7 - The Disease Pattern

Summary

The ecological revolution influenced not only the landscape and the social structure but also the world that is only visible under a microscope, the infinite microworld of bacteria and parasites. Some of the diseases that had terrorized the population for centuries disappeared – plague was one of these. Others were forced back; malaria, for example, which by the year 1800 was on its way out of the disease pattern. On the other hand, tuberculosis emerged from relative obscurity and was ready to assume the role of great killer as soon as the last remaining competitor, smallpox, had been eliminated; after a long preliminary attempt, this was finally achieved just after 1800. The nineteenth century became the century of tuberculosis.

PLAGUE

Plague is caused by the bacillus Pasteurella pestis. Pasteurella pestis has its ecological basis far from human beings, both geographically and biologically, and comes into contact with them only in exceptional circumstances. A modus vivendi has never been established between human beings and the plague bacillus as it has with most of the other infectious diseases, AIDS being the latest and perhaps most important exception. This explains the violence with which plague attacks, and still attacks, when it goes astray amongst human beings, as occasionally happens, for example, in the western United States and in parts of the former Soviet Union.

The plague bacillus has its focus, or permanent base, amongst burrow-dwelling rodents such as squirrels and beavers.