Investigators believe a single mosquito that survived a long-haul flight is to blame for the deaths of two workers at Frankfurt Airport, alongside another four who fell seriously ill, despite none of them having set foot outside Germany, let alone a malaria zone. //

Fraport, the company that operates Frankfurt Airport, has confirmed that six employees were diagnosed with malaria tropica, the most dangerous form of the disease, after falling ill between Saturday July 4 and Monday July 6. One worker died in early July. A second death was confirmed on Wednesday August 26, according to the Frankfurt health authority. The four other employees who were infected have been treated and are recovering. //

Mosquito traps have since been placed around the site, and any specimens caught are being sent to the Institute of Tropical Medicine in Antwerp, Belgium, for genetic testing to confirm the source. //

Cases like this are known in medical literature as airport malaria: an infected mosquito survives a flight from a country where the disease is endemic, then bites someone who has never left the country it lands in.

It doesn’t happen often though. Research cited by health officials has recorded fewer than 150 confirmed cases across European airports since the late 1960s