At the onset of the French Revolution in 1789, a wave of panic known as the ‘Great Fear’ spread through the population like a virus, moving along the road network at an average speed of 45 kilometres per day and disproportionately affecting the wealthier and more literate areas of the country. This finding is based on epidemiological models, typically used to study disease propagation, which researchers from the University of Milan applied to this historic social phenomenon in collaboration with the Université Paris 8 and the University of Toulon. The results, which are also useful for deciphering modern phenomena like the spread of fake news, are published in the journal *Nature*.
The study meticulously reconstructs the spread of the Great Fear between July 20 and August 6, 1789, a period when an uncontrollable wave of rumours about armed bands and aristocratic conspiracies to suppress the Revolution swept across France. This panic fueled peasant revolts against landowners and the destruction of feudal documents—events that prompted the National Assembly to announce the abolition of feudal privileges on August 4.
By cross-referencing historical sources, ancient maps, and contemporary demographic and socioeconomic data—such as grain prices, literacy rates, and land ownership—the researchers employed an innovative approach based on epidemiological models. They discovered the Great Fear propagated through the road system in a pattern similar to a virus, peaking on July 30, 1789. The team calculated that the rumours advanced at an average speed of 45 kilometres per day from village to village, with 40% of the affected locations found near a postal relay station. Areas with higher literacy, wealth, and higher grain prices were the most impacted. This suggests the Great Fear was not merely an uncontrolled emotional reaction but a response to an unsustainable situation caused by soaring grain prices and land ownership laws unfavourable to peasants.
“The Great Fear is an example of the role rumour propagation can play in driving political change,” said Stefano Zapperi, a professor in the Department of Physics at the University of Milan and a co-author of the study. “Understanding how rumours spread helps us comprehend not only the past but also how we react to crises today. The innovative approach of this research demonstrates that social phenomena, even those from over two centuries ago, can be analysed with modern scientific tools. Just as social networks spread information and disinformation today, the physical networks of the 18th century—roads, postal offices, official communications—could also trigger nationwide chain reactions.”