Investigation of an airport-associated cluster of falciparum malaria in Frankfurt, Germany

Autochthonous malaria infections in non-endemic areas may lead to delayed diagnosis. Genomic analysis of Plasmodium DNA can assist in establishing the geographical origin and control of airport malaria.We describe the clinical characteristics as well as epidemiological and molecular investigations in a cluster of airport malaria cases.Three Frankfurt International Airport employees without relevant travel histories were diagnosed with Plasmodium falciparum malaria in Germany, during the summer of 2022. We conducted epidemiological and entomological investigations to identify the source of the outbreak. We performed whole genome sequencing to investigate relatedness of the Plasmodium genomes obtained from the cases and to predict the parasite origin, using principal component analysis and identity-by-descent analysis.Three employees developed symptoms on July 6th. Two cases were diagnosed with malaria tropica within one week, and a third after 10 weeks. All three patients recovered fully. Screening of airport employees did not identify additional cases. There had been no recent direct flights from West Africa to Frankfurt. No vector mosquitoes could be trapped. Genomic analysis of the Plasmodium isolates obtained from the employees showed that high relatedness parasites and positioned the geographical origin closest to Ghana.