The Source of New Infectious Diseases

This seems like a timely question, in the light of the current Covid-19 outbreak. Everyone knows how you get an infectious disease: you get it from another person who has it. But where did the first person get it? And if they just evolve in the same way that animals and plants evolve, shouldn’t it take really long for new diseases to appear?

In my lifetime, the following new diseases have appeared, just off the top of my head: Covid-19, SARS, Mad Cow Disease, Swine Flu, and AIDS. The last of these has killed tens of millions of people. There will certainly be more such diseases appearing over the next few decades, and we never know when a more deadly, more contagious one will appear. Think about what would happen if there was a disease as deadly as AIDS and as contagious as Covid 19. I think there is a non-negligible chance that this is how the human species will finally end.

Where do these things come from? The answer is well-known, but on the chance that you don’t know about it or (more likely) just haven’t thought about it, the main answer is animals. Those diseases all started out as non-human animal diseases. Apart from SARS, they were transmitted to the human species through a human being eating body parts from an infected animal. Covid-19 probably came from eating pangolin meat, mad cow of course from cows, swine flu from pigs, and AIDS from chimpanzees and monkeys (which were hunted for meat in Africa). The disease enters a human population through a meat-eater, mutates (except Mad Cow, which is a prion disease, not a virus), then spreads from there.

The Moral Problem

So that’s another reason to end the meat industry (besides the severe cruelty of that industry). Of course, when you eat some meat, under normal conditions, you only have a tiny chance of getting a disease from that, let alone a new disease. But, in the extremely unlikely event that you do get a new disease, you create a worldwide threat, and one that may threaten people for generations to come. In the age of globalization, any new communicable disease is in danger of spreading across the world.

Notice also that the risk is not merely assumed by meat-eaters. Once one of these diseases migrates to a human host, it will mutate to become a human disease, and then spread through human-human contact. So everyone who has contact with other humans, whether they are carnivores or vegetarians, is put in danger from this sort of thing.

I think there is a plausible case that this makes meat-eating a rights-violation — not just a violation of animal rights, but a violation of human rights. The meat eaters of the world violate the rights of vegetarians by subjecting us to an unnecessary risk of disease for no good reason.

The Ethics of Risk

Certainly, if you knew that you were going to transmit a deadly disease to other people, and you did so anyway, just to gain a little pleasure for yourself, this would be a rights violation. But you might think it isn’t a rights-violation if there is only a small chance of this.

Sometimes, it’s permissible to impose a small risk of harm on others, and sometimes it isn’t. It matters (a) how big the harm would be, (b) how likely it is, and (c) how good your reason for imposing the risk is. Some examples:

(Illustrating (a), Size of Harm): It’s ok to keep a gun in your house, but not ok to keep a nuclear bomb, even if (let’s suppose) the probability of a nuclear bomb accident is much less than the probability of a gun accident.

((b), Probability): It’s permissible to drive normally, but not permissible to drive while drunk.

((c), Quality of Reason): It’s not permissible to play Russian roulette, for fun, with unwilling other people. Even if your revolver has 1,000 chambers (giving only a 1/1000 chance of killing someone), it is still not okay. Nor is it ok with a million chambers, or a billion. No number of chambers is okay.

I just assume those judgments. I’m not going to argue for them. Those examples illustrate the relevance of factors (a), (b), and (c) above.

How does the meat industry fare? Any given meat company or consumer has only a tiny chance of introducing a new disease to humanity, so they’re doing well on (b). However, there is a potential for extremely large harm, so they’re doing poorly on (a). Unfortunately, we have no good estimates of the expected harm.

Finally, meat producers and consumers are doing extremely poorly on (c) — overall, they have extremely poor reasons for selling or eating meat. Note: I take it that, for purposes of assessing the quality of one’s “reason” for imposing a given risk, we look at one’s overall, net reason, omitting the possible moral reason created by the very risk we’re talking about. (That’s to avoid circularity or double counting.)

So, leaving aside the disease risk, how good of a reason do we have for selling or eating meat? Overall, extremely poor — we get some increase in gustatory pleasure, we also get increased risk of cardiovascular disease and cancer, and we cause a vast quantity of suffering for other sentient beings that is orders of magnitude greater than that increase in pleasure that we get. So the overall reason for doing it (leaving aside the disease risk) is less than zero. See my book on vegetarianism: https://www.amazon.com/dp/1138328294/.

So the risk isn’t justified. It’s like the Russian Roulette case, only worse. In the Roulette case, you merely have no reason to do it, considered apart from the shooting risk; in the meat case, you have overall extremely powerful reason not to do it, considered apart from the disease risk.

What if you think, for some reason, that vast quantities of pain and suffering for other creatures are not a reason against meat-production? (Many people appear to assume this, though no one has been able to give any non-absurd defense of this. Again, see my Dialogues on vegetarianism.) Even so, the overall reason you have to eat meat would still be dubious, since it’s not even clear that you are overall better off. There is a reasonable argument that you’re overall worse off due to health effects. (See https://well.blogs.nytimes.com/2011/01/07/nutrition-advice-from-the-china-study/.)

Btw, this moral reason against meat-production applies even to humanely-raised meat (if such there be).

I discuss this and other arguments in this online discussion (with Aeon Skoble, Andy Lamey, and Shawn Klein): https://www.cato-unbound.org/issues/february-2020/what-do-humans-owe-animals.