What is it about?
This paper revisits the 1820 plague outbreak in eastern Mallorca, Spain, using previously unexamined daily mortality records and modern epidemiological modelling. Although the outbreak has traditionally been described as bubonic plague spread mainly by rats and fleas, our results suggest a different picture. The short infectious periods, very high fatality rate, and historical clinical descriptions are more consistent with substantial pneumonic and septicemic transmission. The evidence also points to direct human-to-human spread as an important driver of the epidemic.
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Why is it important?
The 1820 Mallorca outbreak was one of the last major plague epidemics in Western Europe, making it an important case for understanding how plague spread before modern bacteriology. Our findings challenge the long-standing assumption that this epidemic followed the classic rat–flea–human model of bubonic plague. They show how human behaviour, mobility, and different clinical forms of plague may have played a much greater role than previously thought. More broadly, the study demonstrates how combining historical records with modern epidemiological methods can reveal new insights into past epidemics and improve our understanding of infectious-disease transmission.
Perspectives
This work grew from combining two complementary approaches: historical research and quantitative epidemiology. A previously overlooked archival source containing daily death counts allowed us to examine the 1820 Mallorca plague at an unusually fine scale. We analyzed these data using compartmental epidemiolocal models, together with Bayesian statistical methods, to estimate key epidemiological parameters such as the basic reproduction number (R0), the mean infectious period, and the case-fatality rate. The paper illustrates how combining historical evidence, mathematical modelling, and advanced statistical inference can uncover previously hidden features of past epidemics and challenge well-stablished narratives about how infectious diseases spread.
Pedro Puig
Universitat Autonoma de Barcelona
Read the Original
This page is a summary of: The 1820 Mallorca plague was not a classic bubonic outbreak, Proceedings of the National Academy of Sciences, August 2026, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2536892123.
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