Objectives: In this study, we aimed to investigate the effects of malaria on the lives of Roman pontiffs.
Materials and methods: The histories of all 264 popes from Saint Peter to John Paul II were extensively studied.
Results: Malaria affected the lives of Roman pontiffs. Between 999 AD and 1644 AD, 21 of 99 popes were affected by malaria (21.4%). The first affected was Gregory V and the last was Urban VII, the 138th and the 235th pope, respectively. There were 15 deaths (15.2%). Six pontiffs (6.1%) were infected but survived. Many cardinals and their assistants, especially those coming from northern countries, contracted malaria during conclaves, and many died.
Conclusions: By about 450 BC, malaria had arrived in Rome. By the second century BC, malaria was endemic. It affected the lives of Roman people. To prevent infection, the popes adopted the custom of ancient affluent Romans who used to spend summer months in high plains far from Rome. The first to adopt the custom was Paul I in 767, who just moved his residence to Saint Paul, out of the walls. Sixtus V started the Congregation of Waters and Streets, which was routinely reinforced by his successors until 1860, when the Kingdom of Italy was born.