(Vienna, 09 January 2026) A long-term study by the Center for Virology at the Medical University of Vienna shows a significant increase in cases of West Nile virus in Austria. In 2024, 37 confirmed cases were recorded, more than ever before since the virus was first detected in 2009. For the first time, northern Burgenland was particularly affected, with the virus spreading much more widely than in previous years.
The West Nile virus is transmitted in Austria by native mosquitoes. In 2024, 37 cases were documented, including 19 patients with severe symptoms who required hospital treatment. This makes 2024 the peak year for registered cases to date.
"The significant increase in cases shows that the West Nile virus is firmly established in Austria," says Judith Aberle, Professor of Virus Immunology at the Medical University of Vienna and head of the study at the Center for Virology.
New regional hotspots and virus variant
Most cases occurred in northern Burgenland. In this region, a virus variant previously known mainly from southern and south-eastern Europe was also detected for the first time. This development indicates a geographical spread of the virus within Austria.
"The fact that we are observing new regional hotspots underscores the need to remain vigilant even in areas that have been less affected so far," says Aberle. "Especially in the summer months, patients with meningitis or encephalitis should be considered for possible infection with the West Nile virus, even if they have no history of travel."
High number of unreported cases likely
Since only about one in five infected individuals develop symptoms and severe neurological diseases occur in only a small proportion, the researchers assume that there are a significant number of unrecognised infections. There is currently no effective vaccine.
Against this background, continuous monitoring is of central importance. It enables new risk areas to be identified at an early stage and appropriate responses to be made to the spread of the virus.
Research at the Center for Virology
The long-term study was conducted at the Center for Virology at the Medical University of Vienna in collaboration with AGES and analyses data from the period 2009 to 2024. Funded by the European Union under Grant Agreement No. 101191725.
Publication: Eurosurveillance
Increased incidence of human West Nile and Usutu infections in Austria, 2024: analysis of data from 2009 to 2024
David M Florian, Jeremy V Camp, Christof Jungbauer, Dirk Werber, Andreas Reich, Karin Stiasny, Stephan W Aberle, Judith H Aberle
https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2026.31.1.2500260