Mass Burial Genomics Reveals Outbreak of Enteric Paratyphoid Fever in the Late Medieval Trade City Lübeck

In the Middle Ages, European settlements of all sizes were repeatedly affected by outbreaks of infectious diseases. Some of the outbreaks reached epidemic proportions, the second plague pandemic being the most notorious of all. A Late Medieval mass-burial site next to the Heiligen-Geist-Hospital (HGH) in Lubeck, a city of the Hanseatic League, contained the skeletal remains of more than 800 individuals assumed to have died of an infectious disease, most probably of the plague. However, Lubeck was ravaged by at least six pestilences in the 14 th century alone. We investigated ancient DNA extracts of 92 individuals from the HGH site to determine whether viral or bacterial pathogenic DNA was present that would help identify the cause of death. Metagenomic screening revealed evidence of an infection with Mi>Salmonella enterica subsp. enterica serovar Paratyphi C, suggesting an epidemic outbreak of enteric paratyphoid fever. A full reconstruction was possible for three S. Paratyphi C genomes that showed a close similarity to another strain from 1200 CE Norway. Based on radiocarbon dates, we determined the enteric paratyphoid fever outbreak in Lubeck to have occurred between 1360 and 1400 CE, historical records indicating the year 1367 CE as the most probable date. Our results also showed that the disease victims were people of northern and eastern European descent, confirming that Hanseatic Lubeck was an important trading centre for the Baltic region.