Plague doctor, healer of the plague and lost souls... There are several reasons for the emergence of the bubonic plague, also known as the Black Death. These include global cooling, wars, dense populations, poor personal hygiene, and unsanitary streets. One of the most important factors was the mass extermination of cats. For religious reasons, cats were considered witches' companions and, in general, the devil's pet. But fewer cats meant more rats. And rats were the main carriers of the bubonic plague. Jews were also blamed for the spread of the plague. People believed they were poisoning wells. They were treated the same way as witches and cats. But even this didn't help. Meanwhile, the plague continued to spread. Medicine at the time was powerless, unable to find the cause of the disease or prevent it. It is estimated that the Black Death claimed approximately 40 million lives.