Europe is experiencing increasing prevalence of arbovirus diseases – those transmitted by arthropod vectors such as mosquitoes, ticks, or sand flies. These diseases, including dengue, chikungunya, and Zika, have traditionally been endemic to teh tropical and subtropical regions of South America, the Caribbean, Africa, and Asia.Their frequency and scale have increased globally in the past two decades, and the geographic range of transmission has expanded into areas previously unaffected, including non-endemic regions in Europe.
While most cases are imported,mosquito species and ticks are establishing themselves further northwards and westwards in Europe. According to the European Centre for Disease Prevention and Control (ECDC), between 2021 and 2024, the number of autochthonous (locally acquired) dengue outbreaks and cases increased considerably, and chikungunya and Zika infections have also now been reported in Mediterranean regions.
Arbovirus diseases Becoming More Common
Tamás Bakonyi, ECDC principal expert on vector-borne and zoonotic diseases, told Medscape Medical News that arbovirus diseases have become more common in Europe due to a combination of environmental, biological, and societal factors.
Climate conditions can change the environment in which infectious diseases thrive, contributing to their increase and impact, he said. Rising temperatures, milder winters, more frequent extreme weather events, and changing rainfall patterns may create more favorable conditions for the transmission of several vector-, food-, and waterborne diseases.
“Vector-borne diseases like dengue,chikungunya virus disease,West Nile virus infections,Lyme borreliosis,and tick-borne encephalitis are especially sensitive to changes in temperature,humidity,and rainfall,” he explained. Warmer temperatures increase mosquito and tick survival and shorten pathogen incubation times, which in turn accelerates disease transmission cycles.
Most Cases Imported
International travel has led to the importation of arboviruses from endemic regions to Europe,Bakonyi said.This underlies most reported arbovirus infections in Europe but may spark local outbreaks. The ECDC collects data on imported cases on an annual basis. Its latest interactive surveillance atlas, for the year 2023, showed across the EU:
- Dengue: 5027 travel-associated cases vs 129 locally acquired cases.
- Chikungunya: 320 imported cases including in Spain (191), Germany (44), and France (39), with no reported locally acquired cases.
- Zika virus infection: 79 travel-associated cases with none locally acquired.
In addition, the ECDC collects seasonal data over the summer on locally acquired cases of various arboviral diseases. Its latest communicable disease threats surveillance for the week ending August 01, 2025, showed:
- Locally acquired dengue in three European countries in 2025 so far: France (6, including 2 new cases since the previous week), Italy (3), and Portugal (2 in Madeira).
- Locally acquired chikungunya in France (49) and Italy (2) so far during 2025.
- Up to 30 July,Crimean-Congo hemorrhagic fever cases were reported in Greece (2) and Spain (2).
- Up to 30 July, human cases of West Nile virus infection were reported in Bulgaria, France, Greece, Italy, and Romania.