Malaria cases in Europe are increasing from an unexpected source: infected mosquitoes being transported on planes and in luggage, rather than from travelers returning from endemic areas.

A recent study cautions against the growing threat of "airport" and "luggage" malaria, commonly called Odyssean malaria where mosquitoes carrying the malaria parasite are unknowingly transported to non-endemic areas, sparking local infections.

The latest study published in Eurosurveillance identified 145 cases of Odyssean malaria in five years since 2018. Of these, 105 were classified as airport malaria, and 32 as luggage malaria, and the investigators could not distinguish between the two types.

While airport malaria occurs when an infected mosquito transported by plane bites someone at or near the airport, luggage malaria happens when the mosquito travels in baggage and bites a person away from the airport.

Since malaria was eradicated in Western Europe in the 1970s, over 99% of cases are now related to travel. Locally acquired malaria is rare and falls into three categories: introduced cases, where a local mosquito becomes infected by someone who traveled; induced cases, where malaria is spread without a mosquito bite; and airport or luggage malaria, caused by mosquitoes transported from endemic areas.

"While airport and luggage malaria cases are rare, reports in Europe have increased, highlighting the need for effective prevention measures and a more structured surveillance of cases in Europe. Prevention measures already in place such as aircraft disinfection should be assessed for compliance and effectiveness," the researchers noted in the study.

The researchers found that most cases of airport malaria were reported in France (52), followed by Belgium (19) and Germany (9). Also, six French airports were linked to airport malaria cases, more than in any other country. They are: Paris Charles de Gaulle, Marseille Provence, Nice Côte d'Azur, Paris–Le Bourget, Paris-Orly, and Toulouse-Blagna.

While examining cases around airports, Paris Charles de Gaulle in France reported the highest number with 32 cases, followed by Brussels Airport in Belgium with 18, Frankfurt Airport in Germany with 8, and both Geneva Airport in Switzerland and Luxembourg Airport with 5 each.

Two-thirds of luggage malaria cases were reported in France (23), followed by Italy (3) and Germany (3). Nine cases were linked to specific airports, with Paris Charles de Gaulle being the most frequently mentioned.

"Several factors may contribute to the observed increase, including changes in aircraft disinfection practices, favorable climatic conditions near airports in Europe, heightened public awareness, and changes in direct air traffic to malaria-endemic countries," the researchers wrote.

According to another study published in 2021, in PMC journal, Odyssean malaria has seen an unprecedented surge over the past decade. "From 2010 to 2020, the number of cases in Europe was 7.4 times higher than that recorded during the 2000–2009 decade. This increase may be associated with climate change, increased international trade, the decline of aircraft disinfection, as well as delays in case diagnosis and treatment," the researchers wrote.

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