The Black Death 1346-1353: The Complete History

Port cities acted as epicenters for the Black Death’s transmission in medieval Europe. These epicenters were infected through shipping connections with Eurasia as Italian merchants fled Kaffa. Although the plague also traveled over land, ships were the primary vehicles of transport, allowing the Black Death to make numerous metastatic leaps, as it did when it entered Weymouth in England by ship from France and then jumped to Norway through the grain trade that departed Weymouth. These leaps “greatly hastened the Black Death’s conquest of Europe, and, arguably, made the almost total success of the European campaign possible” (231). The average rate of transport by ship was 40 kilometers per day, while overland plague traveled roughly two kilometers per day. Thus, the plague had the ability to travel more swiftly by sea. Furthermore, the slow pace at which the plague spread by land, according to the epidemiological evidence outlined above, confirms that the Black Death was bubonic, not pneumonic, plague because the latter would have spread more swiftly.

Pace of spread and population density also interacted to affect the dynamics of plague’s spread. As the author notes, “high population density […] increased the pace of spread along communication lines,” but it also “slowed down the pace of conquest” (231) due to the time required for the illness to reach epidemic levels in a larger population. For example, the plague arrived in Norway in the late autumn of 1349 and attacked on two fronts, with the first epicenter at Oslo. From Oslo, plague began its spread the following April. The country was fully contaminated within the year. Conversely, the plague’s spread in Denmark was much slower due to its greater population density. A similar pattern occurred in densely populated Italy and France. The plague arrived in Italy as early as 1347 but did not fully consume the region until 1350.

The plague’s seasonality also provides information on how it propagated and suggests that the Black Death was dominated by the bubonic variety of plague. Patterns of spread in Europe show that the Black Death slowed—or even vanished—in the winter, and its spread slowed in cooler, mountainous areas. For example, in northeastern France, the plague’s spread over land between the towns of Besançon and Chalon was approximately 1.1 km per day but in the winter slowed to 0.4 km between Besançon and Montbéliard. Likewise, although the Black Death appeared in Austria by 1348, it was unable to cross the mountains into Bavaria until the spring of 1349. Pneumonic plague is transmitted from one person to another by respiratory droplets in the air, so that it is not driven by temperature.

Although it was not impossible for cases of plague to appear in winter, it was less common for them to do so. The plague’s winter crawl, therefore, suggests that the bubonic version dominated the pandemic of the mid-1300s. Bubonic plague, spread by fleas, “requires a climate with moderately warm temperatures that promote the procreation of fleas and the reproduction of the flea population” (235). Although primary source descriptions of the Black Death suggest that it may have been both bubonic and pneumonic plague, these descriptions make clear, based on the symptoms, that these victims suffered from secondary—not primary—pneumonic plague, which follows the bubonic infection. Indeed, “secondary pneumonic plague is a normal feature of bubonic plague epidemics, comprising 10-25 per cent of all cases” (238).