Identifying signature features of epidemic diseases from 19th century all-cause mortality data

Abstract

Deadly epidemics leave distinct marks on all-cause mortality. When cause-specific health data is unavailable, studies of all-cause mortality may be necessary for understanding epidemic and pandemic diseases in history. We identify and catalog every major epidemic in Denmark during the hundred-year period between 1814 and 1915, based on a recently digitized and compiled dataset of all 4 million burials in the period. Despite the dataset lacking specific cause-of-death information, we were able to determine plausible etiology for the majority of 418 identified mortality crises with more than 50 excess deaths. This was done using epidemiological methods, data analysis, consultation with historical sources, and investigation of the signature features of age-patterns, seasonality, timing, and geography. The identified epidemics include, among others, pandemic influenza, cholera-outbreaks in 1853 and 1857 and annually repeating epidemics in 1826-1832. While these epidemics have been discussed elsewhere, our work presents a different view of these epidemics, based solely on all-cause mortality. Some of the identified epidemics were caused by pathogens that still affect us in modern times. In low-income modern settings where representative population health data may be unavailable, the use of mortality data to determine the signature features may guide policy and improve future mitigation strategies.