Temperature, toponyms and thresholds: A modelling approach to understanding the spread of plague during the second pandemic

Plague is a disease of rodents and is transmitted through their fleas. Humans are only occasionally infected. Direct human-to-human transmission through droplets happens rarely. The low plague activity in humans nowadays contrasts the millions of casualties during the second pandemic (14th-18th century), and the circumstances of historical outbreaks are poorly understood. In her PhD thesis, Fabienne Krauer has studied drivers and mechanisms that could explain the spread of plague during the second pandemic in Europe and the Mediterranean. Krauer first shows that historical outbreaks followed a distinct seasonal pattern and occurred within a specific temperature range. Krauer then models the temperature-dependent seasonality of the human flea as a potential plague vector, and shows that the flea seasonality correlated with the observed plague seasonality. Moreover, Krauer explores the contribution of pneumonic transmission in addition to human flea transmission with a mathematical model. Her results confirm that the life cycle of the human flea could explain the seasonality of historical outbreaks. Finally, Krauer studies the performance of natural language processing to facilitate the digitization of plague data and presents two novel, geocoded datasets of plague outbreaks in Eurasia. Overall, this thesis provides insight into the complex relationship of vectors, climate and disease