Clement VI was on the papal throne when the Black Death first struck Europe in 1347. This pandemic swept through Asia and the Middle East and into Europe between 1347 and 1350, and is believed to have killed between a third and two-thirds of Europe's population. During the plague, Clement attributed the plague to divine wrath. But he also sought the opinions of astrologers for an explanation. Johannes de Muris was among the team "of three who drew up a treatise explaining the plague of 1348 by the conjunction of Saturn, Jupiter, and Mars in 1341" Clement VI's physicians advised him that surrounding himself with torches would block the plague. However, he soon became skeptical of this recommendation and stayed in Avignon supervising sick care, burials, and the pastoral care of the dying. He never contracted the disease, even though there was so much death around him that the cities ran out of ground for cemeteries, and he had to consecrate the entire Rhône River so that it could be considered holy ground and bodies could be thrown into it. One of Pope Clement's physicians, Gui de Chauliac, later wrote a book called the "Chirurgia magna" (1363), in which he correctly distinguished between bubonic and pneumonic plague, based on his own observations of his patients and himself.