By Patricia Lee
“It is that range of biodiversity that we must care for – the whole thing – rather than just one or two stars,” David Attenborough.
The development of modern societies in the last 50 years has penetrated previously untouched natural systems. Unsustainable practices jeopardize the future of the planet and lead to ever-increasing biodiversity and ecosystem loss. Land degradation, water scarcity, increased pollution, climate fluctuations and biodiversity loss at unprecedented rates have an impact on human health, increasing the outbreaks of infectious diseases. If not addressed, the overexploitation of natural resources threatens the future of both human and planetary health.
On the 31st of December of 2019, the World Health Organisation (WHO) was alerted about the detection of a novel virus found in China. Belonging to the coronavirus family, Covid-19 is a new disease caused by the SARS-CoV-2 virus. Almost a month after the virus was first identified, the WHO declared a global health emergency. By March 11th there were cases in over 110 countries; within days, Covid-19 was declared a pandemic. Clinical trials began soon after, generating data from around the world to find and develop an effective treatment. The world has not been the same since.
For the international scientific community, pandemics like the Coronavirus Covid-19 are the continuation of a pattern of increasingly frequent infectious disease outbreaks. The incidence of influenza, malaria, and ebola are proving that the spread of serious diseases remains a leading source of human mortality. However, the detection of new, potentially devastating pathogens is nothing new for science. Scientists, journalists and researchers first saw the impending threat of a global pandemic a few decades ago – some studies and articles being published in the mid-nineties – while studying the influenza virus.
With a world experiencing substantial and more frequent pandemic outbreaks, research began to show a strong correlation between the rate of biodiversity loss and the human ability to combat pandemics. The frequency of disease outbreaks in the last 50 years is being linked to the effects of climate change and human intervention. Moreover, the fluctuation of climatic conditions – drastic temperature variations, the improper disposal of waste, forest clearance, extreme weather events and demographic changes, have shown to have a direct influence on health when the balance of the world’s ecological processes is disturbed.
This article aims to explore and discuss the relation between biodiversity loss (genetic diversity loss) and the emergence/re-emergence of multiple infectious diseases. First, a brief look at some of the most relevant pandemics in history will be provided. Thenceforth, the definition of biodiversity and the concerns regarding ecosystem and biodiversity loss will be discussed. Finally, conclusions will be drawn from a fair examination of the significance that biodiversity has in preserving human health.
Global Pandemics and Human Health
Pandemics have been around since the very formation of the first prehistoric human nomadic groups, and humans have been interacting with their environment since the Palaeolithic era, over 12,000 years ago. The increase of human settlements boosted the development of more trade routes, which in turn, perpetuated the contact between different populations, animals and ecosystems; facilitating the spread of epidemics and pandemics such as tuberculosis, smallpox, cholera and leprosy, to name a few (Daszak, P. et al. 2001).
The European continent, for example, suffered one of the most terrible infectious disease outbreaks back in the 14th Century. Introduced by plague-infected rodents, the ‘Black Death’ claimed the life of 20 million people throughout the years during the many recurrences of the disease (EB, 2020). Eventually, infection-control measures became prevalent, such as the separation of sick and healthy populations. In 1377, the port of Ragusa -modern Croatia- established a place outside the city to treat the sick; this tradition named ‘trentino’ and ‘quarentino’ was a mandatory thirty to forty-day isolation period put in place to avoid the ships arriving from plague-affected areas (Sehdev, 2002; Mayer, 2018) – a practice that later came to be known as ‘quarantine’.
The devastating 1918 influenza pandemic – considered one of the deadliest influenza pandemics recorded in recent history – had an estimated loss of about one-third of the world’s population (CDC, 2005). The virus had high mortality in healthy, young and elderly people, and at the time, the properties which made it so devastating were not understood. Thus, control efforts were insufficient, inconsistent and limited. Influenza-like viruses, such as the H1N1virus, have been identified as a direct descendent of the 1918 virus (Taubenberger, J. et al. 2006)
The last time the world had a close view of what a pandemic could look like was a little over a decade ago when, in 2009, the H1N1 swine flu infected as many as 1.4 billion people globally (Ross, 2012; CDC, 2020). The virus was first detected in the United States and found in more than 214 countries, territories and communities within months (WHO, 2009). Comparatively, pandemics such as the 1981 HIV/AIDS global pandemic, resulted in more than 36 million lives lost; before that, the 1968 influenza pandemic - A (H3N2) had taken the lives of more than 1 million people (WHO, 2017).
Smith, K.F. et al., (2014) stated that for the past 30 years disease outbreaks have grown steadily, becoming recurrent and more diverse; their research draws attention to the fact that during the period between 1980 and 2013 more than 12,000 outbreaks were found around the world. However, significant progress has been made in the response to other infectious diseases. In the case of Ebola in West Africa, an outbreak of unprecedented scale between 2014 and 2016 was successfully contained, although some areas remained on high alert (Coltart, C.E., et al. 2017). Undoubtedly, the unprecedented crisis resulting from the social and economic consequences of Covid-19, will require a more efficient, integrated planning and preparation for pandemics in the future.
Global preparedness means that every country has the capacity to prevent, detect, assess, report and rapidly respond to health threats. Forthwith, there is still much more to do in order to effectively address the root causes behind the increasing incidence of outbreaks.
Biodiversity and Ecosystem Health
Biodiversity can be a complex term. It encompasses the variety of life on Earth and how every living thing from microorganisms to entire ecosystems interact and make the planet habitable. Biological diversity (biodiversity) is defined by the Convention on Biological Diversity as:
"The variability among living organisms from all sources including [among other things], terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems."
Similarly, Maillard & Gonzalez (2006) refer to biodiversity as:
"[…] a reflection of the manifestation of the differences between living entities (species, populations, individuals…) and of the ecological interactions within which species evolve."
The extensive biological diversity of the planet includes millions of known and unknown species that, together, form complex systems and diverse populations (Mergeay and Santamaria, 2012). The diversity of species is the work of 4 billion years of continued evolution. To put it in perspective, humans and their ancestors have been inhabiting the planet for about 6 million years, evolving into the modern form of humans only 200,000 years ago (EB, 2020) representing a mere 0.0005% of Earth’s history.
Presently, there is too much pressure on the natural world. Modern civilization and industrialization have impacted the normal distribution and number of living species, directly affecting ecosystems and the genetic drift and natural evolution of organisms (Maillard J.C. & J.P. Gonzalez, 2006; Hugot & Gonzalez, 2005). For instance, the extinction rate of species is now thought to be in the tens to hundreds of times compared to average over the last 10 million years (UN, 2019). Processes such as deforestation, reforestation, desertification, and urbanization also contribute to changes in climate. Natural changes in the environment, for example, seasonal climate trends like the El Niño and La Niña events, are also associated with a warmer weather (Canberra: Commonwealth of Australia, 2012).
The Joint Statement on Post-2020 Global Biodiversity Framework (WEF, 2020; ICU, 2020; UNEP, 2020) states that:
“Biodiversity conservation is linked to climate change and critical for realising the Sustainable Development Goals, as a diverse and healthy planet and is the foundation of human health, security, well-being and development.”
In this sense, Woodley (2020) argues that currently there are two leading causes of biodiversity loss: 1) habitat loss, mainly on land and 2) overexploitation, primarily in the ocean. Conversely, the 2020 World Economic Forum lists five ways human activity endangers biodiversity: 1) the loss of wetlands, land surface and ocean areas resulting from agricultural and industrial expansion, 2) the exploitation of plants and animals through harvesting, logging, hunting and fishing, 3) the damage of habitats by waste and pollutants derived from industrial, mining and agricultural activities, 4) the introduction of non-indigenous species and 5) climate change. Moreover, many components of biodiversity are used as indicators of human health stressors and tools for mapping and monitoring air and water quality as well as ecosystem health.
The world population of 7.7 billion people (USCB, 2020) represents just 0.01% of all living creatures, however, according to data from the World Economic Forum Global Risk Report 2020, humanity has caused the loss of 83% of wild mammals and half of the plant species. If the services and resources provided by the planet’s rich ecosystems are affected, the stability of the planet could face serious risks. Thus, ensuring the conservation and sustainable use of biological diversity is essential not only for human health but in averting the devastating effects of climate change and ecosystem collapse.
Biodiversity and the Emergence/Re-emergence of Infectious Diseases
According to multiple studies (Daszak, P. et al. 2001; Ezenwa, V. et al. 2006; Mills, J.N. 2006; Woolhouse, M. et al. 2008; Pongsiri, M. J. et al. 2009; Woolhouse, M. et al. 2012; Lacroix, C. et al. 2014; Morand, et al. 2014; Rulli, M.C. et al. 2017) there is a strong link between biodiversity loss and the emergence of infectious diseases. At the same time, the damaging effect of human activities from land use to changing climate seem to provide the perfect opportunity for viruses to spread.
When the natural disease resistance provided from a rich biological diversity is lost, the continuous pressure on ecosystems and biodiversity facilitates the cross of pathogens –the regulators of the ecological balance established over time– from animals to humans (Quammen, 2012). For this reason, maintaining ecosystem integrity by supporting a diversity of species that control the spread of pathogens (Maillard & Gonzalez, 2006) is considered a key factor for the successful management of endemic zoonotic disease. 
The United Nations Environment Program (UNEP) in their 2016 Frontiers Report states that three types of changes are allowing pathogens to make the jump from animal to human hosts: 1) Changes in the environment, 2) behavioural changes in the hosts and 3) changes in the pathogen itself as it evolves. They argue that:
"[…] environmental conditions [...] can enable or disable the survival, reproduction, abundance, and distribution of pathogens, vectors and hosts, as well as the means of disease transmission and the outbreak frequency. "
In addition, scientific findings seem to indicate that presently, pathogens have more opportunities to pass from wild and domestic animals to people, with more than 75% of the emerging zoonoses originating from wildlife in recent times (Canberra: Commonwealth of Australia, 2010; CDC, 2020). Zoonotic diseases affect not only human health but have a considerable impact on the agriculture, economy and environment.
Other environmental disasters and ecological disturbances associated with the emergence of zoonotic diseases are, animal plagues and broken heat records, which are too directly disrupting the balance of natural systems. In the case of the 1990s Nipah virus outbreak in Malaysia, it is believed that the virus was spread from fruit bats moving into peat farms infecting humans as a result of forest fires, deforestation and drought (Mrema M., 2020).
Likewise, wildlife trade exposes the animals to ‘new’ environments altering their physiological responses, affecting their immune function and making them more susceptible to disease (Dohms & Metz, 1991). Moreover, when the body fluids of numerous sick animals in crowded wildlife markets come into contact with humans, the chance of transmission is significantly heightened. As an illustration, infectious diseases like malaria, dengue, yellow fever and sleeping sickness outbreaks are occasional in Northern Gabon, Africa, where people come into direct contact with wild animals while hunting chimpanzees from the forest (Vidal, 2020). Similarly, the Ebola virus, found in fruit bats, is transmitted through contact with an infected animal and spreads from person to person (WHO, 2020).
The rapid and uncontrolled development which the world has seen in the last five decades has not come without a price. Understanding the significance of ecosystems and biodiversity beyond their intrinsic value is fundamentally the first critical step in developing the necessary health initiatives and disease control mechanisms that preserve ecosystem integrity and efficiently regulate the over-exploitation of resources to control the surge in emerging diseases.
Fighting future epidemics will depend not only on the advances in science and improvements in healthcare; it will heavily depend on the human race’s ability to address the consequences of its lifestyle choices by recognising the true value of nature, shifting economic and social systems and acknowledging its capacity to change and push for better laws, encouraging the adoption of effective ecosystem-valuation measures to ensure biodiversity remains protected.
Every loss in nature has an impact on the planet’s delicate balance. When biodiversity is declining, so is the planet’s capacity to support life.
Numerous global environmental changes are simultaneously affecting human health and human activities are undermining the potential productivity of forest, farmland and other ecosystems. More needs to be done collectively to understand the root of these changes and the significant interactions between ecological processes, human health and climate change.
Research clearly shows that biodiversity is a critical environmental determinant of human health. The role it plays in the ability of species to rapidly adapt and survive in modified ecosystems needs to be seen as what it truly is, a barrier or ‘buffer’ against the disease-causing organisms that disrupt immune defence systems.
Today, only 15 per cent of land and 7 per cent of the ocean is protected. The IUCN and UNEP point to the urgent need to protect 30 per cent of the Earth by 2030 and half of the planet by 2050. Halting and reversing degradation is possible through reforestation. The sustainable management of resources is attainable if more policies are developed and enforced to incentivise sustainability. Habitat and species protection are achievable through effective legislation and the adoption of sustainable and productive farming methods, environmental social awareness is possible through education for sustainability. The challenges ahead demand immediate collective action.
The sustainable management of production and consumption is crucial. Safeguarding the future of ecosystems and biodiversity by protecting species, making sustainable choices to maintain a steady climate, increasing the number of conservation areas and developing effective policies to protect them, will make this attainable in the future, however the course must be changed now.
 An event [serious, sudden, unusual or unexpected] that constitutes a public health risk to other States [and carries implications for public health beyond the affected state’s national border] through the international spread of disease and to potentially require a coordinated [and immediate] international response.
 The WHO defines a pandemic as the global spread of a new disease, when most people do not have immunity.
 In 1995, S.S. Morse published an article titled “Factors in the emergence of infectious diseases” where he argued that “Factors precipitating disease emergence […] can include ecological, environmental, or demographic factors that place people that increased contact with a previously unfamiliar microbe or its natural host or promote dissemination. These factors are increasing in prevalence [this] suggests that infections will continue to emerge and probably increase […].” See reference list below.
 Quarentine, comes from the Latin ‘quadraginta’ and the Italian ‘quaranta’, both meaning forty.
 According to the World Health Organization, zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans. [..] zoonoses may be bacterial, viral or parasitic, or may involve unconventional agents. As well as being a public health problem, many of the manor zoonotic diseases prevent the efficient production of food of animal origin and create obstacles to international trade in animal products.
IPBES 2019 Global Assessment Report on Biodiversity and Ecosystem Services. Available: https://ipbes.net/global-assessment
Global Partnership on Forest and Landscape Restoration (2018) Restoring Forests and Landscapes: The Key to a Sustainable Future. Available: http://www.fao.org/in-action/forest-landscape-restoration-mechanism/news-and-events/news-detail/en/c/1150767/
Global Environment Outlook 2019. Available: https://www.unenvironment.org/resources/global-environment-outlook-6
UNEP (2016). UNEP Frontiers 2016 Report: Emerging Issues of Environmental Concern. United Nations Environment Programme, Nairobi. Retrieved from: https://environmentlive.unep.org/media/docs/assessments/UNEP_Frontiers_2016_report_emerging_issues_of_environmental_concern.pdf
Australian Government, Department of Health. (2010). Australia’s notifiable diseases status, 2010: Annual report of the National Notifiable Diseases Surveillance System – Results: Zoonoses. Communicable Diseases Intelligence, Vol 36 No 1 March 2012 (Canberra: Commonwealth of Australia, 2010).
Australian Government, Bureau of Meteorology. (2012). What are El Niño and La Niña events? Accessed the 19th of April 2020. Retrieved from: http://www.bom.gov.au/climate/enso/history/ln-2010-12/ENSO-what.shtml
Daszak, P., Cunningham, A. A., & Hyatt, A. D. (2001). Anthropogenic environmental change and the emergence of infectious diseases in wildlife. Acta tropica, 78(2), 103-116.
Dohms, J.E. & Metz, A. (1991). Stress-mechanisms of immunosuppression. Vet. Immunol. Immunopathol., Nov;30 (1): 89-109.
Centres for Disease Control and Prevention (2020). 1968 Pandemic (H3N2 virus). Retrieved from: https://www.cdc.gov/flu/pandemic-resources/1968-pandemic.html
Centers for Disease Control and Prevention (CDC) 2020. 2009 H1N1 Pandemic (H1N1pdm09 virus). Retreived from: https://www.cdc.gov/flu/pandemic-resources/2009-h1n1-pandemic.html
Coltart, C. E., Lindsey, B., Ghinai, I., Johnson, A. M., & Heymann, D. L. (2017). The Ebola outbreak, 2013-2016: old lessons for new epidemics. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 372(1721), 20160297. https://doi.org/10.1098/rstb.2016.0297
Encyclopedia Britanica, (2020). Influenza pandemic of 1918-19. Accessed April 20th 2020. Retrieved from: https://www.britannica.com/event/influenza-pandemic-of-1918-1919
Ezenwa, V. O., Godsey, M. S., King, R. J., & Guptill, S. C. (2006). Avian diversity and West Nile virus: testing associations between biodiversity and infectious disease risk. Proceedings. Biological sciences, 273(1582), 109–117. https://doi.org/10.1098/rspb.2005.3284
Howard, R. (2020). Human evolution. Britannica. Retrieved from: https://www.britannica.com/science/human-evolution
Hugot, J.P. & J.P. Gonzalez. (2005). Maladies émergentes: un problème sociétal d’avenir. 121-125, In Biodiversité et changements globaux. ADPF/MAE. Paris.
International Union for Conservation of Nature. (2020). Post-2020 Global Biodiversity Framework. Accessed the 20th of April 2020. Retrieved from: https://www.iucn.org/theme/global-policy/our-work/convention-biological-diversity-cbd/post-2020-global-biodiversity-framework
Keusch GT, Pappaioanou M, Gonzalez MC, et al., editors. Sustaining Global Surveillance and Response to Emerging Zoonotic Diseases. National Research Council (US) Committee on Achieving Sustainable Global Capacity for Surveillance and Response to Emerging Diseases of Zoonotic Origin.
King, A. (2020). The hunt for the next potential coronavirus animal host. Accessed the 3rd of April 2020. Retrieved from: https://www.nationalgeographic.com/animals/2020/03/coronavirus-animal-reservoir-research/
Kiprop, V. (2018). How Long Have Humans Been On Earth? World Atlas. Retrieved from https://www.worldatlas.com/articles/how-long-have-humans-been-on-earth.html
Lacroix, C., Jolles, A., Seabloom, E. W., Power, A. G., Mitchell, C. E., & Borer, E. T. (2014). Non-random biodiversity loss underlies predictable increases in viral disease prevalence. Journal of the Royal Society Interface, 11(92), 20130947.
Mayer, J. (2018). The Origin of the Word Quarantine. Science Friday. Retrieved from: https://www.sciencefriday.com/articles/the-origin-of-the-word-quarantine/
Mergeay, J., & Santamaria, L. (2012). Evolution and Biodiversity: the evolutionary basis of biodiversity and its potential for adaptation to global change. Evolutionary applications, 5(2), 103–106. https://doi.org/10.1111/j.1752-4571.2011.00232.x
Mills, J. N. (2006). Biodiversity loss and emerging infectious disease: an example from the rodent-borne hemorrhagic fevers. Biodiversity, 7(1), 9-17.
Morand, S., Jittapalapong, S., Suputtamongkol, Y., Abdullah, M. T., & Huan, T. B. (2014). Infectious diseases and their outbreaks in Asia-Pacific: biodiversity and its regulation loss matter. PLoS One, 9(2).
Morse S. S. (1995). Factors in the emergence of infectious diseases. Emerging infectious diseases, 1(1), 7–15. https://doi.org/10.3201/eid0101.950102
McMichael, T., & McMichael, A. J. (2001). Human frontiers, environments and disease: past patterns, uncertain futures. Cambridge University Press.
Mrema M. (2020). Ban wildlife markets to avert pandemics, says UN biodiversity chief. The guardian. Accessed mon 6 Apr 2020. Retrieved from: https://www.theguardian.com/world/2020/apr/06/ban-live-animal-markets-pandemics-un-biodiversity-chief-age-of-extinction
Ostfeld, R.S. & F. Keesing. (2000). The function of biodiversity in the ecology of vector-borne zoonotic diseases. Canadian Journal of Zoology 1, no. 78, Ottawa, p. 2061-2078.
Rulli, M. C., Santini, M., Hayman, D. T., & D’Odorico, P. (2017). The nexus between forest fragmentation in Africa and Ebola virus disease outbreaks. Scientific reports, 7, 41613.
Ross. (2012). CDC estimate of global H1N1 pandemic deaths: 284,000. Center for Infectious Disease Research Policy. Retrieved from: http://www.cidrap.umn.edu/news-perspective/2012/06/cdc-estimate-global-h1n1-pandemic-deaths-284000
Rosegrant, M.W., Fernandez, M., Sinha, A., Alder, J., Ahammad, H., de Fraiture, C., Eickhour, B., Fonseca, J., Huang, J., Koyama, O., Omezzine, A.M., Pingali, P., Ramirez, R., Ringler, C., Robinson, S., Thornton, P., van Vuuren, D. and Yana-Shapiro, H. (2009). Looking into the future for agriculture and AKST. In McIntyre, B.D., Herren, H.R., Wakhungu, J. and Watson, R.T. (Eds.). International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD): Agriculture at a Crossroads, global report. Washington, DC, USA: Island Press. pp.307- 376. Retrieved from: http://www.unep.org/dewa/agassessment/reports/IAASTD/EN/Agriculture%20at%20a%20Crossroads_Global%20Report%20 %28English%29.pdf
Smith, K.F. et al., (2014). Global rise in human infectious disease outbreaks. Journal of the Royal Society Interface, Vol. 11(101). Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4223919/
Taubenberger, J. K., & Morens, D. M. (2006). 1918 Influenza: the mother of all pandemics. Emerging infectious diseases, 12(1), 15–22. https://doi.org/10.3201/eid1201.050979
Thomas, S., Izard, J., Walsh, E., Batich, K., Chongsathidkiet, P., Clarke, G., ... & Gilligan, J. P. (2017). The host microbiome regulates and maintains human health: a primer and perspective for non-microbiologists. Cancer research, 77(8), 1783-1812.
Treadwell, T. (2008). Convergence of forces behind emerging and reemerging zoonoses, and future trends in zoonoses . Presentation, Institute of Medicine/National Research Council Workshop on Sustainable Global Capacity for Surveillance and Response to Emerging Zoonoses, Washington, DC, June 25–26.
United Nations. (2019). Nature’s Dangerous Decline ‘Unprescedented’; Species Extinction Rates ‘Accelerating.’ Accessed the 19th April 2020. Retrieved from: https://www.un.org/sustainabledevelopment/blog/2019/05/nature-decline-unprecedented-report/
United Nations Environmental Programme. (2020). Coronavirus outbreak highlights need to address threats to ecosystems and wildlife. United Nations. Retrieved from: https://www.unenvironment.org/news-and-stories/story/coronavirus-outbreak-highlights-need-address-threats-ecosystems-and-wildlife
United Nations Environmental Programme. (2016). UNEP Frontiers 2016 Report: Emerging Issues of Environmental Concern. United Nations Environment Programme, Nairobi. Retrieved from: https://environmentlive.unep.org/media/docs/assessments/UNEP_Frontiers_2016_report_emerging_issues_of_environmental_concern.pdf
United States of America, Census Bureau. (2020). 2020 World Population by Country. Accessed the 20 of April 2020. Retrieved from: https://www.census.gov/
Vidal, J. (2020). ‘Tip of the iceberg’: is our destruction of nature responsible for Covid-19? The Guardian, Accessed the 18 March 2020. Retrieved from: https://www.theguardian.com/environment/2020/mar/18/tip-of-the-iceberg-is-our-destruction-of-nature-responsible-for-covid-19-aoe
World Economic Forum. (2019). Outbreak readiness and business impact: protecting lives and livelihoods across the global economy. World Economic Forum, Geneva 2019. Accessed the 21st of April 2020. Retrieved from: https://www.weforum.org/whitepapers/outbreak-readiness-and-business-impact-protecting-lives-and-livelihoods-across-the-global-economy
World Health Organization. (2015). Connecting Global Priorities: Biodiversity and Human Health: A State of Knowledge Review. Accessed the 15th of April 2020. Retrieved from: https://www.who.int/publications-detail/connecting-global-priorities-biodiversity-and-human-health
World Health Organization. (2009). 2009 H1N1: Overview of a Pandemic. Impact of 2009 H1N1. Accessed the 20th of April 2020. Retrieved from: https://www.cdc.gov/h1n1flu/yearinreview/yir5.htm
World Health Organization. (2020). How the World Health Organization works with all people, everywhere. Accessed the 20 of April 2020. Retrieved from: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/events-as-they-happen
Woolhouse, M. E., Howey, R., Gaunt, E., Reilly, L., Chase-Topping, M., & Savill, N. (2008). Temporal trends in the discovery of human viruses. Proceedings of the Royal Society B: Biological Sciences, 275(1647), 2111-2115.
Woolhouse, M., Scott, F., Hudson, Z., Howey, R., & Chase-Topping, M. (2012). Human viruses: discovery and emergence. Philosophical Transactions of the Royal Society B: Biological Sciences, 367(1604), 2864-2871.