Covid-19, Ebola, HIV, SARS, TB, Zika, even the Black Death – what do these diseases all have in common?
They are all zoonotic diseases – infectious diseases caused by the transfer of bacteria, viruses or parasites from animals into humans.
These diseases often make the jump from other mammals and in some cases can come via intermediate ‘vector’ species. The list is long and includes some of the most ruthless killers in the world – in fact more than 2.5 billion cases of illness and 2.7 million deaths every year are down to zoonotic diseases.
Crucially, although zoonotic diseases account for 60% of known infectious diseases, over 75% of new or emerging infectious diseases are zoonotic in origin. And while zoonotic diseases lead to 15.8% of deaths globally, they account for 43.7% of all deaths in low resource countries, and so have an even greater impact amongst the world’s poorest people.
It is perhaps no surprise then that many zoonotic diseases in history have emerged in China. From the Black Death itself (which killed an estimated 75-100 million people) through to coronavirus today, many pandemics have emerged from Chinese ‘wet markets’ where numerous animal species are kept in close captivity, leading to an increased probability of vector-based transmission. The fact that wild creatures such as bats, sometimes seen as a delicacy but known to carry many deadly pathogens, are on sale in these markets only exacerbates this issue.
But we can’t point the finger at China alone; in Africa the consumption of bush meat and mixing of various creatures is thought to have led to SIV or the Simian form of HIV to make the jump from monkeys to humans, with a similar pathway likely behind Ebola and Zika. And Spanish Flu, the early 20th Century killer that led to more deaths than the World Wars combined, is thought to have originated on the Western Front where various farm animals were kept as food supplies in highly unhygienic conditions.
There are also three trends which mean that even common, domesticated farm animals could help bring about the next deadly pandemic: firstly, factory farming means animals are held in ever closer captivity; secondly, the huge amounts of antibiotics given to animals to help them survive such confined conditions; and thirdly, increasing deforestation and habitat destruction for farming is bringing us in closer contact with wild animals.
For a demonstration of the impact of modern farming methods, consider that a chicken today weighs four times what it would have 60 years ago. That’s a result of factory farming methods, including the increased use of antibiotics. Indeed, over 70% of all antimicrobials used in the USA are used not for humans, but for livestock. This makes factory farming sites ideal breeding grounds for new pathogens that are not only zoonotic, but also resistant to antibiotics, making them potentially lethal to humans.
This is why the deadliest epidemics of this century before Covid-19 – the 2009 swine flu epidemic, and the H3N2 US flu epidemic – both emerged via common farm animals. In fact the 2009 swine flu epidemic still remains the deadliest, with up to 575,000 deaths worldwide. It was also the second pandemic to involve the H1N1 influenza virus after Spanish Flu.
Coronavirus may therefore prove to be a warning shot and simply a sign of things to come. Although Covid-19 is ten times deadlier than seasonal flu, its case fatality rate or CFR is probably close to 1%, based on data from the only controlled study known to us at this time – the Diamond Princess cruise ship. To put this into perspective, tuberculosis has a CFR of 15% and Ebola 50%.
A future zoonotic disease with a CFR even a couple of points higher could be impossible for us to contain. After all, Spanish flu, which killed tens of millions in just two years, only had a CFR of 2%.
There is of course a simple solution to avoid such a catastrophe – that we as humanity decide to no longer consume animal products. Zoonotic diseases are a threat because the pathogens involved are made of proteins that are able to bind to human receptors. Plant-based pathogens on the other hand cannot affect us in this way. There will never be a carrot flu or a lentil flu.
Clearly, it would be impossible to achieve such a dramatic change overnight. But there are a number of intermediate steps we can take towards a plant-based future, which will also protect us against future zoonotic strains.
Firstly, we must all cut down our meat consumption and treat it as a luxury like our ancestors did. Not only is this better for our health and well-being, it is also the most effective way in which we can reverse factory farming trends focussed on increasing livestock yields at any cost. Thankfully, plant-based alternatives to meat are already coming on in leaps and bounds, with familiar high street names such as Gregg’s and Burger King now selling meat-free versions of their signature products.
Secondly, the consumption of wild animal meat needs to be urgently addressed. That will require a combination of individual government action and international cooperation. The ban on wildlife markets in China is a welcome first step, though evidence on the ground suggests it isn’t yet being fully enforced. Strengthening global agreements such as CITES, which has long been flouted, could be crucial in protecting wild species if there is enough will and pressure from both public and politicians.
Finally, and most important of all, we need greater awareness and a frank discussion of the threat posed by factory farming and zoonotic diseases. We often brush the impact of meat and dairy consumption under the carpet. Yet the clear links it has to both climate change and zoonotic diseases are now too important to ignore. It is time therefore that we all – individuals, politicians and the media – are clear and honest about the true impact of what we eat.
Though the objective of not eating animal products is simple enough, the steps to get there are obviously pretty drastic. Nonetheless, they still represent the most straightforward way to safeguard humanity from a future zoonotic pandemic that could be even more deadly than Covid-19.
Let’s all go vegan – before it’s too late.
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