Examining trends in epidemic typhus using historical texts.

Background objectives: Although associated with conflict, epidemic typhus was endemic across Europe into the modem period. The extent of the problem it caused is uncertain as record keeping in the most affected socioeconomic groups was rare. Google Ngram Viewer details the frequency of word usage in written language over time. The objective was to examine whether use of the word typhus reflected potential patterns in epidemic typhus.

Methods: The frequency of the word 'typhus' was used in British English was studied between 1800 and 2019 and trends were examined.

Results: Clear differences in word usage were apparent; use increased throughout the 19 th century corresponding to increasing industrialization. Peaks coinciding with World Wars 1 and 2 were apparent. Strong correlations with the words "conflict", "warfare" and "industry" were seen. Mean shifts corresponded to public health legislation in the UK and the introduction of antibiotics.

Interpretation conclusion: This study illustrates how examination of word usage can illuminate aspects of disease occurrence where official data sources are lacking.