Retrospective Screening for Zoonotic Viruses in Encephalitis Cases in Austria, 2019–2023, Reveals Infection with Lymphocytic Choriomeningitis Virus but Not with Rustrela Virus or Tahyna Virus

Zoonotic viruses may be neglected as etiologies of meningoencephalitis in humans. We performed retrospective testing of cerebrospinal fluid from encephalitis cases in biobank material for three zoonotic or potentially zoonotic viruses: rustrela virus (<i>Rubivirus strelense</i>, <i>Matonaviridae</i>); Tahyna virus (<i>Orthobunyavirus tahynaense</i>, <i>Peribunyaviridae</i>); and lymphocytic choriomeningitis virus ("LCMV", <i>Mammarenavirus choriomeningitidis</i>, <i>Arenaviridae</i>). The cohort consisted of 443 samples, received for routine diagnostic testing year-round between January 2019 and February 2023, and were negative for herpes simplex viruses, varicella zoster virus, and enteroviruses. Using published RT-qPCR protocols, we did not detect rustrela virus or Tahyna virus in any sample. Using a herein described RT-qPCR protocol, we detected LCMV in one sample. Partial genetic sequencing of the virus suggested that the virus was locally acquired. Our study provides information about the incidence of these viruses in humans in Austria when encephalitis is suspected.