The Groninger ziekte (also called ‘intermittent fevers’) that broke out in 1826 was a malaria epidemic that killed 2,844 people—nearly 10% of the population of the city of Groningen.
Widespread flooding in Groningen's region during 1825 had created swamp-like conditions. The warm weather during the spring and the summer of 1826 led directly to the epidemic. The city used chlorine to combat the epidemic, becoming the first city to use chlorine for medical treatment. Meanwhile, the epidemic spread to Friesland and the Wadden Sea region.
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