Temperate climate malaria in 19th century Denmark

Mathias Mølbak Ingholt, Tzu Tung Chen, Franziska Hildebrandt, Rasmus Kristoffer Pedersen, Lone Simonsen

Research output: Contribution to journalJournal articlepeer-review


A now-extinct strain of Plasmodium vivax was endemic in northern Europe until the early 20th century. In light of the emergence of other vector borne diseases in Europe under climate change, temperate climate malaria warrants a re-examination. The purpose of this article is to characterize malaria epidemiology in 19th century Denmark. We studied the seasonality and spatial patterns of malaria morbidity and mortality in 1862-1914, and investigated environmental drivers such as soil types, clay content, altitude and associations with extreme weather events. Incidence typically peaked in May and the case fatality ratio
was 0.17%. The highest incidence occurred in coastal southeastern Denmark, where high soil clay contents and low altitude contributed to better conditions for mosquitoes. The Plasmodium parasite likely survived winters through dormancy in the human host, followed by reactivation in the spring. In 1873, a large spring epidemic occurred following flooding during a storm surge in November 1872. While the mechanism of the spring reactivation remains debated, this natural experiment suggests that the size of spring mosquito populations played a role. Our findings suggest that malaria was associated with various environmental factors, but that also extreme weather events such as floods could cause larger
malaria epidemics.
Original languageDanish
JournalMalaria Journal
Publication statusSubmitted - 2021


  • malaria
  • Denmark
  • environment
  • Plasmodium vivax
  • morbidity
  • mortality
  • historical epidemiology
  • temperate climate

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