Transmission and Mortality

There is considerable debate over the ways in which the Black Death was transmitted from person to person and place to place. Plague is an ecologically complex disease, depending on the mutual interaction of bacilli, rodents, fleas, and humans; the lack of detailed evidence about the experience and behavior of animals and insects in the mid-fourteenth century forces us to rely on indirect and therefore ambiguous evidence derived from the speed and pattern of the epidemic's spread.

The disease was clearly propagated by humans; rather than moving slowly across fields and forests from one group of rodents to another, it progressed quickly along major routes of trade and communication, traveling faster by sea than by land. Thus in virtually every area in which its trajectory is known (the Black Sea, the Mediterranean, the North Sea, the Baltic), it appeared first in ports and then spread more slowly along roads and rivers to inland cities and from there into the surrounding countryside. A number of extremely remote areas, including parts of the Pyrenees, the central Balkans, and the sub-Atlas region, seem to have escaped largely or entirely.

Historians differ, however, about the ways in which humans acted to spread the plague. Virtually all agree that ships carried colonies of diseased ro dents from port to port, where they could infect the local rat population, and that sick rats also traveled overland hidden in shipments of cloth and grain. Some also emphasize the autonomous role of the oriental rat flea, Xenopsylla cheopis, which could survive independently and be transported in cloth and bedding. Others add to that the role of the human flea, Pulex irritans, arguing that in severe epidemics such as the Black Death with a high incidence of septicemic plague, fleas could transmit the disease between humans with no need for a rodent intermediary (Biraben 1975; Ell 1980). In addition, on the basis of detailed contemporary descriptions, it is now almost universally accepted that in both Europe and the Middle East, the Black Death also included numerous pockets of primary pneumonic plague, a highly contagious airborne disease. It seems likely that all of these forms of transmission were involved, although their relative importance varied according to local conditions.

It is difficult to judge mortality rates during the Black Death with any precision, except in a few areas. Contemporary chroniclers tended to give impossibly high estimates, whereas other records-necrologies, testaments, hearth taxes, and so forth -are incomplete or reflect only the experience of particular groups or require extensive interpretation. Nonetheless, historians generally agree that death rates most commonly ranged between about 30 and 50 percent in both Europe and the Middle East, with the best records indicating a mortality in the upper end of that range. Some areas are known to have suffered more than others. It is frequently claimed that central Italy, southern France, East Anglia, and Scandinavia were most severely affected, although the evidence for this claim is uneven. Clearly, however, certain regions were relatively fortunate; Milan, for example, Bohemia, and parts of the Low Countries seem to have experienced losses of less than 20 percent, whereas Nuremberg, for some reason, escaped entirely. In general, however, the trend in recent research is to move the estimated mortality rates upward. It now appears that many remote and rural areas suffered as much as the larger cities and that a number of regions previously thought largely to have escaped the epidemic, such as parts of the Low Countries, were in fact clearly affected. The Black Death seems to have been more universal and more virulent than many historians a generation ago believed.

Some groups also suffered more than others, even within a single city or region. A number of contemporary observers in various parts of Europe corn-

mented on the relatively high death rates among the poor. These assertions are plausible; the poor lived in crowded and flimsy houses, which would have allowed the easy transmission of plague from rats to humans and from person to person, and they did not have the luxury of fleeing, like the rich, to plague-free areas or to their country estates. Conversely, death rates seem to have been somewhat lower than average among the high European aristocracy and royalty, who lived in stone buildings and were relatively mobile. People whose occupations brought them into contact with the sick, such as doctors, notaries, and hospital nurses, appear to have suffered disproportionately, at least in some areas, as did people who lived in large communal institutions, such as the Mamluks of Egypt and Syria or members of Christian religious orders. For all these groups, the main factor seems to have been increased exposure rather than susceptibility.

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