Modeling the spatio-temporal spread of cholera in France in 1892.

From an historical perspective, it is important to understand how past epidemics spread; but such a task is complicated by limited data availability. Here, using unique digitized historical data, we characterized the patterns and drivers of spread of the last major French cholera epidemic in 1892. We found that epidemic dynamics are well captured by a standard gravity model, highlighting the key contribution of human mobility to cholera spread. Our findings also underscore the crucial role of major commercial ports that acted both as points of introduction from external sources (multiple introductions were estimated) and as local transmission hubs (transmission rates increased by a factor of 10 around ports). We also estimated a 2.5-fold increase in transmission rates in mid-August, compensated by a reduction in the duration of infectivity of municipalities, highlighting both seasonality in transmission and the effectiveness of control measures implemented in 1892. Applying modern analytical techniques to historical outbreaks enhances our understanding of past pandemics.