The Black Death swept across Europe between 1347 and 1353, killing millions. Then the outbreak of plague continued in Europe until the nineteenth century.
One of the most popular facts about the plague in Europe is that it was spread by rats. In some parts of the world, the bacteria that cause plague, Yersinia pestisMaintains for the long term Presence of wild rodents and fleas. This is called the animal “repository”.
While the plague begins in rodents, it is sometimes transmitted to humans. Europe may once have hosted animal reservoirs that caused epidemics of the plague. But the plague could also have spread again and again from Asia. Which of these scenarios was present remains a matter of scholarly debate.
our recent search, Posted in Proceedings of the National Academy of Sciences (PNAS), showed that environmental conditions in Europe would have prevented the plague from surviving in stable, long-term animal reservoirs. How, then, did the plague persist in Europe for so long?
Our study presents two possibilities. First, the plague was being reintroduced from Asian reservoirs. Secondly, there may have been temporary short- or medium-term tanks in Europe. In addition, the two scenarios may be mutually supportive.
However, the rapid spread of the Black Death and subsequent outbreaks in the next few centuries also suggests that slow-moving rats may not have played the critical role in transmitting the disease they are often portrayed.
To find out whether plague could survive in long-term animal tanks in Europe, we examined factors such as soil properties, climatic conditions, terrain types, and rodent species. All of these factors seem to affect the ability of plague to survive in reservoirs.
For example, higher concentrations of certain elements in the soil, including copper, iron, and magnesium, as well as higher soil pH (whether acidic or alkaline), cooler temperatures, higher elevations, and lower precipitation appear to develop Fixed cabinets, though it’s not entirely clear why, at this point.
Based on our comparative analysis, centuries-old plague reservoirs of wild rodents were less likely to have existed from the Black Death of 1348 to the early 19th century than they are today, when extensively researched It excludes any such reservoirs within Europe.
This contrasts sharply with regions across China and the western United States, where All of the above conditions to insist Yersinia pestis Reservoirs are found in wild rodents.
In Central Asia, long-term, continuous rodent tanks may have existed for thousands of years. Ancient DNA and textual evidence also hintsOnce the plague crossed into Europe from Central Asia, it appears to have sowed short- or medium-term sows or reservoirs in European wild rodents. The most likely place for this was in Central Europe.
However, since the local soil and climatic conditions do not favor long-term and continuous reservoirs, the disease had to be re-imported, At least in some cases. Importantly, the two scenarios are not mutually exclusive.
To delve deeper into the role of rats in spreading the plague in Europe, we can compare different outbreaks of the disease.
The first plague pandemic It began in the early sixth century and continued until the late eighth century. The second pandemic (which included the Black Death) began in the 1330s and lasted five centuries. A third pandemic began in 1894 and is still with us today in places like Madagascar and California.
These epidemics largely included the bubonic form of the plague, in which the bacteria infect the human lymphatic system (which is part of the body’s immune defences). In pneumonic plague, the bacteria infect the lungs.
Epidemics of the second pandemic differed radically in their nature and transmission from modern epidemics. First, there were strikingly different levels of mortality, with some second epidemic outbreaks reaching 50 percent, while third epidemic outbreaks rarely exceeding 1 percent. In Europe, the numbers for the third pandemic were even lower.
Second, there were different rates and patterns of transmission between these two eras of plague. There were huge differences in the pace and speed of moving goods, animals, and people between the late Middle Ages and today (or the late nineteenth century). However, the Black Death and many of its subsequent waves spread with astonishing speed. above the ground , He raced fast almost every day As do recent outbreaks of the disease over the course of a year.
As described by contemporary historians, physicians, and others—and as quantitatively reconstructed from archival documents—the epidemics of the second pandemic It spread faster and more widely than any other disease during the Middle Ages. In fact they were faster than any period even Cholera outbreaks from 1830 or major influenza in 1918-2020.
No matter how the various European waves of the second pandemic begin, wild and non-wild rodents — rats, first of all — move much more slowly than they move around the continent.
Third, the seasonality of plague also shows wide variations. Third pandemic epidemics (except in rare cases, mainly pneumonic plague) followed the fertility cycles of rat fleas. These rise in relatively humid conditions (although low rainfall is important for the establishment of plague reservoirs for the first time) and within Temperature range between 10°C and 25°C (50 to 77°F).
By contrast, second pandemic epidemics can cross the winter months in bubonic form, as was seen across the Baltic regions from 1709-13. But in a Mediterranean climate, from 1348 until the 15th century the plague was a summer infection, peaking in June or July – during the hottest and driest months.
This deviates strikingly from the plague seasons in these areas in the twentieth century. Because of the low relative humidity and high temperatures, these months were the times least likely for plague to spread among rats or humans.
These differences raise the crucial question of whether the bubonic form of plague relied on slow-moving rodents for transmission when it could instead It spreads most efficiently directly, from person to person. Scientists have speculated that this may be caused by external parasites (fleas and possibly lice), or through people’s breathing systems and through touch.
Questions such as the exact roles humans and rats played in previous plague epidemics need more work to be resolved. But as this study and others have shown, great strides forward can be made when scholars and historians work together.