Imported aseptic meningitis due to Toscana virus infection in Austria since 2006, including a case series from 2023

Toscana virus (TOSV) is an emerging sandfly-borne virus, causing meningitis and encephalitis in Mediterranean and Middle Eastern regions. Only sporadic cases have been diagnosed in Austria over the past 20 years. We aim to identify and describe TOSV-associated aseptic meningitis (TOSV-AM) cases in Austria between 2006 and 2023.

We report a series of four imported cases of TOSV-AM diagnosed in Salzburg between July and September 2023, after travel to Italy. In addition, we analyzed all TOSV cases identified by the Austrian National Reference Center (2006-2018). Diagnosis was confirmed by immunoglobulin (Ig)M/G serology. Partial N-gene Sanger sequencing was performed for three cases in total.

Before the 2023 case series, we retrospectively identified a total of six TOSV-AM cases (three male and three female; median age was 43 years [22-53]). All four 2023 patients (three male and one female; median age was 45.5 years [37-50]) presented with clinical signs of meningitis, including headache, with three reporting insect bites. Lumbar puncture confirmed the diagnosis in three cases and IgM/IgG serology confirmed infection in all cases. TOSV detection by polymerase chain reaction in serum was possible in one patient, with nucleic acid sequencing identifying a lineage B strain. Previously diagnosed case patients were identified as lineage A.

We report a total of 10 serologically confirmed cases of TOSV-AM in Austria since 2006. Despite evidence of growing incidence of TOSV circulation in neighboring countries, this is the first well-characterized case series in Austria. Considering the recent rise in TOSV cases in endemic regions, likely driven by climate change and urbanization, imported TOSV-AM cases in Austria may increase in the future.