Black Death

This name is given to the pandemic bubonic and pneumonic plague that swept across the Middle East, the Mediterranean region, and Europe in the fourteenth century. Great epidemics had occurred before, but never with the ferocity of the Black Death. It seems to have begun in Asia Minor in 1345 or 1346 (although there may have been earlier outbreaks farther east in what is now Iran, and there were a large epidemic around this time in China). The incessant wars and failed harvests of those times encouraged turbulent population movement, and food shortages bordering on famine sapped resistance to contagious disease, thus aggravating the severity of the epidemic. It was the first great pandemic of recorded history, with death rates reaching and in places exceeding 70 percent. The plague spread along trade routes as well as in battle fields. In 1347 it reached Naples and Genoa, and from there it rapidly spread across western Europe, striking heavily populated cities, such as Vienna and Paris, and isolated rural villages alike. The Black Death caused large painful swellings to appear in the groins and armpits and black blotches on the skin due to blood leaking from the veins. Fever, delirium, and death followed in short order. The dramatic and sudden onset, rapid course, and terrible aspect evoked horror and fear, leading many who came in contact with it to fleend as they were contagious contacts, they aggravated the further spread of the disease. The terrifying onslaught of the Black Death in an era of superstition was explained as the wrath of God or relief was sought by seeking scapegoats. Jews, witches, and others were burned at the stake.

There has been considerable debate about the nature of the Black Death. Was it due only to the plague bacillus, Yersinia pestis, to this and other conditions such as overwhelming streptococcal and/or staphylococcal infections that coexisted, or could it have been due to anthrax? There are reliable clinical descriptions, though there is much folklore from which inferences can be made. The ecology of plague is complex: Yersinia pestis may be transmitted by direct contact or a droplet spread from infected to susceptible persons, but bubonic plague typically is a zoonosis, a disease of rodents, especially rats, transmitted by the rat flea. It spreads from rats to humans in rat-infested dwellings. There is good historical evidence on the prevalence in those days of black rats, Rattus rattus, which prefer indoor habitat and nesting sites close to where people live. Over the next one hundred to two hundred years, black rats were supplanted by brown rats, Rattus norvegicus, whose preferred habitat is outdoors, removing them and their fleas to a slightly safer distance from people.

The Black Death waned slowly, and smaller localized epidemics broke out over the centuries that followed. The waning of the pandemic was due to several factors: extermination of susceptibles, leaving resistant survivors alive (blood group frequencies and other genetic markers are evidence of this); displacement of black rats by brown; and ecosystem changes (the use of brick and stone reduced indoor nesting sites for rats).

JOHN M. LAST

(SEE ALSO: Epidemics; Plague)