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Zoonotic pandemics – viruses, animals, and humans in a globalised world

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In today’s globalised world, the risk of future zoonotic outbreaks and the severity of their impacts increase with a surge in demand for animal-based products. The Food & Pandemics Report directs attention towards risk mitigation and prevention of future outbreaks by addressing the root causes of zoonotic emergence and spread.

Our appetite for meat has brought us in ever-closer contact with both domesticated and wild animals – by keeping ever more of them in ever more confined spaces, and invading ever more of their habitats. Together with the human-made modification of the environment, this has helped the number of emerging zoonotic diseases to increase.123 Or – to put it differently – many of today’s contagious diseases are a problem of our own making. We have literally eaten our way to zoonoses. Today, livestock accounts for 60% of all mammal biomass on the planet (with wild mammals accounting for only 4% and most of the rest attributed to humans), while poultry accounts for 70% of bird biomass, 4marking a major human-made transformation in the species composition of our planet.

ZOONOSES – EMERGENCE AND PREVALENCE

It is not uncommon for viruses to spread from animals to humans, as it is in their nature to find new hosts. Animal species can become reservoir hosts for pathogens, maintaining them permanently, without the host necessarily showing symptoms but still able to spread it to other individuals, populations, or species that then might show symptoms. Other pathogens are actively spread via vectors such as ticks or mosquitoes which bite their hosts, thus spreading vector-borne diseases such as malaria.

Despite the ubiquity of viruses on the planet, zoonotic spillovers seem to be quite rare. It is thought that there are between 260,000 and more than 1.5 million viruses that have their origin in mammals and birds.56 Of these, only 219 viruses have thus far been shown to infect humans.7 Nonetheless, about 75% of all emerging infectious diseases that affect humans are zoonoses. In other words, when we are confronted with new communicable diseases, three out of four times they originated in, and have been transmitted to us by, wild or farmed animals 8910111213 – with potentially serious consequences, as past outbreaks have demonstrated.

Some of the most well-known zoonotic diseases include SARS, MERS, Ebola, rabies, and certain forms of influenza. Whether originating in wild animals, as is assumed with COVID-19, or in farmed animals, as is the case with avian and swine flu, they all pose serious threats to individual and global health – with some of them being potentially far more severe and deadly than COVID-19. Increasing incidents of human-animal interaction and contact points (such as humans expanding into natural areas or high-density farming) increase the risk of zoonotic events.

Not every zoonotic disease develops into a pandemic of COVID-19-like proportions. And they don’t need to in order to pose a serious threat to humans. But, even without turning into acute pandemics, zoonoses are still responsible for about 2.5 billion cases of illness and 2.7 million human deaths worldwide, every single year.14 To put these figures into perspective: in 2017, traffic accidents caused 1.24 million deaths and diabetes caused 1.37 million deaths globally.15 So, regular, non-pandemic zoonoses cause far more harm than all traffic and diabetes fatalities around the world, combined. Even non-fatal zoonoses cause massive damage to human health, societies, and economies, given that one out of four people on this planet is affected by a zoonotic disease – annually.

In today’s globalised world, international travel and trade have become an hitherto unparalleled accelerator for spreading pandemic diseases around the globe within a matter of days. There is substantial evidence that outbreaks of animal-borne and other infectious diseases are on the rise.16 The World Health Organization (WHO) tracked about 1,500 epidemic events in 172 countries during the period between 2011 and 2018,17 and it is highly likely that the current coronavirus crisis is only a forewarning of what is yet to come. Epidemiologists are waiting for the ‘big one’ – not if but when. Many experts had in fact warned about the risk of a new coronavirus causing a pandemic 18192021 – which is exactly what happened.

THE COVID-19 PANDEMIC – (ONE STEP CLOSER TO) THE BIG ONE?

According to a report by the Global Preparedness Monitoring Board, co-convened by WHO and the World Bank, and published in September 2019, “the world is at acute risk for devastating regional or global disease epidemics or pandemics that not only cause loss of life but upend economies and create social chaos.”22 Just a few months later, the world witnessed this prediction materialise. Whether the current COVID-19 pandemic is in fact ‘the big one’ is yet to be seen. However, it is already quite clear that the world has never before experienced a pandemic that has spread so rapidly, affecting virtually every human on the planet, and representing an unprecedented crisis. Those who are not infected with the virus itself are impacted by governmental regulations aimed at limiting its spread, such as nationwide lockdowns, strict social distancing, and international travel bans – affecting all aspects of social, political, and economic life and daily routine, resulting in social and economic hardship.

PUTTING COVID-19’S CASE-FATALITY RATE INTO CONTEXT

When it comes to assessing the hazard posed by a virus, the most widely used measure is the case-fatality rate. While the impact of COVID-19 is unparalleled in modern times, it is not nearly as deadly as some other zoonotic diseases. Although the actual case-fatality rate is still under debate, the case-fatality rate varies greatly according to region, with a current average of 4.7% (as of 5 July 2020).23 This makes COVID-19 substantially more dangerous than regular flu, which has a case-fatality rate of less than 0.1%.24

 

Its case-fatality rate, however, is dwarfed dramatically by that of, say, avian flu and its variants, with rates of up to 60% (H5N1)25 or, potentially, up to 90% in the case of Ebola.26 If one of these zoonoses turns into a pandemic, the consequences on health, healthcare systems, societies, and economies are difficult to imagine, and most aspects of human social organisation are likely to collapse. Even with COVID-19’s relatively low case-fatality rate, healthcare systems are already experiencing serious strain – despite the massive political and social containment measures that have been put in place. If the case-fatality rate of a future global zoonotic outbreak is similar to those of Ebola, H5N1, or the 1918 flu pandemic, its effects will certainly overwhelm virtually all existing infrastructure. It will no longer be a question of enough ventilators and intensive care capacities – but of enough doctors and nurses still able to do their jobs.

 

Not only might future outbreaks be more dangerous, experts agree that they are also expected to be more frequent.2728 The potential causes behind this alarming forecast are human-made – and the most central human activities in this context are all related to our global food system. 

Food & Pandemics Report

By exploring the crucial connection between the current crisis and our animal-based food system, the ProVeg Food & Pandemics Report highlights how our food choices help to create a recipe for zoonotic pandemics.

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References

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