katharine C. Kelsey, Benjamin R. Crawford, Amanda J.
Weaver, Pandemics and the future of human-landscape interactions, Anthropocene, Volume 31, 2020, p. 2-3.
Avoiding Deforestation
At the time of writing, Earth’s surface is made up of 30.6% of forest what translates to roughly 3 999
million hectares. An average of 3.3 million hectares is lost annually due to deforestation to make way
for various types of agricultural productions. As stated above, loss of biodiversity is often a main factor
in the emergence of zoonotic diseases. NGO’s such as EcoHealth Alliance stated that one in three
disease outbreaks took place in correlation to a change in land-use as a result of deforestation, with
the most recent example being Covid-19.9
It might be in our best interest to reduce deforestation since humans and livestock are more likely to
interact with wild animals. Between 2005 and 2012 the country of Brazil, together with an Amazon
fund, were able to reduce deforestation by 70% in the Brazilian Amazon. It took 1 billion dollars to
support a zoning system towards land-use, market restrictions and satellite monitoring to combat
illegal deforestation. This could be a possible solution to reducing the risk of a zoonotic transmission
since it reduces the chances of a virus spillover by 40%. However, without the intense engagement of
governments and strong public will, initiatives to reduce deforestation are often not sustained for a
long period of time.10
Reducing Climate Change
The increase in greenhouse gasses continues to warm our world. Habitats alongside the disease
reservoirs they carry are shifting their living space and disrupting ecosystems. The disruption in our
climate is assuring that hunter-predator dynamics are being turned upside down. A review of 40 000
species across the world concluded that half of them had moved on due to climate change. The
aggregating human populations alongside new animals results in an increase of probability that viruses
could be exchanged up to 13 000 times more likely. Apart from migration, climate change is ensuring
that suitable habitats are being shrunk down which leads to an increase in density. Therefore promotes
possible spillovers between wildlife and humans. Fighting climate change however might be
humanity’s greatest challenge considering the immense structures such as energy and transport that
are part of our everyday lives.
Urbanization
Alongside an ever-growing population, developed and lesser developed countries are increasingly
urbanizing, what seems like, unused land. Urbanization is more often than not very favourable for
disease reservoirs to thrive. Rats, that are known for zoonotic transmissions, are increasingly becoming
overpopulated in cities where they remain and reproduce, thanks to a constant availability of food.
Locations where human beings and animals might interact are usually public parks, restaurants and
gardens.
It's estimated that by 2030, 60% of the human population will live in an urban setting. It’s the
combination of population growth and changing land use to house these people, that increases the
odds of a zoonotic jump. It’s critical for governments to engage in sustainable housing without
disrupting ecosystems in the future.11
9
Poudel, B. S. Ecological solutions to prevent future pandemics like COVID-19. Banko Janakari, vol 30, 1, 2020,
p.1.
10
Dobson, Andrew P., et al. "Ecology and economics for pandemic prevention." Science 369, 6502, 2020, p. 379.
11
Alimi, Yewande, et al. "Report of the scientific task force on preventing pandemics." Cambridge, MA: Harvard
Chan C-CHANGE and Harvard Global Health Institute, 2021, p12.
Combatting Bushmeat
Wild meat that comes from a non-domesticated animal is being served to millions of people daily on a
global scale. It not only poses a threat to the wellbeing of wild animals, it inadvertently poses a threat
to us. To western countries bushmeat may be seen as something from the past but in Africa and Asia,
the amount of bushmeat consumed annually is estimated at 5 million tonnes. The people who choose
to consume are doing it due to different circumstances such as, poverty, limited access to ‘clean’ meat,
occupation or simply because of their preference since, in some cultures it’s considered as a delicacy.
(bushmeat wet markets and the risk of pandemics 2)When it comes to the occasion of transmission, it
is not necessarily consuming the meat that causes a zoonotic jump, it’s rather the process that occurs
before consumption. Butchering the meat in slaughterhouses or wet markets is where the blood, hair,
gut and urine come together. Combined with the, often poor management of waste, wet markets seem
to be breeding grounds for zoonotic pathogens. 12
In the past and present governing powers have tried combatting bushmeat consumption through
repressive laws, unfortunately as with most repressive actions, it led to a black-market network where
the slightest form of regulation is absent. A more proactive regulated way of management could
benefit both consumer and animal. For example, routine check-ups of wildlife that is being traded
could be monitored for diseases. Secondly, governments should look into regulating hunt and trade of
bushmeat to ensure endangered species their safety. Even more importantly, the participation of wet
markets should be a main priority considering its hazard, mutual understanding and trust are here of
essence if we want to regulate storage, packing and sanitization. Although all these measures could
drastically reduce the probability of an outbreak, it does not entirely rule one out, therefore preventive
healthcare infrastructures against pandemics should be installed.13
Animal Husbandry
In a world where meat consumption is part of our daily routine, we can’t ignore the fact that whilst we
slaughter around 80 billion animals each year, those same animals are possible reservoirs for emerging
diseases. A well-recognized transmission between humans and livestock are for example H5N1 and
H1N1 Influenza.14 The livestock that has the highest probability of infecting us are usually those who
have a low-intensity subsistence such as poultry, they require not that much care in comparison to a
cow and are easily packed in a single shed of up to 50 000 birds. In other words, an outbreak can
happen in an instant, spread enormously and devastate not only the poultry sector but pose a threat
to our wellbeing.15 The meat consumption debate is however a troublesome discussion since people
have a protective manner surrounding it and tend to argue that it’s natural, normal and most of all
necessary for our protein intake.16
12
Wolfe, Nathan D et al. “Bushmeat hunting, deforestation, and prediction of zoonoses emergence.” Emerging
infectious diseases vol. 11, 12, 2005, p. 1823.
13
Colin Scott Peros, Rajarshi Dasgupta, Pankaj Kumar, Brian Alan Johnson,
“Bushmeat, wet markets, and the risks of pandemics: Exploring the nexus through systematic review of scientific
disclosures”, Environmental Science & Policy, Volume 124, 2021, p. 8-9.
14
Anne Chin, Gregory L. Simon, Peter Anthamatten, Katharine C. Kelsey, Benjamin R. Crawford, Amanda J.
Weaver, Pandemics and the future of human-landscape interactions, Anthropocene, Volume 31, 2020, p. 381.
15
Tomley, Fiona M., and Martin W. Shirley. "Livestock infectious diseases and zoonoses." Philosophical
Transactions of the Royal Society B: Biological Sciences 364.1530, 2009, p. 2638-2639.
16
Kristof Dhont, Jared Piazza, Gordon Hodson, “The role of meat appetite in willfully disregarding factory farming
as a pandemic catalyst risk”, Appetite, Volume 164, 2021, p. 2.
A solution to changing our behaviour when it comes to meat consumption might be found in plantbased and lab-grown meat. With a market share of 16% for the first and 7% for the latter, traditional
farm raised meat is slowly but surely losing ground with consumers. Whilst for a lot of people these
alternatives are part of a niche category, fast food chains such as McDonald’s, KFC and Burger King are
actively promoting meat alternatives in effort to raise awareness surrounding traditional meats.17
Alternative take
Since Covid-19 there has been a lot of critique coming from, individuals, organizations and researchers
towards the human-planet-animal imbalance. More often than not the initiators of zoonotic
transmissions, that have briefly been summarized above, are being blamed for the pandemic with a
specific grudge towards livestock. However, there are researches who state that the likelihood of a
pandemic coming out of livestock is very unlikely. They do acknowledge that livestock plays a role in
zoonotic interactions, but is not the initiator for developing new pandemics.
The 8 most important zoonoses, according to the CDC, transmit diseases that rarely found in animals
that are being used for food production. Apart from that, the small amount of zoonoses that can be
found in livestock such as, salmonellosis and brucellosis are already being controlled with knowledgebased measures. Human beings have domesticated animals for tens of thousands of years, therefore
zoonotic diseases have already had their pandemic phase. And even if they re-occur, they usually
remain endemic thanks to knowledge that has been built up over the years. That same knowledge has
been put into practice towards monitoring, controlling and vaccinating our domesticated animals.
Agreed, it sometimes occurs that there’s an outbreak but they rarely transform into pandemics.
Then what about the influenza virus that clearly came from domesticated avian animals? Well, the
recent influenza outbreaks such as in 2009 erupted in highly populated regions where interactions with
ducks, chickens and pigs are very close. Asia is a good example when it comes to developing influenza
variants, thanks to small-scale subsistence farmers, a virus can cycle freely between humans and
animals. What I’m trying to clarify is that, if we could properly manage our livestock, we could
drastically decrease a possible zoonotic transmission. Europe has well-known organized measures such
as movement restrictions, preventive medicine and most important of all, hygienic measures.18
Another, perhaps more sophisticated way of stopping pandemics without changing our habits, is by
creating vaccines that spread themselves throughout an animal population. The idea is pretty
straightforward, capture a wild animal and apply a vaccine to its fur and when released back into its
habitat, the vaccine will be ingested by others. These self-disseminating vaccines could drastically
increase immunity among animals and therefore reduce the risk of a zoonotic transmission towards
human beings. Fortunately field trials and lab testing is ongoing for these self-disseminating vaccines
and are hopefully available in the near future.19
17
Ellen J. Van Loo, Vincenzina Caputo, Jayson L. Lusk, Consumer preferences for farm-raised meat, lab-grown
meat, and plant-based meat alternatives: Does information or brand matter?, Food Policy, Volume 95, 2020, p.
11.
18
Alvseike, Ole, Tore Tollersrud, and Bojan Blagojević. "Are pandemics associated with intensive livestock
production?." Veterinarski glasnik, 2021, p. 34-37.
19
Nuismer, S.L., Bull, J.J. Self-disseminating vaccines to suppress zoonoses. Nat Ecol Evol 4, 2020, p. 1168-1169.
Referring back to Europe’s strict handling of livestock, it’s safe to say that the outbreak of a pandemic
is unlikely to happen in western society. We should therefore address the elephant in the room
namely, Asia and Africa. To reduce risk of spillover events, an international incentive should be a
priority into educating and creating awareness around handling domesticated and non-domesticated
animals. It’s not to be underestimated as to how much time, money and patience it will require to
make sure that the people of Africa and Asia put their cultural traditions aside to ensure the safety of
the public health. Researchers at Harvard already stated that the likelihood of the next pandemic will
be East Africa, South Asia and South East Asia.20
Imagine a worst-case scenario where another, perhaps more deadly, virus finds its way to us via a
zoonotic transmission, preparedness might be our best bet. Harry Fineberg, researcher from the
Washington Institute of Medicine, assisted the WHO during the latest influenza outbreak in 2009.
Aside from that, he also advises the Committee on Achieving Sustainable Global Capacity for
Surveillance and Response to Emerging Diseases of Zoonotic Origin. Sure that’s a mouthful but
nevertheless, the committee’s report states that our current level of preparedness regarding the
emergence of new diseases falls short. The way we created a responsive approach instead of a more
mature system, caused failure in averting the current Covid-19 pandemic. Early detection should be a
top priority considering our intense global interactions. The way we are able to cross continents in a
single day poses difficulties as to how we can control the spread of new diseases.21Furthermore, BMJ
Global Health created an Epidemic Preparedness Index which states that the most prepared countries,
are located in Europe and North America. On the other hand, the least prepared where found to be
located in West Africa and Southeast Asia. Referring to the statement made above, it’s clear that the
latter countries have a higher risk of, not only producing a new pathogen but will likely also fail in
combatting spread. This due to a shortage in economic resources, institutional capacities , public
health communication and infrastructure.22
20
Alimi, Yewande, et al. "Report of the scientific task force on preventing pandemics." Cambridge, MA: Harvard
Chan C-CHANGE and Harvard Global Health Institute, 2021, p6.
21
ike, Brian L et al. “The origin and prevention of pandemics.” Clinical infectious diseases : an official
publication of the Infectious Diseases Society of America vol. 50, 12, 2010, p. 1639.
22
Oppenheim, Ben & Gallivan, Mark & Madhav, Nita & Brown, Naor & Serhiyenko, Volodymyr & Wolfe, Nathan
& Ayscue, Patrick, “Assessing global preparedness for the next pandemic: Development and application of an
Epidemic Preparedness Index”, BMJ Global Health, 2019, p1-2.
Moving Forward
Ever since human beings were able to record their steps by writing down their history, diseases,
endemics, pandemics have been a part of it. Whether is was the wrath of God, or multiple gods, it
seems as if we’ve been trying to figure out where these things came from. Thanks to science, we are
made aware of the opportunities and dangers that lay beyond the naked eye with zoonotic pathogens
being one of the latter. Since we now understand how our interactions with animals have their
consequences, in the aftermath of the height of the Covid pandemic, our priority should be in avoiding
another new, possibly more deadlier virus.
It’s been made clear that the origin of a zoonotic transmission consists of a complex interaction
between human beings, wild animals, domesticated animals and cultural differences. On top of that
we clearly lack a preventive pandemic infrastructure. Aside from that, it’s also been made clear that a
worldwide population growth, that doesn’t seem to be stopping, is increasing our demands from our
Earth in terms of land and energy. The combination of shrinking the buffer between wild animals from,
humans as well as our domesticated animals, is increasing the probability of zoonotic transmission.
Alongside poor hygiene and lack of surveillance in specifically Africa and Southeast Asia, it seems that
the probability of a new virus isn’t that low.
I believe that throughout this essay I’ve highlighted some possible, I wouldn’t call it solutions, but
preventive measures that could lower the odds of a new pandemic drastically. A good start would be
a behavioural change amongst wild animal consumers and producers. Informative incentives, controlintervention and most importantly economic aid for wild meat producers could decrease trade and
consumption. On the other hand, it might not be necessary to try and decrease wild meat exchanges
since people tend to have strong feelings towards their meat consumption. Therefore a more
sustainable method of approach might be setting up infrastructures to ensure hygienic processes.
Following newly set-up infrastructures, a global network could encourage surveillance of humans,
livestock and more importantly wildlife. This would improve detection of disease emergence and in
case of a zoonotic jump, early warning systems could alert and avoid further spreading.
A promising method of protecting human beings from pathogens, that stem from wild animals, could
be vaccinating wildlife. In a way it’s comparable to the way we’ve managed to control rabies amongst
dogs, however it seems that preventing pathogens by interrupting transmission amongst wild species,
is difficult to implement as it is not entirely ready yet.
Nevertheless whether it’s regulating bushmeat, investing in a preventive pandemic infrastructure,
encouraging vaccination amongst wild animals, it seems that we can’t pinpoint the exact cause of
zoonotic transmitted pandemics. A simple question as “should we stop consuming meat to prevent
pandemics?” will result in a complex answer where both “yes” and “no” will be present. Let me be
clear as to whether we can avoid a next pandemic, we cannot. We can only improve our chances in
avoiding, and combatting one. Therefore we should globally, and global cooperation is highly essential,
invest in defending ourselves from all possible breeding grounds of pathogens.
Bibliography
Literature
Alimi, Yewande, et al. Report of the scientific task force on preventing pandemics, Cambridge, MA:
Harvard Chan C-CHANGE and Harvard Global Health Institute, 2021.
Alvseike, Ole, Tore Tollersrud, and Bojan Blagojević, Are pandemics associated with intensive livestock
production?, Veterinarski glasnik, 2021.
Anne Chin, Gregory L. Simon, Peter Anthamatten, Katharine C. Kelsey, Benjamin R. Crawford, Amanda
J. Weaver, Pandemics and the future of human-landscape interactions, Anthropocene, Volume 31,
2020.
Bhadoria, Pooja et al. Viral Pandemics in the Past Two Decades: An Overview, Journal of family
medicine and primary care vol. 10, 8, 2021.
Colin Scott Peros, Rajarshi Dasgupta, Pankaj Kumar, Brian Alan Johnson, Bushmeat, wet markets, and
the risks of pandemics: Exploring the nexus through systematic review of scientific disclosures,
Environmental Science & Policy, Volume 124, 2021.
Dhont, Kristof, Jared Piazza, Gordon Hodson, The role of meat appetite in wilfully disregarding factory
farming as a pandemic catalyst risk, Appetite, Volume 164, 2021,
Dobson, Andrew P., et al. Ecology and economics for pandemic prevention, Science vol 369, 2020.
Laver, Graeme, and Elspeth Garman. The Origin and Control of Pandemic Influenza, Science, vol. 293,
American Association for the Advancement of Science, 2001.
Nuismer, S.L., Bull, J.J. Self-disseminating vaccines to suppress zoonoses. Nat Ecol Evol 4, 2020.
Oppenheim, Ben & Gallivan, Mark & Madhav, Nita & Brown, Naor & Serhiyenko, Volodymyr & Wolfe,
Nathan & Ayscue, Patrick, Assessing global preparedness for the next pandemic: Development and
application of an Epidemic Preparedness Index. BMJ Global Health, 4, 2019.
Pike, Brian L et al. The origin and prevention of pandemics, Clinical infectious diseases : an official
publication of the Infectious Diseases Society of America vol. 50, 2010.
Poudel, Buddi, Ecological solutions to prevent future pandemics like COVID-19, Banko Janakari, 2020.
Serge Morand. New approach to health and the environment to avoid future pandemics, Animal
Sentience, Wellbeing International, 2020.
Tomley, Fiona M., and Martin W. Shirley. Livestock infectious diseases and zoonoses, Philosophical
Transactions of the Royal Society B: Biological Sciences 364, 2019.
UNAIDS
Wolfe, Nathan D et al. Bushmeat hunting, deforestation, and prediction of zoonoses
emergence, Emerging infectious diseases vol. 11, 2005.