Diagnostic challenges in Flaviviridae infections: first human case of Usutu virus aseptic meningitis in an immunocompetent subject in Italy

Objectives Usutu virus (USUV) is a mosquito-borne Orthoflavivirus. Human USUV infections are rare and are often asymptomatic or mild; however, neuroinvasive manifestations such as meningoencephalitis have occasionally been reported. Design or Methods Diagnosis of USUV infection is challenging due to serological cross-reactivity with other flaviviruses, particularly West Nile virus, which often shares the same geographical distribution, as well as the lack of rapid and accurate serological and molecular diagnostic tools. Results Here, we report the first case of aseptic meningitis caused by USUV in an immunocompetent subject in Italy. Conclusion Highlighting the complex microbiological diagnostic pathway required to achieve an etiological diagnosis.