Two workers at Germany's Frankfurt airport who caught malaria from a mosquito thought to have arrived on a plane have died, the city's health authority said Wednesday.

Airport officials had earlier said one employee had perished, with six workers infected.

The Robert Koch Institute (RKI) said an imported Anopheles mosquito carried over by an aircraft was the likely cause.

The other four infected employees were being treated in hospital, said an airport spokesman.

According to the RKI, Germany's last outbreak of airport-based malaria was in 2023. The rarity of the condition means diagnosis can be delayed, increasing the chances of severe symptoms.

Mosquito traps installed

The other employees are being treated, the airport spokesman said, adding that mosquito traps have been installed at the airport.

The Institute of Tropical Medicine in Antwerp, Belgium, said it would analyse the malaria parasites in the patients' blood samples.

Caused by parasites spread via Anopheles mosquitoes, malaria can cause symptoms including nausea, headache and intense waves of fever and chills.

The disease causes hundreds of thousands of deaths a year, mostly in sub-Saharan Africa.

Treatments exist and patients caught early with the disease usually make a complete recovery.