German health officials are seeking to reassure the public after two workers at the country’s biggest airport died of malaria.

Mosquito traps have been set up at Frankfurt airport and a mosquito monitoring process is under way. A detailed investigation is being conducted to clarify how the workers contracted the disease.

Since last month, six people are known to have caught malaria tropica – the most dangerous form of the disease – in connection with their work at the airport.

Of the two that have died, one began getting sick at the start of July, the other in mid-August. The four other people who were infected have been treated in hospital but are now out of danger, according to Frankfurt’s public health department.

Letters have been sent to all airport workers to raise awareness about symptoms and urge vigilance. Doctors are being warned to watch out for patients with unexplained fever who work in and around the airport.

In a statement on its website, the health department acknowledged the existence of ‘airport malaria’ – where mosquitoes from malaria-endemic areas are transported in flight cabins or in baggage holds.

They said that because this was “a very rare occurrence” malaria could easily be overlooked and diagnosis delayed, increasing the chance of death. They said human-to-human transmission was not possible.

The Robert Koch Institute, which is responsible for disease control and prevention in Germany, believes the Frankfurt infection was transmitted by an Anopheles stephensi mosquito imported by plane.

spokesperson for Fraport, which operates the airport, confirmed that mosquito traps had been set up in and around the site and that mosquitoes had been caught. These are being examined in a tropical medicine laboratory in Antwerp, Belgium.

Peter Tinnemann, the head of Frankfurt’s health department, told the broadcaster Hessische Rundfunk: “The mosquito is probably already dead.”

He said that higher temperatures in Germany increased the likelihood of mosquitoes surviving for extended periods but the risk to the population of Frankfurt was low.

“Not everyone should assume that just because they have a headache, fever and nonspecific symptoms they are now infected with malaria because of the case at the airport,” he added.

But he said the rise in malaria cases made it necessary to check whether existing measures, including the disinfection of aircraft and removing breeding grounds for mosquitos, were being correctly followed.

A study that set out to record all cases of airport and baggage malaria in Europe from 1969 to 2024 found 145 instances, nine of them in Germany.

The Robert Koch Institute said Germany’s last outbreak of airport malaria was also at Frankfurt, in 2023, when a single documented infection was successfully treated.

Around 90% of all malaria cases occur in sub-Saharan Africa. Countries from this region with direct flight connections to Frankfurt include Ethiopia, Kenya, Nigeria and Tanzania, all of which have a high to widespread malaria risk. Namibia and South Africa also have direct flights but are considered to be moderate to low risk.