Book Excerpts

Armies of Pestilence

An absorbing and accessible account of the effects of disease and pandemics on human history, from the ancient to the modern world.

From R.S. Bray, Introduction, Armies of Pestilence (Cambridge: The Lutterworth Press: 2020), pp.11 Order now for a 15% discount.

Of all the human diseases which will be considered in this book only one thought to be as old as man — malaria. Parasites occur in the blood of chimpanzees and gorillas which are virtually indistinguishable from those causing malaria in people. It must be assumed therefore that we acquired malaria parasites from our ape ancestors at the time when our stock separated away from the higher ape stock.

All the other epidemic diseases considered here, plague, cholera, smallpox, typhus, yellow fever and influenza, are thought to be late-comers to the bodies of people and are the result of certain critical numbers of people coming together. Informed opinion has it that these great pandemic diseases (malaria is usually endemic) require a certain amount of crowding of people before they can achieve an epidemic state.

So it is usually claimed, with justice, that while man was a widely scattered hunter-gathered he was free of the major communicable diseases other than malaria. When man became an agriculturalist and pastoralist and collect together in groups he became prey to infectious diseases.

The other general remark, which can be made at this point, is that all of these diseases were to begin with, zoonotic; that is to say they commence as diseases of animals and were transmitted from those animals to man. Subsequently most were transmitted from man to man, losing the original animal reservoir from their life-cycle. It is generally assumed that continuing zoonoses are by nature endemic, that is only sporadically distributed and of medium to low incidence in the human population as they are transmitted to man only occasionally even if constantly. Thus yellow fever transmited from monkeys to people will give rise to only sporadic disease in man. Yellow fever only becomes epidemic when it is transmitted from man to man by local mosquitoes. Medical biology has not yet reached the state of exact laws perceived and proclaimed by man so any general statement made here is subject to exceptions and in science the exception does not prove the rule in the sense of confirming it; on the contrary it disproves the rule.

Arising out of what has just been said about zoonoses the great surprise is that pandemic plague should have been a zoonosis involving the rat as it was found to be in late nineteenth and early twentieth century pandemic. The surprise is so great that doubt should be cast on the supposition that all plague pandemics must have been bubonic plague exclusively and this question will be discussed in greater detail later.

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