ABSTRACT
How does something new spread through society, from one person to the next? A closer look at the outbreak and spread of diseases may be somewhat unpleasant, but it is very instructive. e Bubonic Plague (aka the Black Death) struck Europe in the 14th century. Responsible for this horrible, deadly disease was probably the bacterium Yersinia pestis, transmitted by ea bites. e bacterium originated in Asia and reached European seaports in the 14th century (note that by then the plague had already wiped out large parts of the populations of China, India, Syria, Mesopotamia and Armenia). e story goes that in 1347 the trading city of Caa in Crimea was under siege by the Mongol Army. Aer it became clear that the city was almost undefeatable, the besiegers decided to catapult the corpses of people who had died from the plague into the city. In the face of this, traders from southern Italy immediately ed by ship – and, unknowingly, took the plague with them to Sicily, from where it spread in no time all over Europe, leading to an appalling death toll of 75-200 million people across Europe and Asia within a few years. In some macabre sense, we can call this a very successful disease. Compare this to the current outbreak of Ebola in parts of Africa. Again, this is a horrible, deadly disease, caused by the Ebola virus and at least as infectious as the plague. But while the number of fatalities in the aected areas is still tragically high (there are about 12,000 reported fatalities so far), it does not reach the magnitude of the plague, and the disease has not yet spread widely beyond these regions. ere is even a good chance that it will be controlled in the very near future. So, in some sense, we can call this a failed disease.
